Power Rail Monitor Circuit

[ssashton]

Hi,

I would like to create a circuit that monitors a 48V power rail that feeds an audio amplifier. When the voltage begins to drop at power-off I want the circuit to pull the amplifier mute pin to ground.

I have thought up this circuit using a open drain comparator (output is connected to the mute pin with 10K pull-up) and made a Falstad sim. I would appreciate comments if my design seems sensible or there are any traps I might not have considered?

Note that the amp is powered directly from the 48V rail, but the comparator will be powered from a regulated 3.3V that comes off the 48V rail. I believe by the time the comparator looses power, the amplifier will not be operational as it appears to not start below about 18V.

[Benta]

Just use a MC33164-3 (onsemi) with a voltage divider at the input. Much simpler, and it's designed for the job. Or any other undervoltage detector. There are plenty out there.

[PGPG]

or there are any traps I might not have considered?

You divide 48V down to about 3V3.
Not all comparators powered by 3V3 will work with inputs being close to its supply voltage.

I agree that it is better to use IC destined to work as undervoltage detector.

[ssashton]

Thanks, I didn't know there were such simple ones. I had only seen pretty advanced power monitoring ICs.