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Measuring LCL and OVP thresholds in LTSPICE

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Hi there!
I've been given a group of circuit schematics for testing and I must measure the current and voltage thresholds on a Latching Current Limiter and Overhead voltage Protector respectively. I know how to simulate and measure currents and voltages in LTSPICE but something about the behaviour of these circuits is overwhelming me... The simulations I've made are in attachment.
Thinking about the LCL I thought having a variable current source we could see to which current value the MOSFET stops working, so in the image lcl_12to3v3 that would be where both graphs cross for the first time (650mA), but for the 2nd case this no longer happens, Vs doesn't even go to 0, and the crossing graphs no longer applies... The difference between circuits is that first is from a rail to convert 12V to 3v3 and the second from 12V to 1V25. Can someone clarify me in this matter?

Thanks in advance
Gabriel Sá Pinto



Well-Known Member
Most Helpful Member
You sent pictures of your screen.
What will be real helpful is the spice files. (lil_3v3_Ith.ASC) Then we can run the same file and see what you see. (with out entering the data by hand and probably making a mistake)
Use the "Upload a File" button.


Active Member
how you know your R1 is correct for 1.25 1000mΩ vers. 180mΩ for 3.3 OR reduce your timestep
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Thanks for the replies, I don't know why but I didn't get any email notification that I got answers in this thread. Meanwhile I solved my issue. Thank you once again.
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