LTC7820 Demo Circuit Voltage Doubler LTSpice fails before 2X Voltage

Hi Eric49 ,

Does it make sense for the example circuit to never reach regulation? Maybe?? To show slew rate protection? Still seems off. With the 3.4Ω load, the current sense resistor has spikes that top out at >-160A or so, seemingly pulled by the C16 and C3 caps. Not sure if those spikes are expected. The 4Ω version does not reach that level. Also not an expert.

mike (LTspice Team)

Hi Mike, 

I am learning and debugging at the same time. Although the comments on the top of the page show the input range is 6V-36V, the Vi used was 12.0V, and the Rload was 3.4 Ohms. Therefore, I expected it to work with (at least) those values. I was trying to troubleshoot what was tripping the failure - hysteresis, I-Sense, UV, thermal, filtering on Vhigh- and Vlow-sense, etc. It is a slow process to separate those possibilities without distinct indicators. I will continue doing so.

I found Design Note 571 on the voltage doubler. That schematic was said to provide 24V @ 7A, with 12V input. I added a 3.243 Ohm load for 7A out, and this circuit worked. There were numerous parameter changes from the "LTSpice Demo Circuit", but the significant change was the Frequency resistor at 68K in DN 571, and 100K in the Demo Circuit simulation. I changed the 68K to 100K in the DN 571 circuit and it failed at 20.5V out. 

So, I am still learning about the RMS currents in various components, versus various Vin and Rload conditions, but my original comment remains that a provided circuit should work with the parameters given.