protection.ov+rp.txt

15:58 <qyx> is this legit? https://i.stack.imgur.com/Ag4JL.png
15:58 <qyx> reverse polarity and OV protection
16:11 <fenugrec> qyx, bss84 max Vgs probably +-20V, so VIN>20V will kill it
16:22 <aandrew> qyx: that's what I use
16:22 <aandrew> that's out of an ST app note
16:22 <aandrew> er no, a cypress dev board
16:23 <aandrew> M1 and M3 need to be sized for full power, and the value of R1 is really dependent on the switching characteristics of M4 so you need to test across temperature
16:37 <karlp> what voltage do you choose for the zener?
16:37 <karlp> the exact overvoltage limit you want? or something else
16:41 <qyx> fenugrec: I know, thats only a generic circuit I found on interwebs
16:43 <qyx> aandrew: great
16:44 <qyx> I am not sure what happens if the voltage is increasing slowly under load
16:44 <qyx> M3 might not survive the linear region
16:46 <aandrew> karlp: well the idea is when the voltage across the zener reaches Vz it will start ot clamp and then the gate that it is connected to will start to turn on, causing the bigger mosfet to shut off
16:47 <aandrew> so you need select Vz and the resistors so that the mosfet starts to open up at the right voltage for you
16:56 <BrainDamage> zener off: Vs = Vin, Vg=Vin, Vs-Vg = 0 -> mos off, zener on: Vs = vin, Vg = Vz, Vs-Vg=Vin-Vz, if Vin-Vz>Vgs mos on, so the condition can also be written as Vin>Vgz+Vz


## parts for ideal diode shits
19:52 <englishman> whats a general purpose, cheap and available ideal diode or reverse current/voltage limiting IC for 2.8-5.2V, <100mA
19:52 <englishman> i feel like there should be a lot of these
19:53 <englishman> USB ORing basically with some shitty 2.8V source thrown in
19:53 <englishman> LM66100 lets see what that does
19:55 <englishman> hmm its one of those things that doesnt block reverse current when VIN is unpowered
19:56 <englishman> ooh yes it does
19:56 <englishman> nice
19:59 <englishman> Similar to the Dual Ideal Diode circuit, the Status Output can also be used to control a discrete P-Channel
19:59 <englishman> MOSFET
19:59 <englishman> oh this will simplify the rest of the circuit too
19:59 <englishman> nice
20:00 <englishman> pretty much cheaper than a diode and plenty in stock
20:34 <zyp> I looked at that, but went with the maxim one instead
20:34 <zyp> max40200
20:43 <zyp> but I don't do ORing, I do reverse current blocking
....
22:11 <qyx> englishman: lm66100
22:12 <qyx> and my new replacement for tps2595 efuse/hot swap controller is STEF05
22:13 <englishman> ty for independent confirmation that LM66100 is awesome