LTC3728LXC(RevA) 查看數據表（PDF） - Linear Technology

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LTC3728LXC
(Rev.:RevA)

Dual, 550kHz, 2-Phase Synchronous Regulators

Linear Technology 

W

FU CTIO AL DIAGRA

LTC3728L/LTC3728LX

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

INTVCC

3V

0.18µA

R6

FCB

R5

4.5V –

+

+

–

0.74V

BINH

FCB

3.3VOUT

0.8V

VREF

VIN

VIN

EXTVCC

4.8V +

–

INTVCC

+5V

SGND (UH PACKAGE PAD)

5V

LDO

REG

INTERNAL

SUPPLY

I1

I2

–

– ++ –

+

0.86V

3mV

4(VFB)

SLOPE

COMP

45k

45k

2.4V

EA

OV

INTVCC

30k SENSE+

30k SENSE–

VFB

0.80V

VOSENSE

1.2µA

6V

0.86V

SHDN

RST

4(VFB)

RUN

SOFT

START

ITH

RUN/SS

R2

R1

CC

CC2

RC

CSS

VOUT

3728 FD/F02

Figure 2

U

OPERATIO (Refer to Functional Diagram)

Main Control Loop

The IC uses a constant frequency, current mode step-

down architecture with the two controller channels oper-

ating 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 con-

trolled 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 in-

creases, it causes a slight decrease in VOSENSE relative to

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

3728lxfa

9

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