LTC1439 查看數據表（PDF） - Linear Technology

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LTC1439

Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators

Linear Technology 

LTC1438/LTC1439

directly to the collector of the external PNP pass device for

12V operation. When used as a comparator, this is the

noninverting input of a comparator whose inverting input

is tied to the internal 1.19V reference. See Auxiliary

Regulator Application section.

AUXON: Pulling this pin high turns on the auxiliary regu-

lator/comparator. The threshold is 1.19V. This is a conve-

nient linear power supply logic-controlled on/off input.

AUXDR: Open Drain Output of the Auxiliary Regulator/

Comparator. The base of an external PNP device is con-

nected to this pin when used as a linear regulator. An

external pull-up resistor is required for use as a compara-

tor. A voltage >9.5V on AUXDR causes the internal 12V

resistive divider to be connected in series with the AUXFB

pin.

W

FUNCTIONAL DIAGRA

PLLIN**

fIN

50k

CLP

COSC

RLP PLL LPF**

COSC

POR2

LBI

BATTERY

SENSE

LBO

PHASE

DETECTOR

2.4V

OSCILLATOR

POWER-ON

RESET

VFB2

1.11V

VSEC

AUXON**

VLDO

+

AUXDR**

AUXFB**

+

9V –

90.8k

10k

+

SFB1*

–

VIN 1µA

VIN

4.8V +

–

EXTVCC

SFB

1.19V

VREF

REF

5V LDO

REGULATOR

INTVCC

+

SGND

INTERNAL

SUPPLY

DUPLICATE FOR SECOND CONTROLLER CHANNEL

VIN

BOOST

INTVCC

DB

DROPOUT

DETECTOR

SQ

SFB

RQ

0.6V +

–

+

SHUTDOWN

SWITCH

LOGIC

I1

INTVCC

TGL

TGS**

SW

BG

PGND

–

8k

30k

180k

VFB

EA

gm = 1m

I2

4k

320k

61k

119k

INTVCC

SENSE –

SENSE +

VOSENSE*

VPROG*

CB

•

+•

CIN

COUT RSENSE

VOUT

CSEC

0V

3µA

6V

1.28V

1.19V

SHUTDOWN

RUN

SOFT START

DFB†

ITH

CC

RC

RUN/SS

CSS

*IN SOME VERSIONS, NOT AVAILABLE ON BOTH CHANNELS **NOT AVAILABLE ON LTC1438

†FOLDBACK CURRENT LIMITING OPTION

BOLD LINES INDICATE HIGH CURRENT PATHS

1438 FD

14389fb

9

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