Datasheet

UCC28089
SLUS623A -- SEPTEMBER 2004 -- REVISED AUGUST 2006
12
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APPLICATION INFORMATION
If desired, the 60-Hz modified square wave inverter frequency could be programmed using an external sync
signal that might originate from a separate oscillator or digital controller. The following diagram in Figure 6 shows
a 50% duty cycle square wave fed into the CT pin, with a frequency of 120 Hz, and the resulting OUTA/OUTB
wave shapes.
3.3 V
OUT A
OUT B
Ext. Sync
DIS
SYNC
CT
CS
GND
OUTB
OUTA
VDD
UCC28089
1
2
3
4 5
6
7
8
Ext. Sync
U1
External Sync example with 50% duty cycle
NC
8.33 ms
16.7 ms
VDD
1 μF
Figure 6. External Synchronization Example with 50% Duty Cycle Square Wave
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DEVICE DESCRIPTION
UCC2540 High-Efficiency Secondary-Side Synchronous-Buck PWM Controller