LTC1439CG datasheet(23/32 Pages) LINER

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LTC1438/LTC1439

APPLICATIONS INFORMATION

RUN/SS1

SENSE+ 1

SENSE– 1

VPROG1

ITH1

POR2

COSC

SGND

LBI

LBO

SFB1

ITH2

VPROG2

VOSENSE2

SENSE– 2

SENSE+ 2

RUN/SS2

AUXDR

PLL LPF

PLLIN

BOOST 1

TGL1

SW1

TGS1

VIN

BG1

INTVCC

PGND

BG2

EXTVCC

TGS2

SW2

TGL2

BOOST 2

AUXON

AUXFB

LTC1439

DB1

DB2

CIN1

CIN2

COUT1

–

COUT2

RSENSE1

RSENSE2

CB1

0.1

µF

CLP

0.01

µF

CC1A

1000pF

RLP

10k

EXT

CLOCK

CB2

0.1

µF

GROUND PLANE

1438 F13

4.7

µF

RC1

10k

RC2

10k

VOUT1

–

VIN

VOUT2

1000pF

220pF

NOT ALL PINS CONNECTED FOR CLARITY

BOLD LINES INDICATE HIGH CURRENT PATHS

INTVCC

VIN

100k

1000pF

COSC

CC1B

220pF

CSS

0.1

µF

CC2B

470pF

CC2A

1000pF

CSS

0.1

µF

OUTPUT DIVIDER

REQUIRED WITH

VPROG OPEN

100pF

22pF

Ω

Figure 13. LTC1439 Physical Layout Diagram

PC Board Layout Checklist

When laying out the printed circuit board, the following

checklist should be used to ensure proper operation of the

LTC1438/LTC1439. These items are also illustrated graphi-

cally in the layout diagram of Figure 13. Check the follow-

ing in your layout:

1. Are the high current power ground current paths using

or running through any part of signal ground? The

LTC1438/LTC1438X/LTC1439 ICs have their sensitive

pins on one side of the package. These pins include the

signal ground for the reference, the oscillator input, the

voltage and current sensing for both controllers and the

low-battery/comparator input. The signal ground area

used on this side of the IC must return to the bottom

plates of all of the output capacitors. The high current

power loops formed by the input capacitors and the

ground returns to the sources of the bottom N-channel

MOSFETs, anodes of the Schottky diodes and (–) plates

of CIN, should be as short as possible and tied through

a low resistance path to the bottom plates of the output

capacitors for the ground return.

2. Do the LTC1438/LTC1439 SENSE– 1 and VOSENSE2 pins

connect to the (+) plates of COUT? In adjustable applica-

tions, the resistive divider R1/R2 must be connected

between the (+) plate of COUT and signal ground and the

HF decoupling capacitor should be as close as possible

to the LTC1438/LTC1439.

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