LM5119: LM5119：OCP

Hi,

As you said,Vramp refer to RAMP pin voltage.

My understanding is that when the sum of Vramp and the voltage whitch ten times of between CS and CSG pins more than 1.2V, protection starts, but Vramp exceeds 1.7V, the circuit still works normally, how to understand?

Thanks

Hello,

I'm looking forward to receiving your reply~

Thanks

Hello, 

Is Vout regulated at correct value?

Can you share your schematic in pdf file?

Thanks

Qian

Hello,

The output voltage is correct;

I am sorry that the schematic is not convenient to share.

My question is that the OVP logic of the chip seems to conflict with DS.How to understand this situation?

Thanks

Hello, 

Can you let me know Vin, Vout, Ramp and Camp?

Thanks

Qian

Hello,

I just want to confirm the OCP conditions，please answer me directly.

OCP is triggered when the sum of VRAMP and VCS is greater than 1.2V, yes or no? Where VRAMP represents the voltage of the RAMP pin,VCS represents 10 times the voltage across the sampling resistor.As shown below:

Thanks

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?

Btw, I will send you a private message with my email address. 

If you can provide your schematic by email. I can check if the problem is related to schematic.