DS1631AU+ - Maxim Integrated - Datasheet.Technology

See Table 2 for Pin Descriptions.

General Description

The DS1631, DS1631A, and DS1731 digital thermome-

ters provide 9, 10, 11, or 12-bit temperature readings over

a -55°C to +125°C range. The DS1631 and DS1631A

thermometer accuracy is ±0.5°C from 0°C to +70°C with

3.0V ≤ VDD ≤ 5.5V, and the DS1731 accuracy is ±1°C

from -10°C to +85°C with 3.0V ≤ VDD ≤ 5.5V. The ther-

mostat on all three devices provides custom hysteresis

with user-defined trip points (TH and TL). The TH and

TL registers and thermometer configuration settings are

stored in NV EEPROM so they can be programmed prior

to installation. In addition, the DS1631A automatically

begins taking temperature measurements at power-up,

which allows it to function as a stand-alone thermostat.

Pin descriptions for the DS1631/DS1631A/DS1731 are pro-

vided in Table 2 and user-accessible registers are summa-

rized in Table 3. A functional diagram is shown in Figure 1.

Applications

●Network Routers and Switches

●Cellular Base Stations

●Portable Products

●Any Space-Constrained Thermally Sensitive Product

Benets and Features

●Maximize System Accuracy in Broad Range of

Thermal Management Applications

• Operating Temperature Range: -55°C to +125°C

(-67°F to +257°F)

• DS1631 and DS1631A: ±0.5°C Accuracy over 0°C

to +70°C Range

• DS1731: ±1°C Accuracy over a -10°C to +85°C Range

• User-Selectable Output Resolution from 9 Bits to

12 Bits

●Reduce Cost with No External Components

●Simplify Distributed Temperature-Sensing Applications

with Multidrop Capability

• Up to Eight Devices Can Operate on a 2-Wire Bus

●Flexible and Nonvolatile User-Defined Thermostatic

Modes with Custom Hysteresis

●Available in 8-Pin µSOP and SO (DS1631 and

DS1631A Only) and the 8-Pin DIP (DS1631 Only)

Packages

Ordering Information appears at end of data sheet.

19-7488; Rev 1; 1/15

Pin Congurations

SDA

SCL

OUT

GND

DS1631

µSOP

(DS1631U+, DS1631AU+, DS1731U+)

TOP VIEW

SDA

SCL

OUT

GND

DS1631

SO (150mil and 208mil)

(DS1631Z+, DS1631S+)

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

Voltage on any Pin Relative to Ground ................ -0.5V to +6.0V

Operating Temperature Range ......................... -55°C to +125°C

Storage Temperature Range ............................ -55°C to +125°C

Solder Dip Temperature (10s) .......See IPC/JEDEC J-STD-020A

Specification

Reflow Oven Temperature ...............................................+220°C

(VDD = 2.7V to 5.5V; TA = -55°C to +125°C.)

PARAMETER SYMBOL CONDITION MIN MAX UNITS

Supply Voltage VDD (Note 1) 2.7 5.5 V

DS1631, DS1631A

Thermometer Error (Note 2) TERR

0°C to +70°C,

3.0V ≤ VDD ≤ 5.5V ±0.5

°C

0°C to +70°C,

2.7V ≤ VDD < 3.0V ±1

-55°C to +125°C ±2

DS1731 Thermometer Error

(Note 2) TERR

-10°C to +85°C,

3.0V ≤ VDD ≤ 5.5V ±1

°C

-10°C to +85°C,

2.7V ≤ VDD < 3.0V ±1.5

-55°C to +125°C ±2

Low-Level Input Voltage VIL -0.5 0.3 x VDD V

High-Level Input Voltage VIH 0.7 x VDD VDD + 0.3 V

SDA Low-Level Output

Voltage

VOL1 3mA sink current 0 0.4 V

VOL2 6mA sink current 0 0.6

Input Current Each I/O Pin 0.4 < VI/O < 0.9VDD -10 +10 µA

Active Supply Current (Note 3) IDD

Temperature conversion

-55°C to +85°C 1

Temperature conversion

+85°C to +125°C 1.25

E2 write 400 µA

Communication only 110

Standby Supply Current ISTBY 0°C to +70°C (Note 4) 800 nA

TOUT Output Logic Voltage VOH 1mA source current (Note 1) 2.4 V

VOL 4mA sink current (Note 1) 0.4 V

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

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Absolute Maximum Ratings

*These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure

to absolute maximum rating conditions for extended periods of time may affect reliability.

DC Electrical Characteristics

(VDD = 2.7V to 5.5V; TA = -55°C to +125°C.)

Note 1: All voltages are referenced to GND.

Note 2: See Figure 2 for Typical Operating Curves.

Note 3: Specified with TOUT pin open; A0, A1, A2 = 0V or VDD; and fSCL ≥ 2Hz.

Note 4: Specified with temperature conversions stopped; TOUT pin open; SDA = VDD; SCL = VDD; and A0, A1, A2 = 0V or VDD.

Note 5: See Timing Diagram in Figure 3. All timing is referenced to 0.9 x VDD and 0.1 x VDD.

Note 6: After this period the first clock pulse is generated.

Note 7: For example, if CB = 300pF, then tR[min] = tF[min] = 50ns.

(VDD = 2.7V to 5.5V; TA = -55°C to +125°C.)

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS

Temperature Conversion Time tTC

9-bit resolution 93.75

10-bit resolution 187.5

11-bit resolution 375

12-bit resolution 750

SCL Frequency fSCL 0 400 kHz

Bus Free Time Between a STOP

and START Condition tBUF (Note 5) 1.3 µs

START and Repeated START

Hold Time from Falling SCL tHD:STA (Note 5, 6) 0.6 µs

Low Period of SCL tLOW (Note 5) 1.3 µs

High Period of SCL tHIGH (Note 5) 0.6 µs

Repeated START Condition

Setup Time to Rising SCL tSU:STA (Note 5) 0.6 µs

Data-Out Hold Time from

Falling SCL tHD:DAT (Note 5) 0 0.9 µs

Data-In Setup Time to

Rising SCL tSU:DAT (Note 5) 100 ns

Rise Time of SDA and SCL tR(Note 5, 7) 20 + 0.1CB1000 ns

Fall Time of SDA and SCL tF(Note 5, 7) 20 + 0.1CB300 ns

STOP Setup Time to Rising

SCL tSU:STO (Note 5) 0.6 µs

Capacitive Load for Each

Bus Line CB400 pF

I/O Capacitance CI/O 10 pF

Input Capacitance CI5 pF

Spike Pulse Width that can be

Suppressed by Input Filter tSP 0 50 ns

PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS

EEPROM Write Cycle Time twr 4 10 ms

EEPROM Writes NEEWR -55°C to +55°C 50k Writes

EEPROM Data Retention tEEDR -55°C to +55°C 10 Years

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

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AC Electrical Characteristics

EEPROM AC Electrical Characteristics

PIN SYMBOL DESCRIPTION

1 SDA Data Input/Output Pin for 2-Wire Serial Communication Port. Open-Drain.

2 SCL Clock Input Pin for 2-Wire Serial Communication Port.

3 TOUT Thermostat Output Pin. Push-Pull.

4 GND Ground Pin

5 A2Address Input Pin

6 A1Address Input Pin

7 A0Address Input Pin

8 VDD Supply Voltage Pin. +2.7V to +5.5V Power-Supply Pin.

Figure 1. Functional Diagram

Figure 2. Typical Operating Curves

ADDRESS

AND

I/O CONTROL

SCL

SDA

GND

CONFIGURATION REGISTER

AND CONTROL LOGIC

TEMPERATURE SENSOR

AND ∆Σ ADC

TEMPERATURE REGISTER

DIGITAL

COMPARATOR/LOGIC

OUT

DS1631

ERROR (°C)

0.8

0.6

0.4

0.2

-0.2

-0.4

-0.6

-0.8

0 10 20 30 40 50 60 70

REFERENCE TEMPERATURE (°C)

DS1631/DS1631A

+3σ

MEAN

-3σ

ERROR (°C)

0.8

-10

REFERENCE TEMPERATURE (°C)

0.6

0.4

0.2

-0.2

-0.4

-0.6

-0.8

0 10 20 30 40 50 60 70 80

DS1731

+3σ

MEAN

-3σ

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

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Table 2. Detailed Pin Description

Table 3. Register Summary

(USER ACCESS)

SIZE

(BYTES)

MEMORY

TYPE

AND POWER-UP STATE

Temperature (Read Only) 2 SRAM Measured temperature in two’s complement format.

Power-up state: -60ºC (1100 0100 0000 0000)

TH (Read/Write) 2 EEPROM Upper alarm trip point in two’s complement format.

Factory state: 15ºC (0000 1111 0000 0000)

TL (Read/Write) 2 EEPROM Lower alarm trip point in two’s complement format.

Factory state: 10ºC (0000 1010 0000 0000)

Conguration (Various bits are Read/

Write and Read Only—See Table 5) 1SRAM,

EEPROM

Conguration and status information. Unsigned data.

6 MSbs = SRAM

2 LSbs (POL and 1SHOT bits) = EEPROM

Power-up state: 100011XX (XX = user dened)

Figure 3. Timing Diagram

ALL TIMING IS REFERENCED TO 0.9 X V

AND 0.1 x V

SDA

STOP

SCL

START REPEATED

START

BUF

LOW

HD:STA

HD:DAT

HIGH

SU:DAT

SU:STA

SU:STO

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

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Operation—Measuring Temperature

The DS1631, DS1631A, and DS1731 measure tempera-

ture using bandgap-based temperature sensors. A delta-

sigma analog-to-digital converter (ADC) converts the

measured temperature to a 9-, 10-, 11-, or 12-bit (user-

selectable) digital value that is calibrated in °C; for °F

applications a lookup table or conversion routine must be

used. Throughout this data sheet, the term “conversion” is

used to refer to the entire temperature measurement and

ADC sequence.

The DS1631 and DS1731 always power-up in a low-pow-

er idle state, and the Start Convert T command must be

used to initiate conversions. The DS1631A begins conver-

sions automatically at power-up in the mode determined

by the configuration register’s 1SHOT bit.

The DS1631, DS1631A, and DS1731 can be programmed

to perform continuous consecutive conversions (continu-

ous-conversion mode) or to perform single conversions

on command (one-shot mode). The conversion mode is

programmed through the 1SHOT bit in the configuration

tion of this data sheet. In continuous-conversion mode,

the DS1631A begins performing continuous conversions

immediately at power-up, and the DS1631 and DS1731

begin continuous conversions after a Start Convert T

command is issued. For all three devices, consecu-

tive conversions continue to be performed until a Stop

Convert T command is issued, at which time the device

goes into a low-power idle state. Continuous conversions

can be restarted at any time using the Start Convert T

command.

In one-shot mode the DS1631A performs a single con-

version at power-up, and the DS1631 and DS1731

perform a single temperature conversion when a Start

Convert T command is issued. For all three devices,

when the conversion is complete the device enters a

low-power idle state and remains in that state until a

single temperature conversion is again initiated by a Start

Convert T command.

The resolution of the output digital temperature data is

user-configurable to 9, 10, 11, or 12 bits, corresponding

to temperature increments of 0.5°C, 0.25°C, 0.125°C, and

0.0625°C, respectively. The default resolution at power-

up is 12 bits, and it can be changed through the R0 and

R1 bits in the configuration register. Note that the conver-

sion time doubles for each additional bit of resolution.

After each conversion, the digital temperature is stored

as a 16-bit two’s complement number in the two-byte

temperature register as shown in Figure 4. The sign bit

(S) indicates if the temperature is positive or negative:

for positive numbers S = 0 and for negative numbers

S = 1. The Read Temperature command provides user

access to the temperature register. Bits 3 through 0 of

the temperature register are hardwired to 0. When the

device is configured for 12-bit resolution, the 12 MSbs

(bits 15 through 4) of the temperature register contain

temperature data. For 11 bit resolution, the 11 MSbs (bits

15 through 5) of the temperature register contain data,

and bit 4 is 0. Likewise, for 10-bit resolution, the 10 MSbs

(bits 15 through 6) contain data, and for 9-bit the 9 MSbs

(bits 15 through 7) contain data, and all unused LSbs con-

tain 0s. Table 4 gives examples of 12-bit resolution output

data and the corresponding temperatures.

Table 4. 12-Bit Resolution Temperature/

Data Relationship

TEMPERATURE

(°C)

DIGITAL OUTPUT

(BINARY)

DIGITAL

OUTPUT (HEX)

+125 0111 1101 0000 0000 7D00h

+25.0625 0001 1001 0001 0000 1910h

+10.125 0000 1010 0010 0000 0A20h

+0.5 0000 0000 1000 0000 0080h

0 0000 0000 0000 0000 0000h

-0.5 1111 1111 1000 0000 FF80h

-10.125 1111 0101 1110 0000 F5E0h

-25.0625 1110 0110 1111 0000 E6F0h

-55 1100 1001 0000 0000 C900h

Figure 4. Temperature, TH, And TL Register Format

BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8

MS BYTE S 26252423222120

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

LS BYTE 2-1 2-2 2-3 2-4 0000

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

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Operation—Thermostat Function

The thermostat output (TOUT) is updated after every

temperature conversion, based on a comparison between

the measured digital temperature and user-defined upper

and lower thermostat trip points. TOUT remains at the

updated value until the next conversion completes. When

the measured temperature meets or exceeds the value

stored in the upper trip-point register (TH), TOUT becomes

active and remains active until the measured temperature

falls below the value stored in the lower trip-point register

(TL) (see Figure 5). This allows the user to program any

amount of hysteresis into the output response. The active

state of TOUT is user-programmable through the polarity

bit (POL) in the configuration register.

The user-defined values in the TH and TL registers (see

Figure 4) must be in two’s complement format with the

MSb (bit 15) containing the sign bit (S). The TH and TL

resolution is determined by the R0 and R1 bits in the

configuration register (see Table 6), so the TH and TL

resolution matches the output temperature resolution. For

example, for 10-bit resolution bits 5 through 0 of the TH

and TL registers read out as 0 (even if 1s are written to

these bits), and the converted temperature is compared

to the 10 MSbs of TH and TL.

The TH and TL registers are stored in EEPROM; there-

fore, they are NV and can be programmed prior to device

installation. Writing to and reading from the TH and TL

registers is achieved using the Access TH and Access

TL commands. When making changes to the TH and TL

registers, conversions should first be stopped using the

Stop Convert T command if the device is in continuous

conversion mode. Note that if the thermostat function is

not used, the TH and TL registers can be used as general-

purpose NV memory.

Another thermostat feature is the temperature high and

low flags (THF and TLF) in the configuration register.

These bits provide a record of whether the temperature

has been greater than TH or less than TL at anytime since

the device was powered up. These bits power up as 0s,

and if the temperature ever exceeds the TH register value,

the THF bit is set to 1, or if the temperature ever falls

below the TL value, the TLF bit is set to 1. Once THF and/

or TLF has been set, it remains set until overwritten with a

0 by the user or until the power is cycled.

Ds1631A Stand-Alone

Thermostat Operation

Since the DS1631A automatically begins taking tem-

perature measurements at power-up, it can function as

a standalone thermostat (i.e., it can provide thermostatic

operation without microcontroller communication). For

standalone operation, the NV TH and TL registers and the

POL and 1SHOT bits in the configuration register should

be programmed to the desired values prior to installation.

Since the default conversion resolution at power-up is 12

bits (R1 = 1 and R0 = 1 in the configuration register), the

conversion resolution is always 12 bits during standalone

thermostat operation.

Conguration Register

The configuration register allows the user to program

various DS1631 options such as conversion resolution,

TOUT polarity, and operating mode. It also provides infor-

mation to the user about conversion status, EEPROM

activity, and thermostat activity. The configuration register

is arranged as shown in Figure 6 and detailed descrip-

tions of each bit are provided in Table 5. This register

can be read from and written to using the Access Config

command. When writing to the configuration register, con-

versions should first be stopped using the Stop Convert T

command if the device is in continuous conversion mode.

Note that the POL and 1SHOT bits are stored in EEPROM

so they can be programmed prior to installation is desired.

All other configuration register bits are SRAM and power

up in the state shown in Table 5.

Figure 5. Thermostat Output Operation

Figure 6. Configuration Register

TEMP

OUT

POL = 1 (T

OUT

IS ACTIVE HIGH)

LOGIC 1

LOGIC 0

MSB BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 LSB

DONE THF TLF NVB R1 R0 POL* 1SHOT*

*NV (EEPROM)

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

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Table 5. Configuration Register Bit Descriptions

Table 6. Resolution Configuration

*Stored in EEPROM

BIT NAME (USER ACCESS) FUNCTIONAL DESCRIPTION

DONE—Temperature Conversion

Done (Read Only)

Power-up state = 1.

DONE = 0. Temperature conversion is in progress.

DONE = 1. Temperature conversion is complete.

THF—Temperature High Flag

(Read/Write)

Power-up state = 0.

THF = 0. The measured temperature has not exceeded the value stored in the TH

THF = 1. At some point since power-up the measured temperature has been higher

than the value stored in the TH register. THF remains a 1 until it is overwritten with a 0

by the user, the power is cycled, or a Software POR command is issued.

TLF—Temperature Low Flag

(Read/Write)

Power-up state = 0.

TLF = 0. The measured temperature has not been lower than the value stored in the TL

TLF = 1. At some point since power-up the measured temperature has been lower than

the value stored in the TL register. TLF remains a 1 until it is overwritten with a 0 by the

user, the power is cycled, or a Software POR command is issued.

NVB—NV Memory Busy

(Read Only)

Power-up state = 0.

NVB = 1. A write to EEPROM memory is in progress.

NVB = 0. NV memory is not busy.

R1—Resolution Bit 1 (Read/Write) Power-up state = 1.

Sets conversion, TH, and TL resolution (see Table 6).

R0—Resolution Bit 0 (Read/Write) Power-up state = 1.

Sets conversion, TH, and TL resolution (see Table 6).

POL*—TOUT Polarity (Read/Write)

Power-up state = last value written to this bit. Factory setting = 0.

POL = 1. TOUT is active high.

POL = 0. TOUT is active low.

1SHOT*—Conversion Mode

(Read/Write)

Power-up state = last value written to this bit. Factory setting = 0.

1SHOT = 1. One-Shot Mode. The Start Convert T command initiates a single

temperature conversion and then the device goes into a low-power standby state.

1SHOT = 0. Continuous Conversion Mode. The Start Convert T command initiates

continuous temperature conversions.

R1 R0 RESOLUTION (BIT) CONVERSION TIME (MAX)

0 0 9 93.75ms

0 1 10 187.5ms

1 0 11 375ms

1 1 12 750ms

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

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2-Wire Serial Data Bus

The DS1631, DS1631A, and DS1731 communicate over

a bidirectional 2-wire serial data bus that consists of a

serial clock (SCL) signal and serial data (SDA) signal.

The DS1631, DS1631A, and DS1731 interface to the bus

through their SCL input pins and open-drain SDA I/O pins.

The following terminology is used to describe 2-wire com-

munication:

Master Device: Microprocessor/microcontroller that con-

trols the slave devices on the bus. The master device gen-

erates the SCL signal and START and STOP conditions.

Slave:

All devices on the bus other than the master. The

DS1631, DS1631A, and DS1731 always function as

slaves.

Bus Idle or Not Busy:

Both SDA and SCL remain high.

SDA is held high by a pullup resistor when the bus is idle,

and SCL must either be forced high by the master (if the

SCL output is push-pull) or pulled high by a pullup resistor

(if the SCL output is open-drain).

Transmitter:

A device (master or slave) that is sending

data on the bus.

Receiver:

A device (master or slave) that is receiving data

from the bus.

START Condition:

Signal generated by the master to

indicate the beginning of a data transfer on the bus. The

master generates a START condition by pulling SDA from

high to low while SCL is high (see Figure 8). A “repeated”

START is sometimes used at the end of a data transfer

(instead of a STOP) to indicate that the master will per-

form another operation.

STOP Condition: Signal generated by the master to

indicate the end of a data transfer on the bus. The master

generates a STOP condition by transitioning SDA from low

to high while SCL is high (see Figure 8). After the STOP is

issued, the master releases the bus to its idle state.

Acknowledge (ACK):

When a device is acting as a

receiver, it must generate an acknowledge (ACK) on the

SDA line after receiving every byte of data. The receiv-

ing device performs an ACK by pulling the SDA line low

for an entire SCL period (see Figure 8). During the ACK

clock cycle, the transmitting device must release SDA.

A variation on the ACK signal is the “not acknowledge”

(NACK). When the master device is acting as a receiver,

it uses a NACK instead of an ACK after the last data byte

to indicate that it is finished receiving data. The master

indicates a NACK by leaving the SDA line high during the

ACK clock cycle.

Slave Address:

Every slave device on the bus has a

unique 7-bit address that allows the master to access

that device. The 7-bit bus address is 1 0 0 1 A2 A1 A0,

where A2, A1, and A0 are user-selectable through the

corresponding input pins. The three address pins allow

up to eight DS1631s, DS1631As, or DS1731s to be mul-

tidropped on the same bus.

Control Byte: The control byte is transmitted by the mas-

ter and consists of the 7-bit slave address plus a read/

write (R/W) bit (see Figure 7). If the master is going to read

data from the slave device then R/W = 1, and if the master

is going to write data to the slave device then R/W = 0.

Command Byte:

The command byte can be any of the

command protocols described in the Command Set sec-

tion of this data sheet.

Figure 7. Control Byte

Figure 8. START, STOP, and ACK signals

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

1 0 0 1 A2A1A0R/W

SDA

SCL

START

CONDITIONS

ACK (OR NACK)

FROM RECEIVER

STOP

CONDITION

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

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General 2-Wire Information

● All data is transmitted MSb rst over the 2-wire bus.

●One bit of data is transmitted on the 2-wire bus each

SCL period.

●A pullup resistor is required on the SDA line and,

when the bus is idle, both SDA and SCL must remain

in a logic-high state.

●All bus communication must be initiated with a START

condition and terminated with a STOP condition. Dur-

ing a START or STOP is the only time SDA is allowed

to change states while SCL is high. At all other times,

changes on the SDA line can only occur when SCL is

low: SDA must remain stable when SCL is high.

●After every 8-bit (1-byte) transfer, the receiving device

must answer with an ACK (or NACK), which takes

one SCL period. Therefore, nine clocks are required

for every one-byte data transfer.

Initiating 2-Wire Communication

To initiate 2-wire communication, the master generates a

START followed by a control byte containing the DS1631,

DS1631A, or DS1731 slave address. The R/W bit of the

control byte must be a 0 (“write”) since the master next

writes a command byte. The DS1631/DS1631A/DS1731

responds with an ACK after receiving the control byte.

This must be followed by a command byte from the mas-

ter, which indicates what type of operation is to be per-

formed. The DS1631/DS1631A/DS1731 again respond

with an ACK after receiving the command byte.

If the command byte is a Start Convert T or Stop Convert

T command (see Figure 9), the transaction is finished,

and the master must issue a STOP to signal the end of

the communication sequence. If the command byte indi-

cates a write or read operation, additional actions must

occur as explained in the following sections.

2-Wire Writes

The master can write data to the DS1631/DS1631A/

DS1731 by issuing an Access Config, Access TH, or

Access TL command following the control byte (see

Figures 9b and 9d). Since the R/W bit in the control byte

was a 0 (“write”), the DS1631/DS1631A/DS1731 are

already prepared to receive data. Therefore, after receiv-

ing an ACK in response to the command byte, the master

device can immediately begin transmitting data. When

writing to the configuration register, the master must

send one byte of data, and when writing to the TH or TL

registers the master must send two bytes of data. After

receiving each data byte, the DS1631/DS1631A/DS1731

respond with an ACK, and the transaction is finished with

a STOP from the master.

2-Wire Reads

The master can read data from the DS1631/DS1631A/

DS1731 by issuing an Access Config, Access TH, Access

TL, or Read Temperature command following the control

byte (see Figures 9c and 9e). After receiving an ACK in

response to the command, the master must generate

a repeated START followed by a control byte with the

same slave address as the first control byte. However,

this time the R/W bit must be a 1, which tells the DS1631/

DS1631A/DS1731 that a “read” is being performed. After

the DS1631/DS1631A/DS1731 send an ACK in response

to this control byte, it begins transmitting the requested

data on the next clock cycle. One byte of data will be trans-

mitted when reading from the configuration register after

which the master must respond with a NACK followed by a

STOP. For two-byte reads (i.e., from the Temperature, T

or T

byte with an ACK and to the second byte with a NACK fol-

lowed by a STOP. If only the most significant byte of data

is needed, the master can issue a NACK followed by a

STOP after reading the first data byte.

Command Set

The DS1631/DS1631A/DS1731 command set is detailed

below:

Start Convert T [ 51h ]

Initiates temperature conversions. If the part is in one-shot

mode (1SHOT = 1), only one conversion is performed. In

continuous mode (1SHOT = 0), continuous temperature

conversions are performed until a Stop Convert T com-

mand is issued.

Stop Convert T [ 22h ]

Stops temperature conversions when the device is in

continuous conversion mode (1SHOT = 0).

Read Temperature [ AAh ]

Reads last converted temperature value from the 2-byte

temperature register.

Access TH [ A1h ]

Reads or writes the 2-byte TH register.

Access TL [ A2h ]

Reads or writes the 2-byte TL register.

Access Config [ ACh ]

Reads or writes the 1-byte configuration register.

Software POR [ 54h ]

Initiates a software power-on-reset (POR), which stops

temperature conversions and resets all registers and

logic to their power-up states. The software POR allows

the user to simulate cycling the power without actually

powering down the device.

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

www.maximintegrated.com Maxim Integrated

│

Figure 9. (a, b, c, d, e). 2-Wire Interface Timing

D6 D5 D4 D3 D1 D0A0 W AA1 1 0 1 0 1 1 0 0 A D7A2S 1 10 0 P

A) ISSUE A "START CONVERT T” OR “STOP CONVERT T” COMMAND

SCL

SDA S 1 0 0 1 A2 A1 A0 W A C7 C6 C5 C4 C3 C2 C1 C0 A P

STOP

ACK

(THERM)

COMMAND BYTE

ACK

(THERM)

CONTROL BYTE

START

B) WRITE TO THE CONFIGURATION REGISTER

SCL

SDA

ACK

(THERM)

COMMAND BYTE

ACK

(THERM)

CONTROL BYTE

START DATA BYTE

(FROM MASTER)

STOP

ACK

(THERM)

C) READ FROM THE CONFIGURATION REGISTER

SCL

SDA S 1 0 0 A0 W AA1 1 0 1 0 1 1 0 0 AA2

1S 1 0 0 1 A2 A1 A0 R A D7 D6 D5 D4 D3 D2 D1 D0 N P

ACK

(THERM)

COMMAND BYTE

ACK

(THERM)

CONTROL BYTE

START REPEAT

START

CONTROL BYTE ACK

(THERM)

DATA BYTE

(FROM THERM)

NACK

(MASTER)

STOP

SCL

SDA S 1 0 0 A0 W AA1A2

D) WRITE TO THE T

OR T

C7 C6 C5 C4 C3 C2 C1 C0 AD7 D6 D5 D4 D3 D2 D1 D0 A D7 D6 D5 D4 D3 D2 D1 D0 A P

COMMAND BYTE

ACK

(THERM)

CONTROL BYTE

START ACK

(THERM)

MS DATA BYTE

(FROM MASTER)

ACK

(THERM)

LS DATA BYTE

(FROM MASTER)

ACK

(THERM)

STOP

E) READ FROM THE TEMPERATURE, T

, OR T

SCL

SDA S 1 0 0 1 A2 A1 A0 W A C7 C6 C5 C4 C3 C2 C1 C0 A S 1 0 0 1 A2 A1 A0 R A D7 D6 D5 D4 D3 D2 D1 D0 A

ACK

(THERM)

COMMAND BYTE

ACK

(THERM)

CONTROL BYTE

START REPEAT

START

CONTROL BYTE ACK

(THERM)

MS DATA BYTE

(FROM THERM)

ACK

(MASTER)

D5 N

D6 D4 D3 D2 D1 D0 P

…

LS DATA BYTE

(FROM THERM)

NACK

(MASTER)

STOP

THERM = DS1631, DS1631A, or DS1731

DS1631/DS1631A/

DS1731

High-Precision Digital

Thermometer and Thermostat

www.maximintegrated.com Maxim Integrated

│

Operation Example

In this example, the master configures the DS1631/DS1631A/DS1731 (A1A2A3 = 000) for continuous conversions and

thermostatic function.

*THERMOMETER = DS1631, DS1631A, or DS1731

MASTER

MODE

THERMETER*

MODE

DATA

(MSB FIRST)COMMENTS

TX RX START START condition from MASTER.

TX RX 90h MASTER sends control byte with R/W = 0.