MAX7370ETG+T - Maxim Integrated - Datasheet.Technology

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

19-5950; Rev 2; 5/15

Typical Operating Circuit

Ordering Information appears at end of data sheet.

For related parts and recommended products to use with this part,

refer to www.maximintegrated.com/MAX7370.related.

General Description

The MAX7370 I2C-interfaced peripheral provides micro-

processors with management of up to 64 key switches,

with optional GPIO and PWM-controlled LED drivers.

The key-switch drivers interface with metallic or resistive

switches with on-resistances up to 5kI. Key inputs are

monitored statically, not dynamically, to ensure low-EMI

operation. The IC features autosleep and autowake

modes to further minimize the power consumption of

the device. The autosleep feature puts the device in a

low-power state (1µA typ) after a timeout period. The

autowake feature configures the device to return to

normal operating mode from sleep upon a keypress.

The key controller debounces and maintains a FIFO

buffer of keypress and release events (including auto-

repeat, if enabled). An interrupt (INT) output can be

configured to alert keypresses, as they occur, or at the

maximum rate.

The same index rows and columns in the device can be

used as a direct logic-level translator.

If the device is not used for key-switch control, all

keyboard pins can be used as GPIOs. Each GPIO can

be programmed to one of the two externally applied

logic voltage levels. Four column ports (COL7–COL4)

can also be configured as LED drivers that feature

constant-current and PWM intensity control. The maximum

constant-current level for each open-drain LED port is

20mA. The intensity of the LED on each open-drain port

can be individually adjusted through a 256-step PWM

control.

The device is offered in a 24-pin (3.5mm x 3.5mm) TQFN

package with an exposed pad, and small 25-bump

(2.159mm x 2.159mm) wafer-level package (WLP) for

cell phones, pocket PCs, and other portable consumer

electronic applications.

The device operates over the -40°C to +85°C extended

temperature range.

Applications

Cell Phones

Notebooks

PDAs

Handheld Games

Portable Consumer Electronics

Features

S Monitors Up to 64 Keys

S Integrated High-ESD Protection

±8kV IEC 61000-4-2 Contact Discharge

±15kV IEC 61000-4-2 Air-Gap Discharge

S Keyscan Uses Static Matrix Monitoring for

Low-EMI Operation

S Four LED Driver Pins on COL7–COL4

S 5V Tolerant, Open-Drain I/O Ports Capable of

Constant-Current LED Drive

S 256-Step PWM Individual LED Intensity-Control

Accuracy

S Individual LED Blink Rates and Common LED

Fade In/Out Rates from 256ms to 4096ms

S FIFO Queues Up to 16 Debounced Key Events

S User-Configurable Keypress and Release

Debounce Time (2ms to 32ms)

S Key-Switch Interrupt (INT) on Each Debounced

Event/FIFO Level, or End-of-Definable Time Period

S 1.62V to 3.6V Operating Supply Voltage

S Individually Programmable GPIOs to Two Logic

Levels

S 8-Channel Individual Programmable Level

Translators

S Provides Optional GPIOs on all ROW_ and COL_

Pins

S Supports Hot Insertion

S 400kbps, 5.5V Tolerant I2C Serial Interface with

Selectable Bus Timeout

EVALUATION KIT AVAILABLE

+5V

+1.8V

VCC

+2.6V

VLA

COL[0:3]

32 KEYS

ROW[0:7] 8

GND

COL4

COL5

COL6

COL7

I/O

SDA

SCL

AD0

MCU

MAX7370

INT

For pricing, delivery, and ordering information, please contact Maxim Direct

at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

2Maxim Integrated

VCC, VLA to GND ....................................................-0.3V to +4V

COL3–COL0, ROW7–ROW0 to GND ....... -0.3V to (VCC + 0.3V)

COL7–COL4 to GND ............................................... -0.3V to +6V

SDA, SCL, AD0, INT to GND ..................................-0.3V to +6V

VLA to VCC ...........................................................-0.3V to +2.3V

DC Current on COL7–COL4 to GND .................................25mA

DC Current on COL3–COL0, ROW7–ROW0 to GND ...........7mA

VCC, VLA, GND Current .....................................................80mA

DC Current VCC, VLA to COL3–COL0, ROW7–ROW0 .........5mA

Continuous Power Dissipation (TA = +70°C)

24-Pin TQFN (derate 15.4mW/°C above +70°C) ......1229mW

25-Bump WLP (derate 19.2mW/°C above +70°C) ......850mW

Operating Temperature Range .......................... -40°C to +85°C

Junction Temperature .....................................................+150°C

Storage Temperature Range ............................ -65°C to +150°C

Lead Temperature (TQFN) (soldering, 10s) ...................+300°C

Soldering Temperature (reflow) ......................................+260°C

24 TQFN

Junction-to-Ambient Thermal Resistance (BJA) .........65.1°C/W

Junction-to-Case Thermal Resistance (BJC) ................ 5.4°C/W

25 WLP

Junction-to-Ambient Thermal Resistance (BJA) ........... 52°C/W

ABSOLUTE MAXIMUM RATINGS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-

tion of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute

maximum rating conditions for extended periods may affect device reliability.

PACKAGE THERMAL CHARACTERISTICS (Note 1)

ELECTRICAL CHARACTERISTICS

(VCC = 1.62V to 3.6V, TA = -40NC to +85NC, unless otherwise noted. Typical values are at VCC = 3.3V, TA = +25NC.) (Notes 2, 3)

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer

board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Operating Supply Voltage VCC 1.62 3.3 3.6 V

Second Logic Supply VLA VCC 3.3 3.6 V

Operating Supply Current ICC

All key switches open, oscillator

running 50 65

N keys pressed 50 + 28 O N

Sleep-Mode Supply Current ISL Not using GPO or LED configuration 1.8 3 FA

POR Threshold VPOR 1.2 V

KEY-SWITCH SPECIFICATIONS

Key-Switch Source Current IKEY 28 40 FA

Key-Switch Source Voltage VKEY 0.45 0.5 V

Key-Switch Resistance RKEY (Note 4) 5 kI

Startup Time from Sleep tSTART 2 2.7 ms

GPIO SPECIFICATIONS

External Supply Voltage

COL7–COL4 (LED Drivers) VLED 5 V

LED Port-to-Port Sink Current Variation VCC = 3.3V, VOL = 1V, TA = +25NC,

10mA output mode Q1.5 Q2.4 %

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

3Maxim Integrated

ELECTRICAL CHARACTERISTICS (continued)

(VCC = 1.62V to 3.6V, TA = -40NC to +85NC, unless otherwise noted. Typical values are at VCC = 3.3V, TA = +25NC.) (Notes 2, 3)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

10mA Port Sink Current

COL7–COL4 IOL

VOL = 1V TA = +25NC8.6 11.4

VCC = 3.3V 9.04 10 10.96

VOL = 0.5V VCC = 3.6V,

TA = +25NC9.5

20mA Port Sink Current

COL7–COL4 IOL

VOL = 1V TA = +25NC18.13 21.52

VCC = 3.3V 18.47 20 21.34

VOL = 0.5V VCC = 3.6V,

TA = +25NC19.05

Input High Voltage

COL_, ROW_ VIH VS = VCC or VLA depending on

reference logic level setting

0.7 O VSV

Input Low Voltage

COL_, ROW_ VIL 0.3 O VSV

Input Leakage Current

COL3–COL0, ROW_ ILEAKAGE Input voltage = VCC or VGND -2 +2 FA

Input Leakage Current

COL7–COL4 ILEAKAGE Input voltage = 5V -1 +1 FA

Input Capacitance

COL _, ROW_ CIN 20 pF

Maximum Allowable Load Capacitance

for Keyscan Function N keys pressed simultaneously 500 pF

Output Low Voltage

COL_, ROW_ VOL

VCC = 1.62V and ISINK = 2.5mA 50 100 mV

VCC = 1.62V and ISINK = 5mA 80 250

Output High Voltage

COL3–COL0, ROW_ VOH

VCC = 1.62V and ISOURCE = 2.5mA VCC -

120

VCC -

40 mV

VCC = 1.62V and ISOURCE = 5mA VCC -

250

VCC -

Output Logic-Low Voltage

(INT)VOL ISINK = 6mA 0.6 V

PWM Frequency fPWM Derived from oscillator clock 500 Hz

SERIAL-INTERFACE SPECIFICATIONS

Input High Voltage

SDA, SCL, AD0 VIH 0.7 O VCC V

Input Low Voltage

SDA, SCL, AD0 VIL 0.3 O VCC V

Input Leakage Current

SDA, SCL, AD0 ILEAKAGE Input voltage = 5.5V or VGND -1 +1 FA

Output Logic-Low Voltage

SDA VOL ISINK = 6mA 0.6 V

Input Capacitance

SDA, SCL, AD0 CIN (Notes 4, 5) 10 pF

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

4Maxim Integrated

ELECTRICAL CHARACTERISTICS (continued)

(VCC = 1.62V to 3.6V, TA = -40NC to +85NC, unless otherwise noted. Typical values are at VCC = 3.3V, TA = +25NC.) (Notes 2, 3)

Note 2: All parameters are tested at TA = +25°C. Specifications over temperature are guaranteed by design.

Note 3: All digital inputs at VCC or GND.

Note 4: Guaranteed by design.

Note 5: CB = total capacitance of one bus line in pF. tR and tF measured between 0.8V and 2.1V.

Note 6: A master device must provide a hold time of at least 300ns for the SDA signal (referred to VIL of the SCL signal) to bridge

the undefined region of SCL’s falling edge.

Note 7: ISINK = 6mA. CB = total capacitance of one bus line in pF. tR and tF measured between 0.8V and 2.1V.

Note 8: Input filters on the SDA, SCL, and AD0 inputs suppress noise spikes less than 50ns.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

I2C TIMING SPECIFICATIONS

SCL Serial-Clock Frequency fSCL

Bus timeout enabled 0.05 400 kHz

Bus timeout disabled 0 400

Bus Free Time Between a STOP and

START Condition tBUF 1.3 Fs

Hold Time (Repeated) START Condition tHD, STA 0.6 Fs

Repeated START Condition Setup Time tSU, STA 0.6 Fs

STOP Condition Setup Time tSU, STO 0.6 Fs

Data Hold Time tHD, DAT (Note 6) 0.9 Fs

Data Setup Time tSU, DAT 100 ns

SCL Clock Low Period tLOW 1.3 Fs

SCL Clock High Period tHIGH 0.7 Fs

Rise Time of Both SDA and SCL

Signals, Receiving tR(Notes 4, 5) 20 +

0.1CB300 ns

Fall Time of Both SDA and SCL Signals,

Receiving tF(Notes 4, 5) 20 +

0.1CB300 ns

Fall Time of SDA Signal, Transmitting tF, TX (Notes 4, 7) 20 +

0.1CB250 ns

Pulse Width of Spike Suppressed tSP (Notes 4, 8) 50 ns

Capacitive Load for Each Bus Line CB(Note 4) 400 pF

Bus Time Out tTIMEOUT 14 19 27 ms

ESD PROTECTION

ROW7–ROW0, COL7–COL0

IEC 61000-4-2 Air-Gap Discharge Q15

IEC 61000-4-2 Contact Discharge Q8

All Other Pins Human Body Model Q2.5 kV

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

5Maxim Integrated

Typical Operating Characteristics

(VCC = 2.5V, VLA = 2.5V, TA = +25NC, unless otherwise noted.)

GPO OUTPUT LOW VOLTAGE

vs. SINK CURRENT (COL7–COL4)

MAX7370 toc01

SINK CURRENT (mA)

GPO OUTPUT LOW VOLTAGE (mV)

18161412108642

100

120

020

VCC = 2.4V

TA = +85°C

TA = +25°C

TA = -40°C

GPO OUTPUT LOW VOLTAGE

vs. SINK CURRENT (COL7–COL4)

MAX7370 toc02

SINK CURRENT (mA)

GPO OUTPUT LOW VOLTAGE (mV)

18161412108642

100

120

020

VCC = 3.0V

TA = +85°C

TA = +25°C

TA = -40°C

GPO OUTPUT LOW VOLTAGE

vs. SINK CURRENT (COL7–COL4)

MAX7370 toc03

SINK CURRENT (mA)

GPO OUTPUT LOW VOLTAGE (mV)

18161412108642

100

120

020

VCC = 3.6V

TA = +85°C

TA = +25°C

TA = -40°C

SUPPLY CURRENT vs. SUPPLY VOLTAGE

MAX7370 toc04

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

3.43.23.02.82.62.42.22.01.8

1.6 3.6

AUTOSLEEP = OFF

TA = +85°C

TA = +25°C

TA = -40°C

KEY-SWITCH SOURCE CURRENT

vs. SUPPLY VOLTAGE

MAX7370 toc05

SUPPLY VOLTAGE (V)

KEY-SWITCH SOURCE CURRENT (µA)

3.43.23.02.82.62.42.22.01.8

24.5

25.0

25.5

26.0

26.5

27.0

24.0

1.6 3.6

VCOL0 = 0V TA = +85°C

TA = +25°C

TA = -40°C

SLEEP-MODE SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX7370 toc06

SUPPLY VOLTAGE (V)

SLEEP-MODE SUPPLY CURRENT (µA)

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

3.43.23.02.82.62.42.22.01.81.6 3.6

TA = +85°C

TA = +25°C

TA = -40°C

CONSTANT-CURRENT GPIO OUTPUT SINK

CURRENT vs. OUTPUT VOLTAGE (COL7–COL4)

MAX7370 toc07

OUTPUT VOLTAGE (V)

CONSTANT-CURRENT GPIO OUTPUT SINK CURRENT (mA)

2.52.01.51.00.5

0 3.0

VCC = 2.4V TA = +85°C

TA = +25°C

TA = -40°C

CONSTANT-CURRENT GPIO OUTPUT SINK

CURRENT vs. OUTPUT VOLTAGE (COL7–COL4)

MAX7370 toc08

OUTPUT VOLTAGE (V)

CONSTANT-CURRENT GPIO OUTPUT SINK CURRENT (mA)

2.52.01.51.00.5

0 3.0

VCC = 3.0V TA = +85°C

TA = +25°C

TA = -40°C

CONSTANT-CURRENT GPIO OUTPUT SINK

CURRENT vs. OUTPUT VOLTAGE (COL7–COL4)

MAX7370 toc09

OUTPUT VOLTAGE (V)

CONSTANT-CURRENT GPIO OUTPUT SINK CURRENT (mA)

2.52.01.51.00.5

0 3.0

VCC = 3.6V TA = +85°C

TA = +25°C

TA = -40°C

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

6Maxim Integrated

Pin/Bump Description

Pin/Bump Configurations

PIN BUMP NAME FUNCTION

TQFN WLP

1 A2 ROW5 Row 5 Input from Key Matrix or GPIO Port

2 B2 ROW6 Row 6 Input from Key Matrix or GPIO Port

3 A3 ROW7 Row 7 Input from Key Matrix or GPIO Port

4 B3 COL7 Column 7 Output from Key Matrix or Open-Drain GPIO Port. COL7 can be configured as a

constant-current sink.

5 A4 COL6 Column 6 Output from Key Matrix or Open-Drain GPIO Port. COL6 can be configured as a

constant-current sink.

6 A5 COL5 Column 5 Output from Key Matrix or Open-Drain GPIO Port. COL5 can be configured as a

constant-current sink.

7 B4 COL4 Column 4 Output from Key Matrix or Open-Drain GPIO Port. COL4 can be configured as a

constant-current sink.

8, 23 B1, B5,

C3 GND Ground

9 C5 COL3 Column 3 Output from Key Matrix or GPIO Port

10 C4 COL2 Column 2 Output from Key Matrix or GPIO Port

11 D5 COL1 Column 1 Output from Key Matrix or GPIO Port

12 E5 COL0 Column 0 Output from Key Matrix or GPIO Port

MAX7370

TOP VIEW

(BUMP SIDE DOWN)

WLP

1234

ROW4 ROW5 ROW7 COL6 COL5

GND ROW6 COL7 COL4 GND

ROW3 ROW2 GND COL2 COL3

ROW1 VCC SDA VLA COL1

ROW0 SCL AD0 COL0

INT

TQFN

MAX7370

23456

18 17 16 15 14 13

ROW0

ROW2

ROW1

ROW3

ROW4

ROW5

ROW6

ROW7

COL7

COL6

COL5

VCC

INT

SDA

AD0

VLA

GND

COL0

*CONNECT EP TO GROUND.

COL2

COL1

COL3

COL4

GND

SCL

TOP VIEW

EP*

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

7Maxim Integrated

Pin Description (continued)

Functional Block Diagram

PIN NAME FUNCTION

TQFN WLP

13 D4 VLA Second Logic Level for GPIO Level Shifting (where VCC P VLA P 3.6V)

14 E4 AD0 Address Input. Selects up to four device slave addresses (Table 3).

15 D3 SDA I2C-Compatible, Serial-Data I/O

16 E3 SCL I2C-Compatible, Serial-Clock Input

17 E2 INT Active-Low Key-Switch Interrupt Output. INT is open-drain and requires a pullup resistor.

18 D2 VCC Positive Supply Voltage. Bypass to GND with a 0.1FF capacitor as close as possible to the device.

19 E1 ROW0 Row 0 Input from Key Matrix or GPIO Port

20 D1 ROW1 Row 1 Input from Key Matrix or GPIO Port

21 C2 ROW2 Row 2 Input from Key Matrix or GPIO Port

22 C1 ROW3 Row 3 Input from Key Matrix or GPIO Port

24 A1 ROW4 Row 4 Input from Key Matrix or GPIO Port

— — EP Exposed Pad (TQFN Only). Internally connected to GND. Connect to a large ground plane to

maximize thermal performance. Not intended as an electrical connection point.

INT

128kHz

OSCILLATOR

CONTROL

REGISTERS FIFO

BUS TIMEOUT POR

KEY-SCAN

LOGIC

ROW

DRIVES/

PUSH-

PULL GPIO

PWM

GPIO

LOGIC

ROW0

ROW1

ROW2

ROW3

ROW4

ROW5

ROW6

ROW7

COL1

COL2

COL3

COL4

COL5

COL6

COL7

LED ENABLE

I/O SUPPLY CONTROL

I2C

INTERFACE

PWM SIGNAL

VLA

VCC

AD0

SCL

SDA

CURRENT

SOURCE

COLUMN

DRIVES/

PUSH-

PULL GPIO/

LED DRIVERS

COLUMN ENABLE

GPIO ENABLE

ROW DETECT

GPIO ENABLE

CURRENT DETECT

GPIO INPUT

ROW ENABLE

GPIO INPUT

COL0

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

8Maxim Integrated

Detailed Description

The MAX7370 is a microprocessor peripheral low-noise

key-switch controller that monitors up to 64 key switches

with optional autorepeat, and key events that are pre-

sented in a 16-byte FIFO. Key-switch functionality can

be traded to provide up to 16 logic inputs. The device

also features 12 push-pull GPOs configured for digital

I/O and four open-drain GPOs configurable as constant-

current outputs for LED applications up to 5V. The device

supports a second 1.62V to 3.6V power supply for level

translation. The second logic supply voltage (VLA) must

be set equal to or higher than VCC.

The device features an automatic sleep mode and auto-

matic wakeup that further reduce supply current con-

sumption. The device can be configured to enter sleep

mode after a programmable time following a key event.

The FIFO content is maintained and can be read in sleep

mode. The device does not enter autosleep when a key

is held down. The autowake feature takes the device

out of sleep mode following a keypress. Autosleep and

autowake are enabled/disabled by programming the

configuration register (0x01).

To prevent overloading the microprocessor with too

many interrupts, interrupt requests can be triggered

after a programmable number of FIFO entries have been

exceeded, and/or after a set period of time (0x05). The

key-switch status is checked by reading the key-switch

FIFO. A 1-byte read access returns both the next key

event in the FIFO (if there is one) and the FIFO status.

Up to four of the key-switch outputs function as open-

drain GPOs capable of driving additional LEDs when the

application requires fewer keys to be scanned. For each

key-switch output used as a GPO, the number of moni-

tored key switches reduces by eight.

The device meets ESD requirements for ±8kV contact dis-

charge and 15kV Air-Gap Discharge on all key-switch pins.

Initial Power-Up

On power-up, all control registers are set to power-up

values (Table 1) and the device is in sleep mode.

Table 1. Register Address Map and Power-Up Conditions

ADDRESS

CODE (hex) READ/WRITE POWER-UP

VALUE (hex)

FUNCTION DESCRIPTION

0x00 Read only 0x3F Keys FIFO Read FIFO keyscan data out

0x01 R/W0x0B Configuration Power-down, key-release enable, autowake, and I2C

timeout enable

0x02 R/W0xFF Debounce Key debounce time setting

0x03 R/W0x00 Interrupt Key-switch interrupt and INT frequency setting

0x05 R/W0x00 Key repeat Delay and frequency for key repeat

0x06 R/W0x07 Sleep Idle time to autosleep

0x30 R/W0xFF Key-switch size Keyscan switch array size

0x31 R/W0x00 LED driver

enable LED driver enable register

0x32 R/W0xFF GPI enable GPI enable for ROW7–ROW0

0x33 R/W0xFF GPI enable GPI enable for COL7–COL0

0x34 R/W0x00 GPIO

direction 1

GPIO input/output control register 1 for

ROW7–ROW0

0x35 R/W0x00 GPIO

direction 2 GPIO input/output control register 2 for COL7–COL0

0x36 R/W0xFF GPO output

mode 1

GPO open-drain/push-pull output setting for

ROW7–ROW0

0x37 R/W0x0F GPO output

mode 2

GPO open-drain/push-pull output setting for

COL7–COL0

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

9Maxim Integrated

Table 1. Register Address Map and Power-Up Conditions (continued)

ADDRESS

CODE (hex) READ/WRITE POWER-UP

VALUE (hex)

FUNCTION DESCRIPTION

0x38 R/W0x00 GPIO supply

voltage 1

GPIO voltages supplied by VCC or VLA for

ROW7–ROW0

0x39 R/W0x00 GPIO supply

voltage 2

GPIO voltages supplied by VCC or VLA for

COL7–COL0

0x3A R/W0xFF GPIO values 1 Debounced input or output values of ROW7–ROW0

0x3B R/W0xFF GPIO values 2 Debounced input or output values of COL7–COL0

0x3C R/W0x00 GPIO level-

shifter enable GPIO direct level-shifter pair enable

0x40 R/W0x00 GPIO global

configuration GPIO global enable, GPIO reset, LED fade enable

0x42 R/W0x00 GPIO debounce ROW7–ROW0 debounce time setting

0x43 R/W0xC0 LED constant-

current setting COL7–COL4 constant-current output setting

0x45 R/W0x00 Common PWM Common PWM duty-cycle setting

0x48 Read only 0x00 I2C timeout flag I2C timeout since last POR

0x50 R/W0x00 COL4 PWM

ratio COL4 individual duty-cycle setting

0x51 R/W0x00 COL5 PWM

ratio COL5 individual duty-cycle setting

0x52 R/W0x00 COL6 PWM

ratio COL6 individual duty-cycle setting

0x53 R/W0x00 COL7 PWM

ratio COL7 individual duty-cycle setting

0x54 R/W0x00 COL4 LED

configuration

COL4 interrupt, PWM mode control, and blink-

period settings

0x55 R/W0x00 COL5 LED

configuration

COL5 interrupt, PWM mode control, and blink-

period settings

0x56 R/W0x00 COL6 LED

configuration

COL6 interrupt, PWM mode control, and blink-

period settings

0x57 R/W0x00 COL7 LED

configuration

COL7 interrupt, PWM mode control, and blink-

period settings

0x58 R/W0xFF Interrupt

mask 1 Interrupt mask for ROW7–ROW0

0x59 R/W0xFF Interrupt

mask 2 Interrupt mask for COL7–COL0

0x5A R/W0x00 GPI trigger

mode 1

GPI edge-triggered detection setting for

ROW7–ROW0

0x5B R/W0x00 GPI trigger

mode 2

GPI edge-triggered detection setting for

COL7–COL0

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

10Maxim Integrated

Keyscan Controller

Key inputs are scanned statically, not dynamically, to

ensure low-EMI operation. Since inputs only toggle in

response to switch changes, the key matrix can be

routed closer to sensitive circuit nodes.

The keyscan controller debounces and maintains a FIFO

buffer of keypress and release events (including auto-

repeated keypresses, if autorepeat is enabled). Table 2

shows the key-switch order. The user-programmable key-

switch debounce time and autosleep timer are derived

from the 64kHz clock, which in turn is derived from the

128kHz oscillator. Time delay for autorepeat and key-

switch interrupt is based on the key-switch debounce

time. There is no limitation for the number of keys pressed

simultaneously as long as no ghost keys are generated.

If the application requires fewer keys to be scanned, the

unused key-switch ports can be configured as GPIOs.

Keys FIFO Register (0x00)

The Keys FIFO register contains the information pertain-

ing to the status of the keys FIFO, as well as the key events

that have been debounced. See Table 7. Bits D[5:0]

denote which of the 64 keys have been debounced and

the keys are numbered as shown in Table 2.

Bit D7 indicates if there is more data in the FIFO, except

when D[5:0] indicate key 63 or key 62. When D[5:0] indi-

cate key 63 or key 62, the host should read the FIFO one

more time to determine whether there is more data in the

FIFO. Use key 62 and key 63 for rarely used keys. D6

indicates if it is a keypress or release event, except when

D[5:0] indicate key 63 or key 62.

Reading the keyscan FIFO clears the interrupt (INT),

depending on the setting of bit D5 in the configuration

Configuration Register (0x01)

The Configuration register controls the I2C bus time-

out feature, enables key-release detection, enables

autowake, and determines how INT is deasserted. Write

to bit D7 to put the device into sleep mode or operating

mode. Autosleep and autowake, when enabled, also

change the status of D7. See Table 8.

Debounce Register (0x02)

The Debounce register sets the keypress and key-

release time for each debounce cycle. Bits D[3:0] set the

debounce time for keypresses, while bits D[7:4] set the

debounce time for key releases. Both debounce times

are configured in increments of 2ms starting at 2ms and

ending at 32ms. See Table 9.

Interrupt Register (0x03)

The Interrupt register contains information related to the

settings of the interrupt request function, as well as the sta-

tus of the INT output. If bits D[7:0] are set to 0x00, the INT

is disabled. There are two types of interrupts, the FIFO-

based interrupt and time-based interrupt. Set bits D[4:0]

to assert interrupts at the end of the selected number of

debounce cycles following a key event. See Table 10.

This number ranges from 1–31 debounce cycles. Setting

bits D[5:7] set the FIFO-based interrupt when there are

2–14 key events stored in the FIFO. Both interrupts can be

configured simultaneously and INT asserts depending on

which condition is met first. INT deasserts depending on

the status of bit D5 in the configuration register.

Autorepeat Register (0x05)

The device autorepeat feature notifies the host that at

least one key has been pressed for a continuous period.

The Autorepeat register enables or disables this feature,

sets the time delay after the last key event before the key-

repeat code (0x7E) is entered into the FIFO, and sets

Table 2. Key-Switch Mapping

PIN COL0 COL1 COL2 COL3 COL4 COL5 COL6 COL7

ROW0 KEY 0 KEY 8 KEY 16 KEY 24 KEY 32 KEY 40 KEY 48 KEY 56

ROW1 KEY 1 KEY 9 KEY 17 KEY 25 KEY 33 KEY 41 KEY 49 KEY 57

ROW2 KEY 2 KEY 10 KEY 18 KEY 26 KEY 34 KEY 42 KEY 50 KEY 58

ROW3 KEY 3 KEY 11 KEY 19 KEY 27 KEY 35 KEY 43 KEY 51 KEY 59

ROW4 KEY 4 KEY 12 KEY 20 KEY 28 KEY 36 KEY 44 KEY 52 KEY 60

ROW5 KEY 5 KEY 13 KEY 21 KEY 29 KEY 37 KEY 45 KEY 53 KEY 61

ROW6 KEY 6 KEY 14 KEY 22 KEY 30 KEY 38 KEY 46 KEY 54 KEY 62

ROW7 KEY 7 KEY 15 KEY 23 KEY 31 KEY 39 KEY 47 KEY 55 KEY 63

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

11Maxim Integrated

the frequency at which the key-repeat code is entered

into the FIFO thereafter. The key being pressed is not

entered again into the FIFO. Bit D7 specifies whether

the autorepeat function is enabled with 0, denoting

autorepeat disabled, and 1, denoting autorepeat

enabled. Bits D[3:0] specify the autorepeat delay in

terms of debounce cycles, ranging from eight debounce

cycles to 128 debounce cycles. See Table 11. Bits D[6:4]

specify the autorepeat rate or frequency ranging from

4–32 debounce cycles.

Only one autorepeat code is entered into the FIFO,

regardless of the number of keys pressed. The autore-

peat code continues to be entered in the FIFO at the

frequency set by bits D[3:0] until another key event is

recorded. Following the key-release event, if any keys are

still pressed, the device restarts the autorepeat sequence.

Autosleep Register (0x06)

Autosleep puts the device in sleep mode to draw minimal

current. When enabled, the device enters sleep mode

if no keys are pressed for the autoshutdown time. See

Table 12.

Key-Switch Array Size Register (0x30)

Bits D[7:4] set the row size of the key-switch array, and

bits D[3:0] set the column size of the key-switch array.

See Table 13. Set the bits to 0 if no key switches are

used. The key-switch array should be connected begin-

ning at ROW0 and COL0. If not used as a key-switch

matrix pin, then the pin can function as a GPIO port.

Key-Switch Sleep Mode

In sleep mode, the device draws minimal current. Switch-

matrix current sources are turned off and pulled up to

VCC. When autosleep is enabled, key-switch inactivity

for a period longer than the autosleep time puts the part

into sleep mode (FIFO data is maintained). Writing a 1 to

D7 or a keypress can take the device out of sleep mode.

Bit D7 in the configuration register gives the sleep-mode

status and can be read any time.

Autowake

Keypresses initiate autowake and the device goes into

operating mode. Keypresses that autowake the device

are not lost. When a key is pressed while the device is in

sleep mode, all analog circuitry, including switch-matrix

current sources, turn on in 2ms. The initial key needs to

be pressed for 2ms plus the debounce time to be stored

in the FIFO. Write a 0 to bit D1 in the configuration regis-

ter (0x01) to disable autowake.

FIFO Overflow

The FIFO overflow status occurs when the FIFO is full

(16 bytes) and additional events occur. If key release is

disabled, then the FIFO overflow status occurs when the

FIFO is full and not upon additional key events. When

the FIFO is overflowed, the first byte read from the FIFO

buffer is the overflow byte (0x7F). The order of the

original 16 bytes of event data is preserved, but further

events could be lost. When the FIFO is full, if the 18th

key event is a key release, then the FIFO overflow status

is removed.

GPIOs

The device has 16 GPIO ports, four of which have LED

control functions. The ports can be used as logic inputs

or logic outputs. COL7–COL4 are also configurable as

constant-current PWM LED drivers. Each port’s logic

level is referenced to VCC or VLA. The GPIO ports’ inputs

can also be debounced. When in PWM mode, the ports

are set up to start their PWM cycle in 45N phase incre-

ments. This prevents large current spikes on the LED

supply voltage when driving multiple LEDs.

LED Driver Enable Register (0x31)

Bits D[3:0] correspond to COL7–COL4 on the device.

Set the corresponding bit to 1 for enabling the LED driver

circuitry and 0 for normal GPIO function. See Table 14.

GPIO Direction 1 and 2 Registers (0x34, 0x35)

These registers configure the pins as an input or an output

port. GPIO Direction 1 register bits D[7:0] correspond with

ROW7–ROW0. See Table 15. GPIO Direction 2 register

bits D[7:0] correspond with COL7–COL0. See Table 16.

Set the corresponding bit to 0 to configure as input and 1

to configure as output.

When the port is initially programmed as an input, there

is a delay of one debounce period prior to detecting

a transition on the input port. This is to prevent a false

interrupt from occurring when changing a port from an

output to an input.

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

12Maxim Integrated

GPO Output Mode 1 and 2 Registers (0x36, 0x37)

These registers configure the pin as an open-drain

or push-pull output. GPO Output Mode 1 register bits

D[7:0] correspond with ROW7–ROW0. See Table 17.

GPO Output Mode 2 register bits D[7:0] correspond with

COL7–COL0. See Table 18. Set the corresponding bit to

0 to configure the output mode as open-drain and 1 to

configure the output mode as push-pull.

GPIO Supply Voltage 1 and 2

Registers (0x38, 0x39)

These registers configure input and output voltages to

be referenced to VCC or VLA. GPIO Supply Voltage 1

Table 19. GPIO Supply Voltage 2 register bits D[7:0] cor-

respond with COL7–COL0. See Table 20. Set the bit to 0

for input/output voltages referenced to VCC or set the bit

to 1 for the input/output voltage referenced to VLA.

GPIO Values 1 and 2 Registers (0x3A, 0x3B)

The GPIO Values 1 and 2 registers contain the debounced

input data for all the GPIOs for ROW7–ROW0 and COL7–

COL0, respectively. See Tables 21 and 22. There is one

debounce period delay prior to detecting a transition on

the input port. This prevents a false interrupt from occur-

ring when changing a port from an output to an input. The

GPIO Values 1 and 2 registers report the state of all input

ports regardless of any interrupt mask settings.

When writing to the GPIO Values 1 and 2 registers, the

corresponding port voltage is set high when written 1 or

cleared when written 0. Reading the port when config-

ured as an output always returns the value 0 for the cor-

responding port regardless of the output value.

GPIO Level-Shifter Enable Register (0x3C)

Enabling bit D_ in this register enables the direct level

shifter between GPIO pins COL_ and ROW_. See

Table 23. As an example, setting D5 to logic-high

enables level shifting between COL5 and ROW5. The

direction of the level shifter is controlled by the GPIO

Direction 2 register (0x35). When setting the correspond-

ing bit in the GPIO Direction 2 register to 0, COL_ are

inputs, and ROW_ are outputs. When setting the bit to 1,

ROW_ become inputs and COL_ become outputs.

GPIO Global Configuration Register (0x40)

The GPIO Global Configuration register controls the main

settings for the GPIO ports. See Table 24. Bit D5 enables

interrupt generation for I2C timeouts. D4 is the main

enable/shutdown bit for the GPIOs. Bit D3 functions as a

software reset for the GPIO registers (0x31 to 0x5B). Bits

D[2:0] set the fade-in/out time for the LED drivers.

GPIO Debounce Configuration Register (0x42)

The GPIO Debounce Configuration Register sets the

amount of time a GPIO must be held in order for the

device to register a logic transition. See Table 25. The

GPIO debounce setting is independent of the key-switch

debounce setting. Five bits (D[4:0]) set 32 possible

debounce times from 9ms up to 40ms.

LED Constant-Current Setting Register (0x43)

The LED Constant-Current Setting register sets the global

constant-current amount. See Table 26. Bit D0 selects

the global current values between 10mA and 20mA.

This setting only applies to the LED driver-enabled pins,

COL7–COL4.

Common PWM Ratio Register (0x45)

The Common PWM Ratio register stores the common

constant-current output PWM duty cycle. See Table 27.

The values stored in this register translate over to a PWM

ratio in the same manner as the individual PWM ratio reg-

isters (0x50 to 0x53). Ports can use their own individual

PWM value or the common PWM value. Write to this reg-

ister to change the PWM ratio of several ports at once.

I2C Timeout Flag Register (0x48) (Read Only)

The I2C Timeout Flag register contains a single bit

(D0) that indicates if an I2C timeout has occurred. See

Table 28. Read this register to clear an I2C timeout-

initiated interrupt.

COL4–COL7 Individual PWM Ratio

Registers (0x50 to 0x53)

Each LED driver port has an individual PWM ratio register,

0x50 to 0x53. See Table 29. Use values 0x00 to 0xFE in

these registers to configure the number of cycles out of

256 the output sinks current (LED is on), from 0 cycles to

254 cycles. Use 0xFF to have an output continuously sink

current (always on). For applications requiring multiple

ports to have the same intensity, program a particular

port’s configuration register (0x54 to 0x57) to use the

Common PWM Ratio register (0x45). New PWM settings

take place at the beginning of a PWM cycle, to allow

changes from common intensity to individual intensity with

no interruption in the PWM cycle.

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

13Maxim Integrated

COL4–COL7 LED Configuration

Registers (0x54 to 0x57)

Registers 0x54 to 0x57 set individual configurations for

each port. See Table 30. D5 sets the port’s PWM setting

to either the common or individual PWM setting. Bits

D[4:2] enable and set the port’s individual blink period

from 0 to 4096ms. Bits D[1:0] set a port’s blink duty cycle.

Interrupt Mask 1 and 2 Registers (0x58, 0x59)

The Interrupt Mask 1 and 2 registers control which ports

trigger an interrupt for ROW7–ROW0 and COL7–COL0,

respectively. See Tables 31 and 32. Set the bit to 0 to

enable the interrupt. Set the bit to 1 to mask the interrupt.

If the port that has generated the interrupt is not masked,

the interrupt causes the INT signal to assert. A read of the

GPIO Values 1 and 2 registers (0x3A, 0x3B) is required

to deassert the INT pin. Note that transitions that occur

while the INT signal is asserted, but before the read of the

GPIO Values 1 and 2 registers, set the appropriate bit of

the GPIO Values 1 and 2 registers only, but has no effect

on the INT pin as it is already asserted. However, transi-

tions that occur when the I2C is active cannot be latched

into the GPIO Values 1 and 2 registers until after the read

has taken place. If there are transitions that cause the

INT signal to assert, during the time of an I2C read, they

cause the INT signal to reassert once the read transac-

tion has taken place. Note that the interrupt configura-

tions only apply when a port is configured as an input.

GPI Trigger Mode 1 and 2 Registers (0x5A, 0x5B)

The GPI Trigger Mode 1 and 2 registers control how ports

can trigger an interrupt for ROW7–ROW0 and COL7–

COL0, respectively. See Tables 33 and 34. Set the bit to

0 for rising-edge triggering. Set the bit to 1 for rising- and

falling-edge triggering.

The inputs are debounced (if enabled) by taking a snap-

shot of the port state when the transition occurs, and

another after the debounce time has elapsed—ensuring

that the state of the port is stable prior to triggering the

interrupt. After the debounce cycle, an interrupt is gener-

ated and the INT pin asserted if it is not masked for that

particular port. Regardless of whether or not the INT sig-

nal is masked, the GPIO Values 1 and 2 registers (0x3A,

0x3B) report the state of all input ports.

Sleep Mode

The device is put into sleep mode by clearing bit D7 in

the Configuration register, or after power-on reset (POR).

In sleep mode, the keyscan controller is disabled and the

device draws minimal current. No additional supply cur-

rent is drawn if no keys are pressed. All switch-matrix cur-

rent sources are turned off, and row outputs ROW7–ROW0

are low and column outputs COL7–COL0 become high.

The device is taken out of sleep mode and put into oper-

ating mode by setting bit D7 in the configuration register.

The keyscan controller FIFO buffers are cleared and key

monitoring starts. Note that rewriting the configuration

does not clear the FIFOs. The FIFOs are only cleared

when the device is changing state from sleep mode to

operating mode.

In sleep mode, the internal oscillator is disabled and

I2C timeout features are disabled. The GPO or LED

ports consume current even in sleep mode. The part

does not enter sleep mode if any of the GPIOs or LED

drivers are enabled.

LED Fade

Set the fade cycle time in the GPIO Global Configuration

See Table 24. Fade in increases an LED’s PWM intensity

in 16 even steps, from zero to its stored value. Fade out

decreases an LED’s PWM intensity in 16 even steps from

its current value to zero. Fading occurs automatically in

any of the following scenarios:

• Change the common PWM register value from any

value to zero to cause all ports using the common

PWM register settings to fade out. No ports using

individual PWM settings are affected.

• ChangethecommonPWMregistervaluetoanyvalue

from zero to cause all ports using the common PWM

PWM settings are affected.

• Takethepartoutofsleepmodetocauseallportsto

fade in. Changing an individual PWM intensity dur-

ing fade in automatically cancels that port’s fade and

immediately outputs at its newly programmed intensity.

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

14Maxim Integrated

• Putthepartintosleepmodetocauseallportstofade

out. Changing an individual PWM intensity during

fade out automatically cancels that port’s fade and

immediately turns off.

LED PWM

Each port has an individual PWM ratio register. The value

stored in this register configures the number of cycles

out of 255 that the output is sinking current (LED is on).

Setting a value of 0xFF in an individual intensity register

sets the output to continuously sink current (always on).

Conversely, setting a value of 0x00 in an individual inten-

sity register sets the output in a high-impedance state

(always off).

For applications requiring multiple ports to have the

same intensity, the common PWM ratio intensity setting

can be used in lieu of the individual intensity setting. To

use the common intensity setting, program bit D5 of the

corresponding port’s configuration register to logic-high.

Setting a port to use the common PWM ratio setting

copies the value of the common intensity register into

the individual intensity register at the beginning of each

PWM cycle. This allows an output port to be seamlessly

changed from common intensity to individual intensity

with no interruption in the PWM cycle.

Outputs are configured to sink a constant current of either

10mA or 20mA during the period of time when the output

is on. The setting in the individual GPIO constant-current

setting register (0x43) controls the value of the current.

LED Blink

Each LED driver-supported port has its own blink-control

settings through registers 0x54 to 0x57. See Table 30.

The blink period ranges from 0 (blink disabled) to 4.096s.

Settable blink duty cycles range from 6.25% to 50%. All

blink periods start at the same PWM cycle for synchro-

nized blinking between multiple ports.

Each port has its own counter to generate blink timing.

The blink counter can be programmed to cause the out-

put to gate off and on at a programmable rate. The blink

period can be set to 256ms, 512ms, 1.024s, 2.048s, or

4.096s using D[4:2] of the port’s individual configuration

one blink cycle is set to 50%, 25%, 12.5%, or 6.25% by

D[1:0] of the individual configuration register.

Interrupts

Three possible sources generate INT: key-switch FIFO

level/debounce cycle settings, I2C timeout, or GPIOs

configured as inputs (registers 0x03, 0x48, 0x5A, and

0x5B). Read the respective data/status registers for each

type of interrupt to clear INT. If multiple sources generate

the interrupt, all the related status registers must be read

to clear INT.

Serial Interface

Figure 1 shows the two-wire serial interface timing details.

Figure 1. Two-Wire Serial Interface Timing Details

SDA

SCL

tHD, STA

tLOW

tHIGH

tRtF

tSU, DAT tSU, STA

tSU, STO

tBUF

tHD, STA

tHD, DAT

START

CONDITION

STOP

CONDITION

START

CONDITION

REPEATED

START CONDITION

tF, TX

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

15Maxim Integrated

Figure 2. START and STOP Conditions

Serial Addressing

The device operates as a slave that sends and receives

data through an I2C-compatible two-wire interface. The

interface uses a serial-data line (SDA) and a serial-

clock line (SCL) to achieve bidirectional communication

between master(s) and slave(s). A master (typically a

microcontroller) initiates all data transfers to and from the

device and generates the SCL clock that synchronizes

the data transfer.

The device’s SDA line operates as both an input and an

open-drain output. A pullup resistor, typically 4.7kω, is

required on SDA. The device’s SCL line operates only as

an input. A pullup resistor is required on SCL if there are

multiple masters on the two-wire interface, or if the master

in a single-master system has an open-drain SCL output.

Each transmission consists of a START (S) condition

(Figure 2) sent by a master, followed by the device’s 7-bit

slave address plus R/W bit, a register address byte, one

or more data bytes, and finally, a STOP (P) condition.

START and STOP Conditions

Both SCL and SDA remain high when the interface is not

busy. A master signals the beginning of a transmission

with a START condition by transitioning SDA from high

to low while SCL is high. When the master has finished

communicating with the slave, it issues a STOP condition

by transitioning SDA from low to high while SCL is high.

The bus is then free for another transmission.

Bit Transfer

One data bit is transferred during each clock pulse

(Figure 3). The data on SDA must remain stable while

SCL is high.

Acknowledge

The acknowledge bit is a clocked 9th bit (Figure 4), which

the recipient uses to handshake receipt of each byte of

data. Thus, each byte transferred effectively requires 9

bits. The master generates the 9th clock pulse, and the

recipient pulls down SDA during the acknowledge clock

pulse; therefore, the SDA line is stable low during the

high period of the clock pulse. When the master is trans-

mitting to the device, the device generates the acknowl-

edge bit because the device is the recipient. When the

device is transmitting to the master, the master generates

the acknowledge bit because the master is the recipient.

Figure 3. Bit Transfer

SDA

SCL

START

CONDITION

STOP

CONDITION

S P

SDA

SCL

DATA LINE STABLE;

DATA VALID

CHANGE OF DATA

ALLOWED

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

16Maxim Integrated

Slave Addresses

The device has two 7-bit long slave addresses. The bit

following a 7-bit slave address is the R/W bit, which is

low for a write command and high for a read command.

The first 4 bits (MSBs) of the device slave addresses

are always 0111. Slave address bits A[3:1] correspond,

by the matrix in Table 3, to the states of the device

address input pin AD0, and A0 corresponds to the

R/W bit (Figure 5). The AD0 input can be connected

to any of four signals: GND, VCC, SDA, or SCL, giv-

ing four possible slave-address pairs, allowing up to

four devices to share the same bus. Because SDA and

SCL are dynamic signals, care must be taken to ensure

that AD0 transitions no sooner than the signals on

SDA and SCL.

The device monitors the bus continuously, waiting for a

START condition, followed by its slave address. When

the device recognizes its slave address, it acknowledges

and is then ready for continued communication.

Bus Timeout

The device features a 20ms (min) bus timeout on the

two-wire serial interface, largely to prevent the device

from holding the SDA I/O low during a read transac-

tion should the SCL lock up for any reason before a

serial transaction is completed. Bus timeout operates by

causing the device to internally terminate a serial trans-

action, either read or write, if the time between adjacent

edges on SCL exceeds 20ms. After a bus timeout, the

device waits for a valid START condition before respond-

ing to a consecutive transmission. This feature can be

enabled or disabled under user control by writing to the

configuration register.

Message Format for Writing

the Keyscan Controller

A write to the device comprises the transmission of the slave

address with the R/W bit set to zero, followed by at least one

byte of information. The first byte of information is the com-

mand byte. The command byte determines which register

of the device is to be written by the next byte, if received.

If a STOP condition is detected after the command byte

is received, the device takes no further action (Figure 6)

beyond storing the command byte.

Any bytes received after the command byte are data bytes.

The first data byte goes into the internal register of the

device selected by the command byte (Figure 7).

If multiple data bytes are transmitted before a STOP condi-

tion is detected, these bytes are generally stored in sub-

sequent internal registers of the device, because the com-

mand-byte address generally autoincrements (Table 4).

Figure 4. Acknowledge

Figure 5. Slave Address

Table 3. Two-Wire Interface Address Map

AD0

DEVICE ADDRESS

A7 A6 A5 A4 A3 A2 A1 A0

GND

0111

0 0

0R/W

VCC 0 1

SDA 1 0

SCL 1 1

SCL

SDA BY

TRANSMITTER

CLOCK PULSE FOR

ACKNOWLEDGE

START

CONDITION

SDA BY

RECEIVER

1 2 8 9

SDA

SCL

01 1A3A2A11

MSB LSB

ACKR/W

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

17Maxim Integrated

Message Format for Reading

the Keyscan Controller

The device is read using the internally stored command

byte as an address pointer, the same way the stored

command byte is used as an address pointer for a

write. The pointer generally autoincrements after each

data byte is read using the same rules as for a write

(Table 4). Thus, a read is initiated by first configuring the

device’s command byte by performing a write (Figure 6).

The master can now read N consecutive bytes from the

device, with the first data byte being read from the reg-

ister addressed by the initialized command byte. When

performing read-after-write verification, remember to

reset the command byte’s address because the stored

command byte address is generally autoincremented

after the write (Figure 8, Table 4).

Figure 7. Command and Single Data Byte Received

Figure 6. Command Byte Received

Figure 8. N Data Bytes Received

Table 4. Autoincrement Rules

FUNCTION

ADDRESS

CODE (hex)

AUTOINCREMENT

ADDRESS (hex)

Keys FIFO 0x00 0x00

Autosleep 0x06 0x00

All other key

switches 0x01 to 0x05 Addr + 0x01

All other GPIOs 0x30 to 0x5B Addr + 0x01

SAAP0SLAVE ADDRESS COMMAND BYTE

D7 D6 D5 D4 D3 D2 D1 D0

COMMAND BYTE IS STORED ON RECEIPT OF

ACKNOWLEDGE CONDITION

ACKNOWLEDGE FROM MAX7370

R/W

P0SLAVE ADDRESS COMMAND BYTE DATA BYTE

1 BYTE

AUTOINCREMENT

COMMAND BYTE ADDRESS

D7 D6 D5 D4 D3 D2 D1 D0 D1 D0D3 D2D5 D4D7 D6

ACKNOWLEDGE FROM MAX7370 ACKNOWLEDGE FROM MAX7370

ACKNOWLEDGE FROM MAX7370

R/W

P0SLAVE ADDRESS COMMAND BYTE DATA BYTE

N BYTES

AUTOINCREMENT

COMMAND BYTE ADDRESS

D7 D6 D5 D4 D3 D2 D1 D0 D1 D0D3 D2D5 D4D7 D6

ACKNOWLEDGE FROM MAX7370 ACKNOWLEDGE FROM MAX7370

ACKNOWLEDGE FROM MAX7370

R/W

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

18Maxim Integrated

Operation with Multiple Masters

When the device is operated on a two-wire interface with

multiple masters, a master reading the device uses a

repeated start between the write that sets the device’s

address pointer, and the read(s) that takes the data

from the location(s). This is because it is possible for

master 2 to take over the bus after master 1 has set

up the device’s address pointer but before master 1

has read the data. If master 2 subsequently resets the

device’s address pointer, master 1’s read can be from an

unexpected location.

Command Address Autoincrementing

Address autoincrementing allows the device to be

configured with fewer transmissions by minimizing the

number of times the command address needs to be

sent. The command address stored in the device gener-

ally increments after each data byte is written or read

(Table 4). Autoincrement only functions when doing a

multiburst read or write.

Applications Information

Reset from I2C

After a catastrophic event such as ESD discharge or

microcontroller reset, use bit D7 of the configuration reg-

ister (0x01) as a software reset for the key switches. Use

bit D4 of the GPIO global configuration register (0x40) as

a software reset for the GPIOs.

Ghost-Key Elimination

Ghost keys are a phenomenon inherent with key-switch

matrices. When three switches located at the corners

of a matrix rectangle are pressed simultaneously, the

switch that is located at the last corner of the rectangle

(the ghost key) also appears to be pressed. This occurs

because the potentials at the two sides of the ghost-key

switch are identical due to the other three connections—

the switch is electrically shorted by the combination of

the other three switches (Figure 9). Because the key

appears to be pressed electrically, it is impossible to

detect which of the four keys is the ghost key.

The device employs a proprietary scheme that detects

any three-key combination that generates a fourth ghost

key, and does not report the third key that causes a

ghost-key event. This means that although ghost keys

are never reported, many combinations of three keys

are effectively ignored when pressed at the same time.

Applications requiring three-key combinations (such as

<Ctrl><Alt><Del>) must ensure that the three keys are

not wired in positions that define the vertices of a rect-

angle (Figure 10). There is no limit on the number of keys

that can be pressed simultaneously as long as the keys

do not generate ghost-key events and the FIFO is not full.

Low-EMI Operation

The device uses two techniques to minimize EMI radiat-

ing from the key-switch wiring. First, the voltage across

the switch matrix never exceeds 0.5V if not in sleep

mode, independent of supply voltage VCC. This reduces

the voltage swing at any node when a switch is pressed

to 0.5V (max). Second, the keys are not dynamically

scanned, which would cause the key-switch wiring to

continuously radiate interference. Instead, the keys are

monitored for current draw (only occurs when pressed),

and debounce circuitry only operates when one or more

keys are actually pressed.

Figure 9. Ghost-Key Phenomenon Figure 10. Valid Three-Key Combinations

REGULAR KEYPRESS

EVENT

GHOST-KEY

EVENT

KEY-SWITCH MATRIX

KEY-SWITCH MATRIX KEY-SWITCH MATRIX

EXAMPLES OF VALID THREE-KEY COMBINATIONS

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

19Maxim Integrated

Switch On-Resistance

The device is designed to be insensitive to resistance,

either in the key switches, or the switch routing to and

from the appropriate COL_ and ROW_ up to 5kI (max).

These controllers are therefore compatible with low-cost

membrane and conductive carbon switches.

Hot Insertion

The INT, SCL, and AD0 inputs and SDA remain high

impedance with up to 5.5V asserted on them when the

device powers down (VCC = 0V). I/O ports remain high

impedance with up to 5.5V asserted on them when not

powered. Use the device in hot-swap applications.

Staggered PWM

The LED’s on-time in each PWM cycle is phase delayed by

45N into four evenly spaced start positions. Optimize phas-

ing, when using fewer than four ports as constant-current

outputs, by allocating the ports with the most appropriate

start positions. For example, if using two constant-current

outputs, choose COL4 and COL6 because their PWM

start positions are evenly spaced. In general, choose

the ports that spread the current demand from the ports’

load supply.

Power-Supply Considerations

The device operates with a 1.62V to 3.6V power-supply

voltage. Bypass the power supply (VCC) to GND with a

0.1µF or higher ceramic capacitor as close as possible

to the device. Bypass the logic power supply (VLA) to

GND with a 0.1µF or higher ceramic capacitor as close

as possible to the device.

ESD Protection

All the device pins meet the ±2.5kV Human Body Model

ESD tolerances. Key-switch inputs and GPIOs meet IEC

61000-4-2 ESD protection. The IEC test stresses consist

of 10 consecutive ESD discharges per polarity at the

maximum specified level and below (per IEC 61000-4-2).

Test criteria include:

• ThepowereddevicedoesnotlatchupduringtheESD

discharge event.

• The device subsequently passes the final test used

for prescreening.

Tables 5 and 6 are taken from the IEC 61000-4-2:

Edition 1.1 1999-05: Electromagnetic compatibility (EMC)

Testing and measurement techniques—Electrostatic dis-

charge immunity test.

Table 5. ESD Test Levels

Table 6. ESD Waveform Parameters

X = Open level. The level has to be specified in the dedicated

equipment specification. If higher voltages than those shown

are specified, special test equipment might be needed.

1A—CONTACT DISCHARGE 1B—AIR DISCHARGE

LEVEL TEST VOLTAGE

(kV) LEVEL TEST

VOLTAGE (kV)

1 2 1 2

2 4 2 4

3 6 3 8

4 8 4 15

X Special X Special

LEVEL

INDICATED

VOLTAGE

(kV)

FIRST PEAK

OF CURRENT

DISCHARGE Q10%

(A)

RISE TIME (tr) WITH

DISCHARGE SWITCH

(ns)

CURRENT

(Q30%) AT 30ns

(A)

CURRENT (Q30%)

AT 60ns

(A)

1 2 7.5 0.7 to 1 4 2

2 4 15 0.7 to 1 8 4

3 6 22.5 0.7 to 1 12 6

4 8 30 0.7 to 1 16 8

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

20Maxim Integrated

Table 7. Keys FIFO Register Format (0x00)

SPECIAL FUNCTION KEYS FIFO REGISTER DATA

D7 D6 D5 D4 D3 D2 D1 D0

The key number indicated by

D[5:0] is a key event. D7 is

always for a keypress of key 62

and key 63. When D7 is 0, the

key read is the last data in the

FIFO. When D7 is 1, there is

more data in the FIFO. When D6

is 1, key data read from the FIFO

is a key release. When D6 is 0,

key data read from the FIFO is a

keypress.

FIFO not-

empty flag

Key-

release

flag

Key number/key event

FIFO is empty. 00111111

FIFO is overflow. Continue to

read data in the FIFO. 01111111

Key 63 is pressed. Read one

more time to determine whether

there is more data in the FIFO.

10111111

Key 63 is released. Read one

more time to determine whether

there is more data in the FIFO.

11111111

Key repeat. Indicates the last

data in the FIFO. 00111110

Key repeat. Indicates more data

in the FIFO. 01111110

Key 62 is pressed. Read one

more time to determine whether

there is more data in the FIFO.

10111110

Key 62 is released. Read one

more time to determine whether

there is more data in the FIFO.

11111110

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

21Maxim Integrated

Table 8. Configuration Register (0x01)

X = Don’t care.

BIT DESCRIPTION VALUE FUNCTION DEFAULT

VALUE

D7 Sleep

(when 0x40

D4 = 1)

Key-switch operating mode. Key switches always remain active

when constant-current PWM is enabled (bit 4 of register 0x40 is

high), regardless of autosleep, autowake, or an I2C write to this bit.

(when 0x40

D4 = 0)

Key-switch sleep

mode. The entire

chip is shut down.

When constant-current PWM is disabled

(bit 4 of register 0x40 is low), I2C write,

autosleep, and autowake all can change

this bit. This bit can be read back by I2C

any time for current status.

(when 0x40

D4 = 0)

Key-switch operating

mode.

D6 Reserved 0 — 0

D5 Interrupt

0INT cleared when the FIFO is empty.

INT cleared after host read. In this mode, I2C should read the

FIFO until interrupt condition is removed or further INT could be

lost.

D4 Reserved 0 — 0

D3 Key-release

enable

0 Disable key releases. 1

1 Enable key releases.

D2 Reserved 0 — 0

D1 Autowake

enable

0 Disable keypress wakeup. 1

1 Enable keypress wakeup.

D0 Timeout

disable

0 I2C timeout enabled. 1

1 I2C timeout disabled.

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

22Maxim Integrated

Table 9. Key-Switch Debounce Register (0x02)

Table 10. Key-Switch Interrupt Register (0x03)

X = Don’t care.

D7 D6 D5 D4 D3 D2 D1 D0

DEBOUNCE TIME RELEASE DEBOUNCE TIME PRESS DEBOUNCE TIME

2ms

0 0 0 0

4ms 0 0 0 1

6ms 0 0 1 0

⋮

28ms

1 1 0 1

30ms 1 1 1 0

32ms 1 1 1 1

2ms 0 0 0 0

X4ms 0 0 0 1

6ms 0 0 1 0

⋮

28ms 1 1 0 1

X30ms 1 1 1 0

32ms 1 1 1 1

Power-on default (32ms) 1 1 1 1 1 1 1 1

D7 D6 D5 D4 D3 D2 D1 D0

FIFO-BASED INT TIME-BASED INT

Power-up default setting

All INT disabled 0 0 0 0 0 0 0 0

Time-based INT disabled

0 0 0 0 0

INT asserts every debounce cycle 0 0 0 0 1

INT asserts every 2 debounce cycles 0 0 0 1 0

⋮

INT asserts every 29 debounce cycles

1 1 1 0 1

INT asserts every 30 debounce cycles 1 1 1 1 0

INT asserts every 31 debounce cycles 1 1 1 1 1

FIFO-based INT disabled 0 0 0

INT asserts when the FIFO has 2 key events 0 0 1

INT asserts when the FIFO has 4 key events 0 1 0

⋮

INT asserts when the FIFO has 10 key events 1 0 1

INT asserts when the FIFO has 12 key events 1 1 0

INT asserts when the FIFO has 14 key events 1 1 1

Both time-based and FIFO-based interrupts active Not all zero Not all zero

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

23Maxim Integrated

Table 11. Key-Switch Autorepeat Register (0x05)

Table 12. Autosleep Register (0x06)

X = Don’t care.

D7 D6 D5 D4 D3 D2 D1 D0

ENABLE AUTOREPEAT RATE AUTOREPEAT DELAY

Autorepeat is disabled 0 XXXXXXX

Autorepeat is enabled 1Autorepeat rate Autorepeat delay

Autorepeat delay is 8 debounce cycles 1

0000

Autorepeat delay is 16 debounce cycles 1 0001

Autorepeat delay is 24 debounce cycles 1 0010

⋮

Autorepeat delay is 112 debounce cycles 1

1101

Autorepeat delay is 120 debounce cycles 1 1110

Autorepeat delay is 128 debounce cycles 1 1111

Autorepeat frequency is 4 debounce cycles 1 0 0 0

Autorepeat frequency is 8 debounce cycles 1 0 0 1

Autorepeat frequency is 12 debounce

cycles 1 0 1 0

⋮

Autorepeat frequency is 24 debounce

cycles 1 1 0 1

Autorepeat frequency is 28 debounce

cycles 1 1 1 0

Autorepeat frequency is 32 debounce

cycles 1 1 1 1

Power-on default setting 0 0000000

AUTOSLEEP (ms)

RESERVED AUTOSHUTDOWN TIME

D7 D6 D5 D4 D3 D2 D1 D0

Autosleep disabled 00000000

8192 0 0 0 0 0 0 0 1

4096 0 0 0 0 0 0 1 0

2048 0 0 0 0 0 0 1 1

1024 0 0 0 0 0 1 0 0

512 00000101

256 00000110

256 00000111

Power-up default settings 00000111

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

24Maxim Integrated

Table 13. Key-Switch Array Size Register (0x30)

Table 14. LED Driver Enable Register (0x31)

X = Don’t care.

D7 D6 D5 D4 D3 D2 D1 D0

ROWS COLUMNS

No rows are key switches 0000

ROW0 is a key switch 0001

ROW0 to ROW1 are key switches 0010

ROW0 to ROW2 are key switches 0011

ROW0 to ROW3 are key switches 0100

ROW0 to ROW4 are key switches 0101

ROW0 to ROW5 are key switches 0110

ROW0 to ROW6 are key switches 0111

ROW0 to ROW7 are key switches 1 X X X

No columns are key switches

0000

COL0 is a key switch 0001

COL0 to COL1 are key switches 0010

COL0 to COL2 are key switches 0011

COL0 to COL3 are key switches 0100

COL0 to COL4 are key switches 0101

COL0 to COL5 are key switches 0110

COL0 to COL6 are key switches 0111

COL0 to COL7 are key switches 1 X X X

Power-up default setting 11111111

D[7:4] Reserved 0000 — 0000

D3 COL7 0GPIO function 0

1LED driver enable

D2 COL6 0GPIO function 0

1LED driver enable

D1 COL5 0GPIO function 0

1LED driver enable

D0 COL4 0GPIO function 0

1LED driver enable

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

25Maxim Integrated

Table 15. GPIO Direction 1 Register (0x34)

Table 16. GPIO Direction 2 Register (0x35)

D7 ROW7 0 Set as input pin 0

1 Set as output pin

D6 ROW6 0 Set as input pin 0

1 Set as output pin

D5 ROW5 0 Set as input pin 0

1 Set as output pin

D4 ROW4 0 Set as input pin 0

1 Set as output pin

D3 ROW3 0 Set as input pin 0

1 Set as output pin

D2 ROW2 0 Set as input pin 0

1 Set as output pin

D1 ROW1 0 Set as input pin 0

1 Set as output pin

D0 ROW0 0 Set as input pin 0

1 Set as output pin

D7 COL7 0 Set as input pin 0

1 Set as output pin

D6 COL6 0 Set as input pin 0

1 Set as output pin

D5 COL5 0 Set as input pin 0

1 Set as output pin

D4 COL4 0 Set as input pin 0

1 Set as output pin

D3 COL3 0 Set as input pin 0

1 Set as output pin

D2 COL2 0 Set as input pin 0

1 Set as output pin

D1 COL1 0 Set as input pin 0

1 Set as output pin

D0 COL0 0 Set as input pin 0

1 Set as output pin

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

26Maxim Integrated

Table 17. GPO Output Mode 1 Register (0x36)

Table 18. GPO Output Mode 2 Register (0x37)

Note: When programmed as GPO, COL7–COL4 are always open drain and bits D[7:4] are not writable.

D7 ROW7 0 Port is an open-drain output 1

1 Port is a push-pull output

D6 ROW6 0 Port is an open-drain output 1

1 Port is a push-pull output

D5 ROW5 0 Port is an open-drain output 1

1 Port is a push-pull output

D4 ROW4 0 Port is an open-drain output 1

1 Port is a push-pull output

D3 ROW3 0 Port is an open-drain output 1

1 Port is a push-pull output

D2 ROW2 0 Port is an open-drain output 1

1 Port is a push-pull output

D1 ROW1 0 Port is an open-drain output 1

1 Port is a push-pull output

D0 ROW0 0 Port is an open-drain output 1

1 Port is a push-pull output

D7 COL7 0 Port is an open-drain output 0

D6 COL6 0 Port is an open-drain output 0

D5 COL5 0 Port is an open-drain output 0

D4 COL4 0 Port is an open-drain output 0

D3 COL3 0 Port is an open-drain output 1

1 Port is a push-pull output

D2 COL2 0 Port is an open-drain output 1

1 Port is a push-pull output

D1 COL1 0 Port is an open-drain output 1

1 Port is a push-pull output

D0 COL0 0 Port is an open-drain output 1

1 Port is a push-pull output

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

27Maxim Integrated

Table 19. GPIO Supply Voltage 1 Register (0x38)

Table 20. GPIO Supply Voltage 2 Register (0x39)

D7 ROW7 0 ROW7 supplied by VCC 0

1 ROW7 supplied by VLA

D6 ROW6 0 ROW6 supplied by VCC 0

1 ROW6 supplied by VLA

D5 ROW5 0 ROW5 supplied by VCC 0

1 ROW5 supplied by VLA

D4 ROW4 0 ROW4 supplied by VCC 0

1 ROW4 supplied by VLA

D3 ROW3 0 ROW3 supplied by VCC 0

1 ROW3 supplied by VLA

D2 ROW2 0 ROW2 supplied by VCC 0

1 ROW2 supplied by VLA

D1 ROW1 0 ROW1 supplied by VCC 0

1 ROW1 supplied by VLA

D0 ROW0 0 ROW0 supplied by VCC 0

1 ROW0 supplied by VLA

D7 COL7 0 COL7 supplied by VCC 0

1 COL7 supplied by VLA

D6 COL6 0 COL6 supplied by VCC 0

1 COL6 supplied by VLA

D5 COL5 0 COL5 supplied by VCC 0

1 COL5 supplied by VLA

D4 COL4 0 COL4 supplied by VCC 0

1 COL4 supplied by VLA

D3 COL3 0 COL3 supplied by VCC 0

1 COL3 supplied by VLA

D2 COL2 0 COL2 supplied by VCC 0

1 COL2 supplied by VLA

D1 COL1 0 COL1 supplied by VCC 0

1 COL1 supplied by VLA

D0 COL0 0 COL0 supplied by VCC 0

1 COL0 supplied by VLA

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

28Maxim Integrated

Table 21. GPIO Values 1 Register (0x3A)

Table 22. GPIO Values 2 Register (0x3B)

*Open-drain output, pullup resistor required.

D7 ROW7 0 Clear ROW7 low 1

1 Set ROW7 high

D6 ROW6 0 Clear ROW6 low 1

1 Set ROW6 high

D5 ROW5 0 Clear ROW5 low 1

1 Set ROW5 high

D4 ROW4 0 Clear ROW4 low 1

1 Set ROW4 high

D3 ROW3 0 Clear ROW3 low 1

1 Set ROW3 high

D2 ROW2 0 Clear ROW2 low 1

1 Set ROW2 high

D1 ROW1 0 Clear ROW1 low 1

1 Set ROW1 high

D0 ROW0 0 Clear ROW0 low 1

1 Set ROW0 high

D7 COL7 0 Clear COL7 low 1

1 Set COL7 high*

D6 COL6 0 Clear COL6 low 1

1 Set COL6 high*

D5 COL5 0 Clear COL5 low 1

1 Set COL5 high*

D4 COL4 0 Clear COL4 low 1

1 Set COL4 high*

D3 COL3 0 Clear COL3 low 1

1 Set COL3 high

D2 COL2 0 Clear COL2 low 1

1 Set COL2 high

D1 COL1 0 Clear COL1 low 1

1 Set COL1 high

D0 COL0 0 Clear COL0 low 1

1 Set COL0 high

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

29Maxim Integrated

Table 23. GPIO Level-Shifter Enable Register (0x3C)

D7 COL7

0Level shifting disabled

Level shift between COL7 and ROW7 enabled;

direction controlled by GPIO direction 2 register

(0x35)

D6 COL6 0

Level shifting disabled

Level shift between COL6 and ROW6 enabled;

direction controlled by GPIO direction 2 register

(0x35)

D5 COL5

0Level shifting disabled

Level shift between COL5 and ROW5 enabled;

direction controlled by GPIO direction 2 register

(0x35)

D4 COL4

0Level shifting disabled

Level shift between COL4 and ROW4 enabled;

direction controlled by GPIO direction 2 register

(0x35)

D3 COL3

0Level shifting disabled

Level shift between COL3 and ROW3 enabled;

direction controlled by GPIO direction 2 register

(0x35)

D2 COL2

0Level shifting disabled

Level shift between COL2 and ROW2 enabled;

direction controlled by GPIO direction 2 register

(0x35)

D1 COL1

0Level shifting disabled

Level shift between COL1 and ROW1 enabled;

direction controlled by GPIO direction 2 register

(0x35)

D0 COL0

0Level shifting disabled

Level shift between COL0 and ROW0 enabled;

direction controlled by GPIO direction 2 register

(0x35)

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

30Maxim Integrated

Table 24. GPIO Global Configuration Register (0x40)

Table 25. GPIO Debounce Configuration Register (0x42)

D7 D6 D5 D4 D3 D2 D1 D0

RESERVED DEBOUNCE TIME

Power-up default setting

Debounce time is 9ms 00000000

Debounce time is 10ms 0 0 0 0 0 0 0 1

Debounce time is 11ms 0 0 0 0 0 0 1 0

Debounce time is 12ms 0 0 0 0 0 0 1 1

⋮

Debounce time is 37ms 0 0 0 1 1 1 0 0

Debounce time is 38ms 0 0 0 1 1 1 0 1

Debounce time is 39ms 0 0 0 1 1 1 1 0

Debounce time is 40ms 0 0 0 1 1 1 1 1

D[7:6] Reserved 0 — 00

D5 I2C timeout

interrupt enable

0 Disabled

INT is asserted when I2C bus times out. INT is

deasserted when a read is performed on the I2C

timeout flag register (0x48).

D4 GPIO enable

PWM, constant-current circuits, and GPIs are

shut down. GPO values depend on their setting.

cannot be changed. The entire part is shut down

if the key switches are in sleep mode

(D7 of register 0x01). 0

Normal GPIO operation. PWM, constant-current

circuits, and GPIOs are enabled regardless of

key-switch sleep-mode state (see Table 8).

D3 GPIO reset

0 Normal operation

Return all GPIO registers (registers 0x31 to 0x5B)

to their POR value. This bit is momentary and

resets itself to 0 after the write cycle.

D[2:0] Fade-in/out time

000 No fading

000

XXX

PWM intensity ramps up (down) between the

common PWM value and 0% duty cycle in 16

steps over the following time period:

D[2:0] = 001 = 256ms

D[2:0] = 010 = 512ms

D[2:0] = 011 = 1024ms

D[2:0] = 100 = 2048ms

D[2:0] = 101 = 4096ms

D[2:0] = 110/111 = Undefined

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

31Maxim Integrated

Table 26. LED Constant-Current Setting Register (0x43)

Table 27. Common PWM Register (0x45)

Table 28. I2C Timeout Flag Register (0x48) (Read Only)

D[7:6] Reserved 11 Set always as 11 11

D[5:1] Reserved 00000 — 00000

D0 Constant-current

setting

0 Constant current is 20mA 0

1 Constant current is 10mA

D7 D6 D5 D4 D3 D2 D1 D0

COMMON PWM

Power-up default setting

Common PWM ratio is 0/256 00000000

Common PWM ratio is 1/256 0 0 0 0 0 0 0 1

Common PWM ratio is 2/256 0 0 0 0 0 0 1 0

Common PWM ratio is 3/256 0 0 0 0 0 0 1 1

⋮

Common PWM ratio is 252/256 1 1 1 1 1 1 0 0

Common PWM ratio is 253/256 1 1 1 1 1 1 0 1

Common PWM ratio is 254/256 1 1 1 1 1 1 1 0

Common PWM ratio is 256/256 (100% duty cycle) 1 1 1 1 1 1 1 1

D[7:1] Reserved 0000000 — 0000000

D0 I2C timeout flag

0No I2C timeout has occurred since last read or

POR.

I2C timeout has occurred since last read or POR.

This bit is reset to zero when a read is performed

on this register. I2C timeouts must be enabled for

this function to work (see Table 8).

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

32Maxim Integrated

Table 29. COL4–COL7 Individual PWM Ratio Registers (0x50 to 0x53)

Table 30. COL4–COL7 LED Configuration Registers (0x54 to 0x57)

D7 D6 D5 D4 D3 D2 D1 D0

PORT PWM

Power-up default setting

PORT PWM ratio is 0/256 00000000

PORT PWM ratio is 1/256 0 0 0 0 0 0 0 1

PORT PWM ratio is 2/256 0 0 0 0 0 0 1 0

PORT PWM ratio is 3/256 0 0 0 0 0 0 1 1

⋮

PORT PWM ratio is 252/256 1 1 1 1 1 1 0 0

PORT PWM ratio is 253/256 1 1 1 1 1 1 0 1

PORT PWM ratio is 254/256 1 1 1 1 1 1 1 0

PORT PWM ratio is 256/256 (100% duty cycle) 1 1 1 1 1 1 1 1

D[7:6] Don’t care 00 — 00

D5 Common PWM

0Port uses individual PWM intensity register to set

the PWM ratio 0

1Port uses common PWM intensity register to set

the PWM ratio

D[4:2] Blink period

000 Port does not blink

000

001 Port blink period is 256ms

010 Port blink period is 512ms

011 Port blink period is 1024ms

100 Port blink period is 2048ms

101 Port blink period is 4096ms

110/111 Undefined

D[1:0] Blink-on time

00 LED is on for 50% of the blink period

01 LED is on for 25% of the blink period

10 LED is on for 12.5% of the blink period

11 LED is on for 6.25% of the blink period

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

33Maxim Integrated

Table 31. Interrupt Mask 1 Register (0x58)

Table 32. Interrupt Mask 2 Register (0x59)

D7 ROW7 0 Interrupt is not masked 1

1 Interrupt is masked

D6 ROW6 0 Interrupt is not masked 1

1 Interrupt is masked

D5 ROW5 0 Interrupt is not masked 1

1 Interrupt is masked

D4 ROW4 0 Interrupt is not masked 1

1 Interrupt is masked

D3 ROW3 0 Interrupt is not masked 1

1 Interrupt is masked

D2 ROW2 0 Interrupt is not masked 1

1 Interrupt is masked

D1 ROW1 0 Interrupt is not masked 1

1 Interrupt is masked

D0 ROW0 0 Interrupt is not masked 1

1 Interrupt is masked

D7 COL7 0 Interrupt is not masked 1

1 Interrupt is masked

D6 COL6 0 Interrupt is not masked 1

1 Interrupt is masked

D5 COL5 0 Interrupt is not masked 1

1 Interrupt is masked

D4 COL4 0 Interrupt is not masked 1

1 Interrupt is masked

D3 COL3 0 Interrupt is not masked 1

1 Interrupt is masked

D2 COL2 0 Interrupt is not masked 1

1 Interrupt is masked

D1 COL1 0 Interrupt is not masked 1

1 Interrupt is masked

D0 COL0 0 Interrupt is not masked 1

1 Interrupt is masked

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

34Maxim Integrated

Table 33. GPI Trigger Mode 1 Register (0x5A)

Table 34. GPI Trigger Mode 2 Register (0x5B)

D7 ROW7 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D6 ROW6 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D5 ROW5 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D4 ROW4 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D3 ROW3 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D2 ROW2 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D1 ROW1 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D0 ROW0 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D7 COL7 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D6 COL6 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D5 COL5 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D4 COL4 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D3 COL3 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D2 COL2 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D1 COL1 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

D0 COL0 0 Rising-edge-triggered interrupts 0

1 Rising- and falling-edge-triggered interrupts

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

35Maxim Integrated

Typical Application Circuit

KEY 7 KEY 15 KEY 23 KEY 31

KEY 6 KEY 14 KEY 22 KEY 30

KEY 5 KEY 13 KEY 21 KEY 29

KEY 4 KEY 12 KEY 20 KEY 28

KEY 3 KEY 11 KEY 19 KEY 27

KEY 2 KEY 10 KEY 18 KEY 26

KEY 1 KEY 9 KEY 17 KEY 25

KEY 0 KEY 8 KEY 16 KEY 24

I/O

COL5

COL4

COL3

COL2

COL1

COL0

ROW7

ROW6

ROW5

ROW4

ROW3

ROW2

ROW1

ROW0

COL6

COL7

+5V

+1.8V

VCC

+2.6V

VLA

+3.3V

VCC

SDA

GND

SCL

µC

INT

SDA

SCL

INT

GND

AD0

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

36Maxim Integrated

Ordering Information

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed. pad.

**Future product—contact factory for availability.

Chip Information

PROCESS: BiCMOS

Wafer-Level Packaging (WLP)

Applications Information

For the latest application details on WLP construction,

dimensions, tape-carrier information, PCB techniques,

bump-pad layout, and recommended reflow tempera-

ture profile, as well as the latest information on reli-

ability testing results, refer to Application Note 1891:

Wafer-Level Packaging (WLP) and Its Applications,

available at www.maximintegrated.com.

Package Information

For the latest package outline information and land patterns (foot-

prints), go to www.maximintegrated.com/packages. Note that a

“+”, “#”, or “-” in the package code indicates RoHS status only.

Package drawings may show a different suffix character, but the

drawing pertains to the package regardless of RoHS status.

PART TEMP RANGE PIN-PACKAGE

MAX7370ETG+ -40NC to +85NC24 TQFN-EP*

MAX7370EWA+** -40NC to +85NC25 WLP

PACKAGE

TYPE

PACKAGE

CODE

OUTLINE

NO.

LAND

PATTERN NO.

24 TQFN-EP T243A3+1 21-0188 90-0122

25 WLP W252F2+1 21-0453

Refer to

Application

Note 1891

MAX7370

8 x 8 Key-Switch Controller and LED Driver/GPIOs

with I2C Interface and High Level of ESD Protection

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent

licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and

max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 37

Revision History

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

0 6/11 Initial release —

1 3/12 Updated ESD protection specifications 1, 4, 8, 19

2 5/15 Updated Table 1 8

Mouser Electronics

Authorized Distributor

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Maxim Integrated:

MAX7370ETG+ MAX7370ETG+T