Re: P-channel MOSFET model

On Mon, 6 May 2024 01:58:15 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:

"John Larkin" <jjSNIPlarkin@highNONOlandtechnology.com> wrote in message
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On Sun, 5 May 2024 14:42:30 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
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"Edward Rawde" <invalid@invalid.invalid> wrote in message
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Does anyone know of a P-channel MOSFET, roughly equivalent to
XP233P1501TR-G which has a model I can use in LTSpice?
XP202A0003PR-G would be useful too.

>
Infineon BSS215P  might be more suitable for the FET.
That does have a simulation model.
http://www.infineon.com/dgdl/Infineon-SimulationModel_OptiMOS_PowerMOSFET_PSpice_20V_P-Channel-SM-v01_00-EN.zip?fileId=db3a30433d346a2d013d493ff9d160ab
I'll have to look into how compatible the model is with LTspice.
>
Microchip TC105 is also interesting but a bit pricey.
However it does lead to CD54NP as a possible choice for the inductor.
MA737 doesn't seem to be easily available but a suitable shottky diode
shouldn't be hard to find.
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Vishay SI2371EDS-T1-GE3 looks interesting too.
Not too pricey for lower on resistance.
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Some of the TI TPS5- series buck switchers are 19 cents.
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Your circuit looks like a good way to blow up transistors.
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Here's 12V to 5V 1A using the concept I had in mind of using a comparator
capacitively coupled to a FET.
Also using only components I could find in a fresh install of LTSpice.
If it doesn't work, fix the character encoding issue in the value of some
components.
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Don't worry it won't be going into production any time soon.

That works in simulation, but the hazard of ac coupling into the fet
gate is that it has a hangup state, the fet on hard forever and
nothing limiting the current but 12 volts into the load.


It also grunts at startup, fet full on until the +5 settles. That
could cave in a wimpy +12 supply, and it may never run right. The
diode will leak more than the fet gate, so the static default is fet
on. Just remove "startup" to see the hang state.

You could power a comparator from +12, dc couple into the gate, and
slow down the startup. Something like that. Using all discrete
transistors would be fun too.

You could just buy a switcher chip and copy the appnotes, as many
people do, but you wouldn't learn anything. I know a guy who started a
pretty cool company just copying eval boards, but then he started day
trading....

The Brat assigned me to do a giant Spice sim this weekend, a dual
isolated buck switching power supply that's in trouble, so I'm almost
Spiced out.

https://www.dropbox.com/scl/fi/kzzjdfijpacf2qlch2gyq/P941C_lores.jpg?rlkey=49mv67p1c0zvu9c5v5tdftk3f&raw=1

The sim is all analog, but the actual control loop will be digital, in
a small FPGA. One tricky part is that the two supples can be used
independently or in parallel, and the loads can be anything, with
remote sense.