Smart Sync

PTH04T240F

V

I

C

I2

220 mF

R

SET2

Track

GND

VoAdj

TT

+Sense

-Sense

Inhibit/

UVLO

C

O2

1000 mF

GND

CLR

D

Q

PRE

V

PTH08T220W

V

I

C

I1

330 mF

Track

GND

V

V

O

TT

+Sense

-Sense

+

Inhibit/

UVLO

C

O1

220 mF

Sync

+

+

Q

CLK

V

CC

SN74LVC2G74

0°

180°

+

SYNC

UDG-08164

f

R

SET1

V

O

V

O1

V

O2

GND

GND

PTH04T240F

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

synchronization 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 21 shows a standard circuit with two modules syncronized 180°

out of phase using a D flip-flop.

Figure 21. Smart Sync Schematic

22

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