LTC4444-5IMS8E#TRPBF - Linear Technology Corporation

LTC4444-5

44445f

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

High Voltage Synchronous

N-Channel MOSFET Driver

The LTC

4444-5 is a high frequency high voltage gate

driver that drives two N-channel MOSFETs in a synchro-

nous DC/DC converter with supply voltages up to 100V.

The powerful driver capability reduces switching losses

in MOSFETs with high gate capacitance. The LTC4444-5’s

pull-up for the top gate driver has a peak output current

of 1.4A and its pull-down has an output impedance of

1.5Ω. The pull-up for the bottom gate driver has a peak

output current of 1.75A and the pull-down has an output

impedance of 0.75Ω.

The LTC4444-5 is conﬁ gured for two supply-indepen-

dent inputs. The high side input logic signal is internally

level-shifted to the bootstrapped supply, which may func-

tion at up to 114V above ground.

The LTC4444-5 contains undervoltage lockout circuits

that disable the external MOSFETs when activated.

The LTC4444-5 also contains adaptive shoot-through

protection to prevent both MOSFETs from conducting

simultaneously.

The LTC4444-5 is available in the thermally enhanced

8-lead MSOP package.

For a similar driver in this product family, please refer to

the chart below.

PARAMETER LTC4444-5 LTC4446 LTC4444

Shoot-Through Protection Yes No Yes

Absolute Max TS 100V 100V 100V

MOSFET Gate Drive 4.5V to 13.5V 7.2V to 13.5V 7.2V to 13.5V

VCC UV+4V 6.6V 6.6V

VCC UV–3.5V 6.15V 6.15V

■ Bootstrap Supply Voltage to 114V

■ Wide VCC Voltage: 4.5V to 13.5V

■ Adaptive Shoot-Through Protection

■ 1.4A Peak Top Gate Pull-Up Current

■ 1.75A Peak Bottom Gate Pull-Up Current

■ 1.5Ω Top Gate Driver Pull-Down

■ 0.75Ω Bottom Gate Driver Pull-Down

■ 5ns Top Gate Fall Time Driving 1nF Load

■ 8ns Top Gate Rise Time Driving 1nF Load

■ 3ns Bottom Gate Fall Time Driving 1nF Load

■ 6ns Bottom Gate Rise Time Driving 1nF Load

■ Drives Both High and Low Side N-Channel MOSFETs

■ Undervoltage Lockout

■ Thermally Enhanced 8-Pin MSOP Package

■ Distributed Power Architectures

■ Automotive Power Supplies

■ High Density Power Modules

■ Telecommunication Systems

High Input Voltage Buck Converter LTC4444-5 Driving a 1000pF Capacitive Load

L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Protected by U.S. Patents including 6677210.

BOOST

VIN

100V

GND

VCC

TINP

LTC4444-5

PWM2

(FROM CONTROLLER IC)

PWM1

(FROM CONTROLLER IC)

VCC

4.5V TO 13.5V

BINP

VOUT

44445 TA01a

BINP

5V/DIV

TINP

5V/DIV

TG-TS

5V/DIV

20ns/DIV 44445 TA01b

LTC4444-5

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PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS

Supply Voltage

CC ......................................................... –0.3V to 14V

BOOST – TS ........................................... –0.3V to 14V

TINP Voltage ................................................. –2V to 14V

BINP Voltage ................................................. –2V to 14V

BOOST Voltage ........................................ –0.3V to 114V

TS Voltage ................................................... –5V to 100V

Operating Temperature Range (Note 2).... –40°C to 85°C

Junction Temperature (Note 3) ............................. 125°C

Storage Temperature Range ................... –65°C to 150°C

Lead Temperature (Soldering, 10 sec) .................. 300°C

(Note 1)

TINP

BINP

VCC

BOOST

TOP VIEW

MS8E PACKAGE

8-LEAD PLASTIC MSOP

TJMAX = 125°C, θJA = 40°C/W, θJC = 10°C/W (NOTE 4)

EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

ELECTRICAL CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Gate Driver Supply, VCC

VCC Operating Voltage 4.5 13.5 V

IVCC DC Supply Current TINP = BINP = 0V 320 520 μA

UVLO Undervoltage Lockout Threshold VCC Rising

VCC Falling

Hysteresis

●

3.60

3.20

4.00

3.55

450

4.40

3.90

Bootstrapped Supply (BOOST – TS)

IBOOST DC Supply Current TINP = BINP = 0V 0.1 2 μA

Input Signal (TINP, BINP)

VIH(BG) BG Turn-On Input Threshold BINP Ramping High ●2.25 2.75 3.25 V

VIL(BG) BG Turn-Off Input Threshold BINP Ramping Low ●1.85 2.3 2.75 V

VIH(TG) TG Turn-On Input Threshold TINP Ramping High ●2.25 2.75 3.25 V

VIL(TG) TG Turn-Off Input Threshold TINP Ramping Low ●1.85 2.3 2.75 V

ITINP(BINP) Input Pin Bias Current ±0.01 ±2 μA

The ● denotes the speciﬁ cations which apply over the full operating

temperature range, otherwise speciﬁ cations are at TA = 25°C. VCC = VBOOST = 6V, VTS = GND = 0V, unless otherwise noted.

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LTC4444-5EMS8E#PBF LTC4444-5EMS8E#TRPBF LTDPY 8-Lead Plastic MSOP –40°C to 85°C

LTC4444-5IMS8E#PBF LTC4444-5IMS8E#TRPBF LTDPY 8-Lead Plastic MSOP –40°C to 85°C

Consult LTC Marketing for parts speciﬁ ed with wider operating temperature ranges. *The temperature grade is identiﬁ ed by a label on the shipping container.

Consult LTC Marketing for information on non-standard lead based ﬁ nish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁ cations, go to: http://www.linear.com/tapeandreel/

LTC4444-5

44445f

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2: The LTC4444-5E is guaranteed to meet speciﬁ cations from

0°C to 85°C. Speciﬁ cations over the –40°C to 85°C operating

temperature range are assured by design, characterization and correlation

with statistical process controls. The LTC4444-5I is guaranteed over the

full –40°C to 85°C operating temperature range.

ELECTRICAL CHARACTERISTICS

The ● denotes the speciﬁ cations which apply over the full operating

temperature range, otherwise speciﬁ cations are at TA = 25°C. VCC = VBOOST = 6V, VTS = GND = 0V, unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

High Side Gate Driver Output (TG)

VOH(TG) TG High Output Voltage ITG = –10mA, VOH(TG) = VBOOST – VTG 0.7 V

VOL(TG) TG Low Output Voltage ITG = 100mA, VOL(TG) = VTG –VTS ●150 250 mV

IPU(TG) TG Peak Pull-Up Current ●1 1.4 A

RDS(TG) TG Pull-Down Resistance ●1.5 2.5 Ω

Low Side Gate Driver Output (BG)

VOH(BG) BG High Output Voltage IBG = –10mA, VOH(BG) = VCC – VBG 0.7 V

VOL(BG) BG Low Output Voltage IBG = 100mA ●75 130 mV

IPU(BG) BG Peak Pull-Up Current ●1.15 1.75 A

RDS(BG) BG Pull-Down Resistance ●0.75 1.3 Ω

Switching Time (BINP (TINP) is Tied to Ground While TINP (BINP) is Switching. Refer to Timing Diagram)

tPLH(TG) TG Low-High Propagation Delay ●33 55 ns

tPHL(TG) TG High-Low Propagation Delay ●24 40 ns

tPLH(BG) BG Low-High Propagation Delay ●27 45 ns

tPHL(BG) BG High-Low Propagation Delay ●15 30 ns

tr(TG) TG Output Rise Time 10% – 90%, CL = 1nF

10% – 90%, CL = 10nF

tf(TG) TG Output Fall Time 10% – 90%, CL = 1nF

10% – 90%, CL = 10nF

tr(BG) BG Output Rise Time 10% – 90%, CL = 1nF

10% – 90%, CL = 10nF

tf(BG) BG Output Fall Time 10% – 90%, CL = 1nF

10% – 90%, CL = 10nF

Note 3: TJ is calculated from the ambient temperature TA and power

dissipation PD according to the following formula:

J = TA + (PD • θJA°C/W)

Note 4: Failure to solder the exposed back side of the MS8E package to the

PC board will result in a thermal resistance much higher than 40°C/W.

LTC4444-5

44445f

TYPICAL PERFORMANCE CHARACTERISTICS

VCC Supply Quiescent Current

vs Voltage

BOOST-TS Supply Quiescent

Current vs Voltage

VCC Supply Current vs

Temperature

Boost Supply Current

vs Temperature

Output Low Voltage (VOL)

vs Supply Voltage

Output High Voltage (VOH) vs

Supply Voltage

Input Thresholds (TINP, BINP) vs

Supply Voltage

Input Thresholds (TINP, BINP) vs

Temperature

Input Thresholds (TINP, BINP)

Hysteresis vs Voltage

VCC SUPPLY VOLTAGE (V)

QUIESCENT CURRENT (μA)

150

200

250

6 7 8 9 10 11 12 13

450

44445 G01

100

12345 14

300

350

400 TINP = BINP = 0V

TINP (BINP) = 6V

TA = 25°C

BOOST = 6V

TS = GND

BOOST SUPPLY VOLTAGE (V)

QUIESCENT CURRENT (μA)

150

200

250

678910111213

400

44445 G02

100

12345 14

300

350

TINP = BINP = 0V

TINP = 6V, BINP = 0V

TINP = 0V, BINP = 6V

TA = 25°C

VCC = 6V

TS = GND

TEMPERATURE (°C)

–40

280

VCC SUPPLY CURRENT (μA)

285

295

300

305

50 65 80 95

325

44445 G03

290

–25 –10 5 20 35 125110

310

315

320

VCC = BOOST = 6V

TS = GND

TINP = BINP = 0V

TINP (BINP) = 6V

TEMPERATURE (°C)

BOOST SUPPLY CURRENT (μA)

250

300

350

44445 G04

150

–40 –25 –10 5 20 35 50 65 80 95 110 125

400

200

100

TINP = 6V, BINP = 0V

TINP = 0V, BINP = 6V

TINP = BINP = 0V

VCC = BOOST = 6V

TS = GND

SUPPLY VOLTAGE (V)

4.5

OUTPUT VOLTAGE (mV)

100

10.5 11.5 12.5 13.5

160

44445 G05

5.5 6.5 7.5 8.5 9.5

120

140 VOL(TG)

VOL(BG)

TA = 25°C

ITG(BG) = 100mA

BOOST = VCC

TS = GND

SUPPLY VOLTAGE (V)

4.5

TG OR BG OUTPUT VOLTAGE (V)

12.5

44445 G06

6.5 8.5 10.5

5.5 7.5 9.5 11.5 13.5

TA = 25°C

BOOST = VCC

TS = GND

–100mA

–1mA

–10mA

SUPPLY VOLTAGE (V)

1.8

TG OR BG INPUT THRESHOLD (V)

2.2

2.6

3.0

2.0

2.4

2.8

6.5 8.5 10.5 12.5

44445 G07

5.54.5 7.5 9.5 11.5 13.5

TA = 25°C

BOOST = VCC

TS = GND

VIH(TG,BG)

VIL(TG,BG)

TEMPERATURE (°C)

–25

TG OR BG INPUT THRESHOLD (V)

2.6

2.8

3.0

44445 G08

2.4

2.2

2.5

2.7

2.9

2.3

2.1

2.0 535 65

–10–40 110

20 50 80 125

VCC = BOOST = 6V

TS = GND

VIH(TG,BG)

VIL(TG,BG)

SUPPLY VOLTAGE (V)

4.5

TG OR BG INPUT THRESHOLD HYSTERESIS (mV)

500

475

450

425

400

375

350

325

300

12.5

44445 G09

6.5 8.5 10.5 11.55.5 7.5 9.5 13.5

TA = 25°C

BOOST = VCC

TS = GND

LTC4444-5

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TYPICAL PERFORMANCE CHARACTERISTICS

Input Thresholds (TINP, BINP)

Hysteresis vs Temperature

VCC Undervoltage Lockout

Thresholds vs Temperature

Rise and Fall Time vs

VCC Supply Voltage

Rise and Fall Time vs

Load Capacitance

Peak Driver (TG, BG) Pull-Up

Current vs Temperature

Output Driver Pull-Down

Resistance vs Temperature

Propagation Delay vs

VCC Supply Voltage Propagation Delay vs Temperature

TEMPERATURE (°C)

–40

TG OR BG INPUT THRESHOLD HYSTERESIS (mV)

450

475

500

44445 G10

425

400

375 –25 –10 5 20 35 50 65 11095 125

VCC = BOOST = 6V

TS = GND

TEMPERATURE (°C)

VCC SUPPLY VOLTAGE (V)

3.9

4.0

4.1

44445 G11

3.7

3.4

–40 –25 –10 5 20 35 50 65 80 95 110 125

4.2

3.8

3.6

3.5

RISING THRESHOLD

FALLING THRESHOLD

BOOST = VCC

TS = GND

SUPPLY VOLTAGE (V)

4.5

RISE/FALL TIME (ns)

6.5 8.5 9.5 13.5

5.5 7.5 10.5 11.5 12.5

44445 G12

TA = 25°C

BOOST = VCC

TS = GND

CL = 3.3nF tr(TG)

tf(TG)

tf(BG)

tr(BG)

LOAD CAPACITANCE (nF)

RISE/FALL TIME (ns)

44445 G13

0357

210

468

TA = 25°C

VCC = BOOST = 6V

TS = GND

tr(TG)

tf(TG)

tf(BG)

tr(BG)

TEMPERATURE (°C)

–40

PULL-UP CURRENT (A)

2.5

3.0

44445 G14

2.0

1.5

1.0 –25 –10 5 20 35 50 65 95 125110

IPU(BG)

VCC = 12V

IPU(BG)

VCC = 6V

IPU(TG)

BOOST–TS = 12V

IPU(TG)

BOOST–TS = 6V

TEMPERATURE (°C)

–25

OUTPUT DRIVER PULL-DOWN RESISTANCE (Ω)

1.2

1.8

2.6

44445 G15

0.8

0.4

1.0

1.4

2.2

1.6

2.4

2.0

0.6

0.2

0535 65

–10–40 110

20 50 80 125

BOOST–TS = 4.5V

VCC = 4.5V

VCC = 12V

BOOST–TS = 6V

BOOST–TS = 12V

VCC = 6V

RDS(TG)

RDS(BG)

SUPPLY VOLTAGE (V)

4.5

PROPAGATION DELAY (ns)

12.5

44445 G16

6.5 8.5 10.5 11.55.5 7.5 9.5 13.5

TA = 25°C

BOOST = VCC

TS = GND

tPLH(TG)

tPHL(TG)

tPHL(BG)

tPLH(BG)

TEMPERATURE (°C)

–25

PROPAGATION DELAY (ns)

44445 G17

2535 65

–10–40 110

20 50 80 125

tPLH(TG)

VCC = BOOST = 6V

TS = GND

tPHL(TG)

tPLH(BG)

tPHL(BG)

LTC4444-5

44445f

PIN FUNCTIONS

TYPICAL PERFORMANCE CHARACTERISTICS

Switching Supply Current vs

Input Frequency

Switching Supply Current vs

Load Capacitance

TINP (Pin 1): High Side Input Signal. Input referenced

to GND. This input controls the high side driver output

(TG).

BINP (Pin 2): Low Side Input Signal. This input controls

the low side driver output (BG).

VCC (Pin 3): Supply. This pin powers input buffers, logic

and the low side gate driver output directly and the high

side gate driver output through an external diode con-

nected between this pin and BOOST (Pin 6). A low ESR

ceramic bypass capacitor should be tied between this pin

and GND (Pin 9).

BG (Pin 4): Low Side Gate Driver Output (Bottom Gate).

This pin swings between VCC and GND.

NC (Pin 5): No Connect. No connection required.

BOOST (Pin 6): High Side Bootstrapped Supply. An ex-

ternal capacitor should be tied between this pin and TS

(Pin 8). Normally, a bootstrap diode is connected between

VCC (Pin 3) and this pin. Voltage swing at this pin is from

VCC – VD to VIN + VCC – VD, where VD is the forward volt-

age drop of the bootstrap diode.

TG (Pin 7): High Side Gate Driver Output (Top Gate). This

pin swings between TS and BOOST.

TS (Pin 8): High Side MOSFET Source Connection (Top

Source).

Exposed Pad (Pin 9): Ground. Must be soldered to PCB

ground for optimal thermal performance.

SWITCHING FREQUENCY (kHz)

SUPPLY CURRENT (mA)

0.2

0.6

0.8

1.0

400 800 1000

1.8

44445 G18

0.4

200 600

1.2

1.4

1.6

TA = 25°C

VCC = BOOST = 6V

TS = GND

IBOOST

(TG SWITCHING)

IVCC

(BG SWITCHING)

IVCC (TG SWITCHING)

IBOOST (BG SWITCHING)

LOAD CAPACITANCE (nF)

SUPPLY CURRENT (mA)

100

1000

1 579

34 6 8210

44445 G19

IVCC

(BG SWITCHING

AT 500kHz)

IBOOST (BG SWITCHING AT 500kHz)

IBOOST

(TG SWITCHING AT 1MHz)

IBOOST

(TG SWITCHING

AT 1MHz)

IVCC

(BG SWITCHING

AT 1MHz)

IVCC

(TG SWITCHING

AT 1MHz)

IVCC

(TG SWITCHING AT 500kHz)

LTC4444-5

44445f

BLOCK DIAGRAM

TIMING DIAGRAM

OPERATION

Overview

The LTC4444-5 receives ground-referenced, low voltage

digital input signals to drive two N-channel power MOSFETs

in a synchronous buck power supply conﬁ guration. The

gate of the low side MOSFET is driven either to VCC or GND,

depending on the state of the input. Similarly, the gate of

the high side MOSFET is driven to either BOOST or TS by

a supply bootstrapped off of the switching node (TS).

Input Stage

The LTC4444-5 employs CMOS compatible input thresholds

that allow a low voltage digital signal to drive standard

power MOSFETs. The LTC4444-5 contains an internal

voltage regulator that biases both input buffers for high

side and low side inputs, allowing the input thresholds

(VIH = 2.75V, VIL = 2.3V) to be independent of variations in

VCC. The 450mV hysteresis between VIH and VIL eliminates

false triggering due to noise during switching transitions.

However, care should be taken to keep both input pins

(TINP and BINP) from any noise pickup, especially in high

frequency, high voltage applications. The LTC4444-5 input

buffers have high input impedance and draw negligible

input current, simplifying the drive circuitry required for

the inputs.

9HIGH SIDE

LEVEL SHIFTER

VCC UVLO

LDO VINT

VCC

GND

4.5V TO

13.5V

BOOST VIN

UP TO 100V

44445 BD

1TINP

BINP

LOW SIDE

LEVEL SHIFTER

ANTISHOOT-THROUGH

PROTECTION

VCC VCC

90%

INPUT RISE/FALL TIME < 10ns

TINP (BINP)

BG (TG)

BINP (TINP)

TG (BG)

90% 90%

trtf

tPHL tPLH

10%

44445 TD

10%

LTC4444-5

44445f

OPERATION

Output Stage

A simpliﬁ ed version of the LTC4444-5’s output stage is

shown in Figure 1. The pull-up devices on the BG and

TG outputs are NPN bipolar junction transistors (Q1 and

Q2). The BG and TG outputs are pulled up to within an

NPN VBE (~0.7V) of their positive rails (VCC and BOOST,

respectively). Both BG and TG have N-channel MOSFET

pull-down devices (M1 and M2) which pull BG and TG

down to their negative rails, GND and TS. The large voltage

swing of the BG and TG output pins is important in driv-

ing external power MOSFETs, whose RDS(ON) is inversely

proportional to the gate overdrive voltage (VGS − VTH).

Rise/Fall Time

The LTC4444-5’s rise and fall times are determined by the

peak current capabilities of Q1 and M1. The predriver that

drives Q1 and M1 uses a nonoverlapping transition scheme

to minimize cross-conduction currents. M1 is fully turned

off before Q1 is turned on and vice versa.

Since the power MOSFET generally accounts for the ma-

jority of the power loss in a converter, it is important to

quickly turn it on or off, thereby minimizing the transition

time in its linear region. An additional beneﬁ t of a strong

pull-down on the driver outputs is the prevention of cross-

conduction current. For example, when BG turns the low

side (synchronous) power MOSFET off and TG turns the

high side power MOSFET on, the voltage on the TS pin

will rise to VIN very rapidly. This high frequency positive

voltage transient will couple through the CGD capacitance

of the low side power MOSFET to the BG pin. If there is

an insufﬁ cient pull-down on the BG pin, the voltage on

the BG pin can rise above the threshold voltage of the low

side power MOSFET, momentarily turning it back on. With

both the high side and low side MOSFETs conducting,

signiﬁ cant cross-conduction current will ﬂ ow through the

MOSFETs from VIN to ground and will cause substantial

power loss. A similar effect occurs on TG due to the CGS

and CGD capacitances of the high side MOSFET.

The powerful output driver of the LTC4444-5 reduces the

switching losses of the power MOSFET, which increase

with transition time. The LTC4444-5’s high side driver is

Figure 1. Capacitance Seen by BG and TG During Switching

capable of driving a 1nF load with 8ns rise and 5ns fall

times using a bootstrapped supply voltage VBOOST-TS of

12V while its low side driver is capable of driving a 1nF

load with 6ns rise and 3ns fall times using a supply volt-

age VCC of 12V.

Undervoltage Lockout (UVLO)

The LTC4444-5 contains an undervoltage lockout detector

that monitors VCC supply. When VCC falls below 3.55V,

the output pins BG and TG are pulled down to GND and

TS, respectively. This turns off both external MOSFETs.

When VCC has adequate supply voltage, normal operation

will resume.

Adaptive Shoot-Through Protection

Internal adaptive shoot-through protection circuitry moni-

tors the voltages on the external MOSFETs to ensure that

they do not conduct simultaneously. This feature improves

efﬁ ciency by eliminating cross-conduction current from

ﬂ owing from the VIN supply through both of the MOSFETs

to ground during a switch transition. The adaptive shoot-

through protection circuitry also monitors the level of the

TS pin. If the TS pin stays high, BG will be turned on 150ns

after TG is turned off.

BOOST

LTC4444-5

VIN

UP TO 100V

M1 CGS

CGD

VCC

GND

LOW SIDE

POWER

MOSFET

HIGH SIDE

POWER

MOSFET

CGS

CGD

LOAD

INDUCTOR

LTC4444-5

44445f

APPLICATIONS INFORMATION

Power Dissipation

To ensure proper operation and long-term reliability,

the LTC4444-5 must not operate beyond its maximum

temperature rating. Package junction temperature can

be calculated by:

J = TA + PD (θJA)

where:

J = Junction temperature

A = Ambient temperature

D = Power dissipation

θJA = Junction-to-ambient thermal resistance

Power dissipation consists of standby and switching

power losses:

D = PDC + PAC + PQG

where:

PDC = Quiescent power loss

PAC = Internal switching loss at input frequency, fIN

PQG = Loss due turning on and off the external MOSFET

with gate charge QG at frequency fIN

The LTC4444-5 consumes very little quiescent current.

The DC power loss at VCC = 12V and VBOOST-TS = 12V is

only (350μA)(12V) = 4.2mW.

At a particular switching frequency, the internal power loss

increases due to both AC currents required to charge and

discharge internal node capacitances and cross-conduc-

tion currents in the internal logic gates. The sum of the

quiescent current and internal switching current with no

load are shown in the Typical Performance Characteristics

plot of Switching Supply Current vs Input Frequency.

The gate charge losses are primarily due to the large AC

currents required to charge and discharge the capacitance

of the external MOSFETs during switching. For identical

pure capacitive loads CLOAD on TG and BG at switching

frequency fIN, the load losses would be:

CLOAD = (CLOAD)(f)[(VBOOST-TS)2 + (VCC)2]

In a typical synchronous buck conﬁ guration, VBOOST-TS

is equal to VCC – VD, where VD is the forward voltage

drop across the diode between VCC and BOOST. If this

drop is small relative to VCC, the load losses can be

approximated as:

CLOAD = 2(CLOAD)(fIN)(VCC)2

Unlike a pure capacitive load, a power MOSFET’s gate

capacitance seen by the driver output varies with its VGS

voltage level during switching. A MOSFET’s capacitive load

power dissipation can be calculated using its gate charge,

QG. The QG value corresponding to the MOSFET’s VGS

value (VCC in this case) can be readily obtained from the

manufacturer’s QG vs VGS curves. For identical MOSFETs

on TG and BG:

QG = 2(VCC)(QG)(fIN)

To avoid damage due to power dissipation, the LTC4444-5

includes a temperature monitor that will pull BG and TG

low if the junction temperature rises above 160°C. Normal

operation will resume when the junction temperature cools

to less than 135°C.

Bypassing and Grounding

The LTC4444-5 requires proper bypassing on the VCC

and VBOOST-TS supplies due to its high speed switching

(nanoseconds) and large AC currents (Amperes). Careless

component placement and PCB trace routing may cause

excessive ringing.

To obtain the optimum performance from the

LTC4444-5:

A. Mount the bypass capacitors as close as possible

between the VCC and GND pins and the BOOST and

TS pins. The leads should be shortened as much as

possible to reduce lead inductance.

B. Use a low inductance, low impedance ground plane

to reduce any ground drop and stray capacitance.

Remember that the LTC4444-5 switches greater than

3A peak currents and any signiﬁ cant ground drop will

degrade signal integrity.

LTC4444-5

44445f

APPLICATIONS INFORMATION

C. Plan the power/ground routing carefully. Know where

the large load switching current is coming from and

going to. Maintain separate ground return paths for

the input pin and the output power stage.

D. Keep the copper trace between the driver output pin

and the load short and wide.

E. Be sure to solder the Exposed Pad on the back side of

the LTC4444-5 package to the board. Correctly soldered

to a 2500mm2 doublesided 1oz copper board, the

LTC4444-5 has a thermal resistance of approximately

40°C/W for the MS8E package. Failure to make good

thermal contact between the exposed back side and

the copper board will result in thermal resistances far

greater than 40°C/W.

TYPICAL APPLICATION

LTC3780 High Efﬁ ciency 36V-72V VIN to 48V/6A Buck-Boost DC/DC Converter

Efﬁ ciency

PGOOD

SENSE+

SENSE–

ITH

VOSENSE

SGND

RUN

FCB

PLLFLTR

PLLIN

STBYMD

BOOST1

TG1

SW1

VIN

EXTVCC

INTVCC

BG1

PGND

BG2

SW2

TG2

BOOST2

LTC3780EG

10k

100Ω

220k

VOS+

15k

220k

487k

1% 8.25k

1000pF

100pF

47pF

VIN

0.1μF

100V

68pF

0.022μF

0.1μF

16V

2.2μF, 100V, TDK C4532X7R2A225MT

C1: SANYO 100ME100HC +T

C2, C3: SANYO 63ME220HC + T

D1: ON SEMI MMDL770T1G

D2: DIODES INC. 1N5819HW-7-F

D3, D4: DIODES INC. PDS560-13

D5: DIODES INC. MMBZ5230B-7-F

D6: DIODES INC. B1100-13-F

L1: SUMIDA CDEP147NP-100MC-125

R1, R2: VISHAY DALE WSL2512R0250FEA

0.1μF

16V

VBIAS

10μF

10V

1μF

16V

0.22μF

16V

10μH

2.2μF

100V

100μF

100V

VIN

36V TO 72V

1μF

16V

0.1μF

16V

VBIAS

SENSE+

SENSE–

VBIAS D2

VCC

GND

BOOST

TINP

BINP

LTC4444-5

TSBG

2.2μF

100V

C2,C3

220μF

63V

VOUT

48V

0.025Ω

44445 TA02a

SENSE+

SENSE–

D3 D4

0.025Ω

10Ω

10W

VOS+

10Ω

LOAD CURRENT (A)

EFFICIENCY (%)

21345

44445 TA02b

VIN = 36V

VIN = 48V

VIN = 72V

LTC4444-5

44445f

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

PACKAGE DESCRIPTION

MS8E Package

8-Lead Plastic MSOP, Exposed Die Pad

(Reference LTC DWG # 05-08-1662 Rev D)

MSOP (MS8E) 0307 REV D

0.53 ± 0.152

(.021 ± .006)

SEATING

PLANE

NOTE:

1. DIMENSIONS IN MILLIMETER/(INCH)

2. DRAWING NOT TO SCALE

3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.

MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX

0.18

(.007)

0.254

(.010)

1.10

(.043)

MAX

0.22 – 0.38

(.009 – .015)

TYP

0.86

(.034)

REF

0.65

(.0256)

BSC

0° – 6° TYP

DETAIL “A”

GAUGE PLANE

4.90 ± 0.152

(.193 ± .006)

BOTTOM VIEW OF

EXPOSED PAD OPTION

765

3.00 ± 0.102

(.118 ± .004)

(NOTE 3)

3.00 ± 0.102

(.118 ± .004)

(NOTE 4)

0.52

(.0205)

REF

1.83 ± 0.102

(.072 ± .004)

2.06 ± 0.102

(.081 ± .004)

5.23

(.206)

MIN

3.20 – 3.45

(.126 – .136)

2.083 ± 0.102

(.082 ± .004)

2.794 ± 0.102

(.110 ± .004)

0.889 ± 0.127

(.035 ± .005)

RECOMMENDED SOLDER PAD LAYOUT

0.42 ± 0.038

(.0165 ± .0015)

TYP

0.65

(.0256)

BSC

0.1016 ± 0.0508

(.004 ± .002)

LTC4444-5

44445f

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

LT 0508 • PRINTED IN USA

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No RSENSE is a trademark of Linear Technology Corporation.

TYPICAL APPLICATION

LTC3780 High Efﬁ ciency 8V-80V VIN to 12V/5A Buck-Boost DC/DC Converter

PGOOD

SENSE+

SENSE–

ITH

VOSENSE

SGND

RUN

FCB

PLLFLTR

PLLIN

STBYMD

BOOST1

TG1

SW1

VIN

EXTVCC

INTVCC

BG1

PGND

BG2

SW2

TG2

BOOST2

LTC3780EG

10k

100Ω

20k

100Ω

VOS+

220k

80.6k

113k

1% 8.06k

0.01μF

47pF

VIN

0.1μF

100pF

68pF

0.1μF

2.2μF, 100V, TDK C4532X7R2A225MT

100μF, 100V SANYO 100ME 100AX

C1: SANYO 16ME330WF

D1: DIODES INC. BAV19WS

D2: DIODES INC. 1N5819HW-7-F

D3: DIODES INC. B320A-13-F

D4: DIODES INC. MMBZ5230B-7-F

D5: DIODES INC. B1100-13-F

L1: SUMIDA CDEP147-8R0

0.1μF

16V

VBIAS

10μF

10V

TG1

SW1

1μF

16V

0.22μF

16V

0.22μF

16V

L1 8μH

2.2μF

100V

100μF

100V

VIN

8V TO 80V

1μF

16V

0.1μF

16V

VBIAS

SENSE+

SENSE–

VBIAS D2

TG1

VCC

GND

BOOST

TINP

BINP

LTC4444-5

TSBG

22μF

16V

330μF

VOUT

12V

10Ω

VOS+

4444 TA03

SENSE+

SENSE–

SW1

0.005Ω

10Ω