LT8551

1

Rev 0

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REG

POWER STAGE 1

REG

8551 TA01a

ISP

ISN

SENSE–

SENSE+

BOOST

TG

SW

BG

POWER STAGE 4

POWER STAGE 2

POWER STAGE 3

ENOUT

CLK1

TGSR TGSH

BGSH

TGSL

RUN PLLIN/MODE

LT8551

LTC3769

PINS FOR POWER

STAGES 2,3,4

LT8551 PINS NOT SHOWN

IN THIS CIRCUIT:

BST2, BST3, BST4, TG2, TG3, TG4,

SW2, SW3, SW4, BG2, BG3, BG4,

ISP2, ISP3, ISP4, ISN2, ISN3, ISN4

SYNC, PHS1, PHS2, PHS3, MODE,

TGBUF, BGBUF, CLK2, IAMPP, IAMPN,

SHDN, RT/MS, ILIM

5V TO 24V

24V/25A

REGSNS

BST1

SW1

ISN1

ISP1

BG1

TG1

REGIS

REGDRV

REG

GND

TYPICAL APPLICATION

FEATURES

DESCRIPTION

Multiphase Boost Converter

Expander with Internal Gate Drivers

The LT®8551 is a multiphase expander for synchronous

boost DC/DC converters. It operates in tandem with any

synchronous boost DC/DC converter to increase the load

current capability by adding additional phases, which are

clocked out-of-phase to reduce ripple current and filtering

capacitance. It easily adds phases without the need to

route sensitive feedback and control signals.

The LT8551 integrates 5V gate drivers and can support up

to four boost phases per device. Multiple LT8551 devices

can be used for up to 18 phases. It accurately monitors

and adjusts the current of each channel to achieve excel-

lent DC and transient current sharing.

The LT8551 operates over a fixed frequency from 100kHz

to 1MHz or can be synchronized to an external clock.

24V/25A Step-Up Expander System

APPLICATIONS

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Expands Up to 4 Phases per Chip

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Up to 80V Input or Output Voltage

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Cascade with Multiple Chips for High Current

Applications

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Supports Up to 18 Distinct Phases from 20° to 180°

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Phases Can Share Phase Angle

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Excellent DC and Transient Current Sharing

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Phase-Lockable Fixed Frequency 125kHz to 1MHz

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Supports Bidirectional Current Flow

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Eliminates the Need to Route Sensitive Feedback and

Control Signals.

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52-Lead (7mm × 8mm) QFN Package

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High Current Distributed Power Systems

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Telecom, Datacom, and Storage Systems

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Industrial and Automotive

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by U.S. patents, including 9077244.