Other Parts Discussed in Thread: LM5117,
Vramp exceeds 1.2V and reaches 1.76V, but it works normally. As shown in the figure, CH2 is the output voltage, CH3 is Vramp, which exceeds the OCP protection point.why can it work normally?
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Hello,
Is Vout regulated at correct value?
Can you share your schematic in pdf file?
Thanks
Qian
LM5119 use the same OC circuit as LM5117.
Based on information on LM5117 datasheet section 7.3.7, ON pulse will be terminated when emulated ramp signal reaches 1.2V.
I found one EVM and did some test. When RAMP pin voltage reaches around 1.3V, over current limit happens. The Vcs (cycle by cycle limit) range is from 106mV to 134mV. Considering the variation of current sense gain (typical gain is 10), 1.3V is in the range.
I have no idea why OC does not happen on your board when RAMP voltage is 1.7V.
Can you increase RAMP voltage further to see if OC will happen?