Issue with setting TVL431A output voltage

crutschow

Joined Mar 14, 2008
30,818
Here's your circuit modified to operate properly.
R5 adds about 200mV of hysteresis so the circuit won't oscillate around the trip point.

upload_2019-5-18_0-27-39.png
 

crutschow

Joined Mar 14, 2008
30,818
Is this a voltage monitor circuit?
Yes.

To get better resolution in your simulation you need to reduce the value of the voltage steps in your .step command.
A step of 0.4V means the resolution of the circuit trip point is no more than that.

For this circuit, that has a switch point with hysteresis, it's probably better to vary the voltage with the pulse command, rather than use the .step command.
Another better alternate is the use the DC sweep command.
 

crutschow

Joined Mar 14, 2008
30,818
The current needs to stay above 80uA until the set regulator voltage is reached? The cathode current drops rapidly right when the set regulator voltage is reached.
When it reaches and drops below the set voltage, yes.
At that point the cathode current drops to ≤0.1μA.
 
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