PTQB425080 Datasheet, PDF (10/14 Pages) Texas Instruments – 200-W 48-V INPUT, 8-V OUTPUT, SEMI-REGULATED, ISOLATED DC-DC BUS CONVERTER

PTQB425080
SLTS269A – DECEMBER 2006 – REVISED JANUARY 2007
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Synchronizing Multiple POL Modules using SmartSync Clock Drive
The PTQB425080 provides a 275 kHz SmartSync clock signal that may be used to synchronize multiple
downstream non-isolated modules to a common frequency. Figure 10 shows a simplified block diagram of the
PTQB425080 clock signal driving the SmartSync input of two PTH08T220W modules. Synchronizing modules
powered from the same bus, eliminates beat frequencies reflected back to the input supply, and also reduces
EMI filtering requirements. These are the benefits of Smart Sync. Power modules can also be synchronized out
of phase to minimize source current loading and minimize input capacitance requirements. Figure 10 also shows
module U2 synchronized 180° out of phase with module U3 using an inverter circuit.
+V_I
+
C_I
100 µF
−V_I
SmartSync 5
1 +V_I
U1 ^{+VO 7}
PTQB425080N
2 _On/Off
3 _−VI
−V_O 4
f_CLK = 275 kHz
Inverter
V_O Bus (8 V)
+
C2
100 µF
1
U2
SmartSync
2
PTH08T220W
5
C3
470 µF
Inhibit GND V_OAdj
11
3,4
8
R2
1.21 kΩ
V_POL1
(3.3 V)
C4
470 µF
C5
470 µF
1
U3
SmartSync
2
PTH08T220W
5
Inhibit GND V_OAdj
11
3,4
8
R3
12.1 kΩ
V_POL2
(1.2 V)
C6
470 µF
Figure 10. Synchronizing Modules Powered from the Same Bus
UDG−06087
10
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