TDA8380A Datasheet, PDF (7/20 Pages) NXP Semiconductors – Control circuit for switched mode power supplies

Philips Semiconductors
Control circuit for switched mode power supplies
Product specification
TDA8380A
Synchronization
The synchronisation input (pin 11) can be driven by either an optocoupler or a loosely coupled pulse transformer.
Figure 5 illustrates synchronization using the 0.85 V threshold and a digital signal connected to the SYNC input (for
example, an optocoupler between pin 11 and V_CC); the duty factor of the pulse is not very important. The oscillator starts
at the first negative going edge of the sync. signal after the low voltage level has been reached. The synchronization
frequency must be lower than the free running frequency. Synchronization must never affect the period time as this will
corrupt the setting of the maximum duty factor.
Fig.5 DC coupled synchronization using the 0.85 V level.
In Fig.6 the disabling threshold (5.6 V) is used for synchronization. In this case the oscillator starts at the positive going
edge of the sync. signal.
November 1993
Fig.6 DC coupled synchronization using the 5.6 V level.
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