LTC1628CG-SYNC Ver la hoja de datos (PDF) - Linear Technology

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LTC1628CG-SYNC

High Efficiency, 2-Phase Synchronous Step-Down Switching Regulator

Linear Technology 

W

FU CTIO AL DIAGRA

LTC1628-SYNC

PLLIN

FIN

50k

PLLFLTR

RLP

CLP

PGOOD

PHASE DET

DUPLICATE FOR SECOND

CONTROLLER CHANNEL

INTVCC

VIN

BOOST

DB

OSCILLATOR

CLK1

CLK2

0.86V

VOSENSE1

0.74V

0.86V

VOSENSE2

DROP

OUT

DET

SQ

RQ

BOT FCB

TOP ON

TG

TOP

SW

SWITCH

LOGIC

INTVCC

BG

BOT

0.55V

+B

–

SHDN

PGND

CB

+

D1

CIN

COUT

RSENSE

VSEC

3V

0.18µA

R6

FCB

R5

4.5V –

+

+

–

0.74V

BINH

FCB

3.3VOUT

0.8V

VREF

VIN

VIN

EXTVCC

INTVCC

+5V

SGND

4.8V +

–

5V

LDO

REG

INTERNAL

SUPPLY

I1

I2

–

– ++ –

+

0.86V

3mV

4(VFB)

SLOPE

COMP

45k

45k

2.4V

EA

OV

1.2µA

6V

SHDN

RST

4(VFB)

RUN

SOFT

START

INTVCC

30k SENSE+

30k SENSE–

VFB

0.80V

VOSENSE

0.86V

ITH

RUN/SS

DSEC

R2

R1

CC

CC2

RC

CSS

CSEC

VOUT

1628 FD/F02

Figure 2

U

OPERATIO (Refer to Functional Diagram)

Main Control Loop

The LTC1628-SYNC uses a constant frequency, current

mode step-down architecture with the two controller

channels operating 180 degrees out of phase. During

normal operation, each top MOSFET is turned on when the

clock for that channel sets the RS latch, and turned off

when the main current comparator, I1, resets the RS latch.

The peak inductor current at which I1 resets the RS latch

is controlled by the voltage on the ITH pin, which is the

output of each error amplifier EA. The VOSENSE pin receives

the voltage feedback signal, which is compared to the

internal reference voltage by the EA. When the load current

increases, it causes a slight decrease in VOSENSE relative to

the 0.8V reference, which in turn causes the ITH voltage to

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