LTC3707IGN datasheet(27/32 Pages) LINER

27 / 32 page

LTC3707

3707fb

APPLICATIONS INFORMATION

PC Board Layout Checklist

When laying out the printed circuit board, the following

checklist should be used to ensure proper operation of the

LTC3707. These items are also illustrated graphically in

the layout diagram of Figure 10. The Figure 11 illustrates

the current waveforms present in the various branches

of the 2-phase synchronous regulators operating in the

continuous mode. Check the following in your layout:

1. Are the top N-channel MOSFETs M1 and M3 located

within 1cm of each other with a common drain connection

at CIN? Do not attempt to split the input decoupling for

the two channels as it can cause a large resonant loop.

2. Are the signal and power grounds kept separate? The

combined LTC3707 signal ground pin and the ground return

of CINTVCCmust return to the combined COUT(–) terminals.

The path formed by the top N-channel MOSFET, Schottky

diode and the CIN capacitor should have short leads and

PC trace lengths. The output capacitor (–) terminals should

be connected as close as possible to the (–) terminals

of the input capacitor by placing the capacitors next to

each other and away from the Schottky loop described

above.

3. Do the LTC3707 VOSENSE pins resistive dividers connect

to the (+) terminals of COUT? The resistive divider must

be connected between the (+) terminal of COUT and signal

ground and a small VOSENSE decoupling capacitor should

be as close as possible to the LTC3707 SGND pin. The R2

and R4 connections should not be along the high current

input feeds from the input capacitor(s).

CB2

CB1

RPU

PGOOD

VPULL-UP

(<7V)

CINTVCC

CIN

CVIN

VIN

RIN

INTVCC

3.3V

RUN/SS1

SENSE1+

SENSE1–

VOSENSE1

FREQSET

STBYMD

FCB

ITH1

SGND

3.3VOUT

ITH2

VOSENSE2

SENSE2–

SENSE2+

PGOOD

TG1

SW1

BOOST1

VIN

BG1

EXTVCC

INTVCC

PGND

BG2

BOOST2

SW2

TG2

RUN/SS2

LTC3707

COUT1

VOUT1

GND

VOUT2

3707 F10

COUT2

RSENSE

Figure 10. LTC3707 Recommended Printed Circuit Layout Diagram

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