Datasheet

Smart Sync
C 1
220 F
o
m
C 2
o
220 Fm
C 2
22
i
0 Fm
C 1
33
i
0 Fm
R
SET1
R
SET2
PTH08T220W
V
I
V
I
V
O
V
O
INH/ UVLO
INH/ UVLO
+Sense
–Sense
GND
Track SYNC TT
V Adj
O
V Adj
O
V 1
O
V 2
O
V
I
= 5 V
0
o
GND
PTH08T240W
+Sense
–Sense
GND
Track SYNC TT
180
o
GND
Vcc
GND
Q
Q
PRE
CLR
CLK
D
f
clock
= 2 Xf
modules
SN74LVC2G74
PTH08T240W , PTH08T241W
SLTS264J NOVEMBER 2005 REVISED JUNE 2009 ...................................................................................................................................................
www.ti.com
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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