LTC7862 Current Limit Level

There are a couple of things to take into account.  The previous query mentions the ripple current which is in the datasheet equation and if you are trying to recreate the sensing circuit from DC2674A, take into account the potential divider R8 and R21 that makes the 4 milliohm shunt look more like 3.2 milliohms.  When I simulated this, the Vsense was around 45 mV - a little low but within the datasheet parameters and the current limited at 14A as predicted.

I understood what you said with potential divider Walker, thanks. 

But please check simulation which I attached. 

Why 7862 limiting the current at 32mV in my simulation ? Please measure diff sense+ and sense- voltage. It detects a fault condition. 

It was a quick design, sorry if I missed something important. 

7862_sim.asc

There's a lot of output capacitance (5 milli-farad) in the design, so you can see it takes a long time for the output to change.  Between 10ms and 16ms, when the input goes from 16V to 80V, you can see the part limiting the current at the 55A setpoint with a Vsense of around 45mV.  So I believe that the model is functioning as intended.  When the output voltage eventually gets to the clamp point of 41.6V you can see some instability, no doubt caused by the highly capacitive load.  Beyond that point, the current drops and the Vsense will also drop (as it is a scaled version of the current), meaning the part is not in current limit anymore.

I totaly agree with you for all topics which you mentioned above. After 10ms, part works very well but before 10ms, why it limits the current around 32mV ?

My expectation from 7862 is ; at 0ms, it will start to charge the output capacitance with the current limit ( 50mV) and when it sets the output at 16V(input voltage, ignored the rdson of mosfets and losses) 7862 will act in pass through mode. Could you please explain this ? 

I also agree with instability at 41.6V. I need the change some values on the design. 

Any comment ? 

Hi KAYDIN556,

Good day to you.

Same with the response in another EngineerZone forum discussion (link below),

ez.analog.com/.../385972

with regards to the LTC7862 current threshold, the issue has already got the attention of the LTspice team.
A model update is already on its way.
An internal process just needs to be completed before the updated model will be made available in the LTspice library.

Please perform a Sync Release to update your LTspice library in a week or two.
We will also monitor the progress of this until your concern on this particular issue in LTC7862 is resolved.

Thank you.

Dear John,

Thank you for your support. I will check the situation in a week or two.

Best wishes.

Hi KAYDIN556,

An updated LTC7862 model is now available in LTspice library.
Please perform a Sync Release to update your library.

Here's a basic test I did. It shows that the Vsense max is set at 50mV.

Hi KAYDIN556,

An updated LTC7862 model is now available in LTspice library.
Please perform a Sync Release to update your library.

Here's a basic test I did. It shows that the Vsense max is set at 50mV.