BD9D321EFJ Datasheet, PDF (13/28 Pages) Rohm – 4.5V to 18V Input, 3.0A Integrated MOSFET 1ch Synchronous Buck DC/DC Converter

BD9D321EFJ
Datasheet
2 Protective Functions
The protective circuits are intended for prevention of damage caused by unexpected accidents. Do not use them
for continuous protective operation.
2-1 Over Current Protection (OCP)
Over current protection function is effective by controlling current which flows in low side MOSFET by 1 cycle each of
switching period. With inductor current exceeding the current restriction setting value I_OCP when LG is ON, the HG
pulse cannot be hit even with FB voltage under REF voltage and LG continues to be ON until it is below I_OCP. It hits
HG when it goes below I_OCP. As a result both frequency and duty fluctuates and output voltage may decrease.
In a case where output is decreased because of OCP, output may rise after OCP is released due to the action at high
speed load response. This is non-latch protection and after over current situation is released the output voltage will
recover.
V_OUT
FB
High side
MOSFET gate
(HG)
Low side
MOSFET gate
(LG)
OCP threshold (Iocp)
Inductor current
OCP signal
inside IC
Output load
current
Normal
Over
Current
Normal
Figure 26. Over current protection timing chart
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TSZ22111•15•001
13/25
TSZ02201-0J3J0AC00490-1-2
07.Aug.2013 Rev.001