Datasheet

8/16
Technical Note
Timing chart
(BD9781HFP)
- While in basic operation mode
-
While in overcurrent protection mode
FB
VIN
SW
EN/SYNC
Internal
OSC
Fig.27
Fig.28
External synchronizing function (BD9781HFP)
In order to activate the external synchronizing function, connect the frequency setting resistor to the RT pin and then input
a synchronizing signal to the EN/SYNC pin. As the synchronizing signal, input a pulse wave higher than a frequency determined
with the setting resistor (RT). On the BD9781HFP, design the frequency difference to be within 50%. Furthermore,
set the pulse wave duty between 10% and 90%.
Fig.29
F
SYNC
Internal
OSC
: For RT only
: For external
synchronization
Output short circuit
FB
SW
I
O
Internal
OSC
Auto reset Auto reset Auto reset Auto reset
2010.02 - Rev. B
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BD9778F, BD9778HFP, BD9001F, BD9781HFP