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LTC3732

3-Phase, 5-Bit VID, 600kHz, Synchronous Buck Switching Regulator Controller

Linear Technology 

LTC3732

3-Phase, 5-Bit VID,

600kHz, Synchronous Buck

Switching Regulator Controller

FEATURES

DESCRIPTIO

s 3-Phase Current Mode Controller with

Onboard MOSFET Drivers

s ±5% Output Current Matching Optimizes Thermal

Performance and Size of Inductors and MOSFETs

s 4.5V ≤ VCC ≤ 7V; 4.5V ≤ VIN ≤ 32V

s Differential Amplifier Accurately Senses VOUT

s Reduced Input and Output Capacitance

s Reduced Power Supply Induced Noise

s VID DAC Programmable from 1.1V to 1.85V

(VRM9.0/9.1)

s ±10% Power Good Output Indicator

s 250kHz to 600kHz Per Phase, PLL, Fixed Frequency

s PWM, Stage SheddingTM or Burst Mode® Operation

s OPTI-LOOP® Compensation Minimizes COUT

s Adjustable Soft-Start Current Ramping

s Short-Circuit Shutdown Timer with Defeat Option

s Overvoltage Soft Latch

s Small 36-Lead Narrow (0.209") SSOP Package

s QFN 5mm × 7mmU38-Lead Package

APPLICATIO S

s Desktop Computers

s High Performance Notebook Computers

s High Output Current DC/DC Power Supplies

The LTC®3732 is a PolyPhase® synchronous step-down

switching regulator controller that drives all N-channel

external power MOSFET stages in a phase-lockable fixed

frequency architecture. The 3-phase controller drives its

output stages with 120° phase separation at frequencies

of up to 600kHz per phase to minimize the RMS current

losses in both the input and output filter capacitors. The 3-

phase technique effectively triples the fundamental fre-

quency, improving transient response while operating

each controller at an optimal frequency for high efficiency

and ease of thermal design. Light load efficiency is opti-

mized by using a choice of output Stage Shedding or Burst

Mode technology.

A differential amplifier provides true remote sensing of both

the high and low side of the output voltage at load points.

Soft-start and a defeatable, timed short-circuit shutdown

protect the MOSFETs and the load. A foldback current

circuit also provides protection for the external MOSFETs

under short-circuit or overload conditions.

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

Burst Mode, OPTI-LOOP and PolyPhase are registered trademarks of Linear Technology

Corporation. Stage Shedding is a trademark of Linear Technology Corporation

TYPICAL APPLICATIO

VCC

4.5V TO 7V

10µF

0.1µF

SW3 SW2 SW1

POWER GOOD INDICATOR

OPTIONAL SYNC IN

5 VID BITS

680pF

5k

0.1µF

100pF

VCC

TG1

LTC3732 SW1

BOOST1

BOOST2

BG1

BOOST3

SENSE1+

SENSE1–

PGOOD

PLLIN

PLLFLTR

VID0-VID4

ITH

RUN/SS

SGND

EAIN

IN–

IN+

TG2

SW2

BG2

PGND

SENSE2+

SENSE2–

TG3

SW3

BG3

SENSE3+

SENSE3–

1µH

0.003Ω

VIN

+

5V TO 28V

22µF

35V

VIN

1µH

0.003Ω

VOUT

1.1V TO 1.85V

55A

VIN

1µH

0.003Ω

+ COUT

470µF

4V

3732 F01

Figure 1. High Current Triple Phase Step-Down Converter

3732f

1

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