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Smart Sync

C 1

220 F

o

m

C 2

o

220 F

m

C 2

22

i

0 F

m

C 1

33

i

0 F

m

R

SET1

R

SET2

PTH08T220W

INH/ UVLO

INH/ UVLO

+Sense

–Sense

GND

Track SYNC

TT

V Adj

O

V Adj

O

V 1

O

V 2

O

0

o

GND

PTH08T240W

+Sense

–Sense

GND

Track SYNC

TT

180

o

GND

Vcc

GND

Q

Q

PRE

CLR

CLK

D

SN74LVC2G74

PTH08T240W, PTH08T241W

SLTS264E – NOVEMBER 2005 – REVISED FEBRUARY 2007

Smart Sync is a feature that allows multiple power modules to be synchronized to a common frequency. Driving

the Smart Sync pins with an external oscillator set to the desired frequency, synchronizes all connected modules

to the selected frequency. The synchronization frequency can be higher or lower than the nominal switching

frequency of the modules within the range of 240 kHz to 400 kHz (see Electrical Specifications table for

frequency limits). Synchronizing modules powered from the same bus, eliminates beat frequencies reflected

back to the input supply, and also reduces EMI filtering requirements. Eliminating the low beat frequencies

(usually < 10 kHz) allows the EMI filter to be designed to attenuate only the synchronization frequency. Power

modules can also be synchronized out of phase to minimize source current loading and minimize input

capacitance requirements. Figure 25 shows a standard circuit with two modules syncronized 180

° out of phase

using a D flip-flop.

Figure 25. Smart Sync Schematic

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