P Channel Mosfet Vgs

Thread Starter

fastbike

Joined Dec 29, 2020
85
I've modelled the circuit (below) in LT Spice, which drives a single coil latching relay, and am happy that it toggles the relay depending on the two inputs at V1 and V2.

However I'm concerned that the P channel mosfet, Q1, will see 24V between Gate and Source when it is operating which is outside of the operating parameters.

If I substitute a device with Vgs of 25V such as FDN86265P, is this sufficient headroom to avoid operating issues ?


1668139346745.png
 

Thread Starter

fastbike

Joined Dec 29, 2020
85
I think I'm going to need another resistor between the gate of Q1 and the drain of Q2, to limit the voltage. As long as the gate threshold of Q1 is exceeded and the gate-source limit is respected I think this will work (at the cost of another small component)
 

Thread Starter

fastbike

Joined Dec 29, 2020
85
Answering my own question here. Resistor R4 now splits the gate voltage when Q2/Q3 are active so the Q1 gate sees -12v wrt the source, and 0v when Q2/Q3 are inactive

1668140958436.png
 
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