Is there a way to detect 1ms pulse with voltage of around 300mV?

[KS]

We are already using ADC for battery sense, also tried using ADC and LPCOM but could not get any reliable result.

[Roger Clark]

I think the best solution is to use a transistor as an amplifier for this signal, and then use a normal GPIO input.

Assuming you simply want to detect that there is a pulse, and you dont want to measure its length, you can feed the signal via a capacitor to a forward biased transistor

Note. This will take some current all the time, but you can probably limit this by careful choice of bias resistor values, and perhaps use a FET rather than a bipolar transistor.

Edit. Note. This method would also have a small delay between the pulse arriving, and it being transferred though the capacitor.

[Hein]

Wouldn't 300mV be too low to activate a transistor or fet ? You would need a comparator or opamp ?

[Roger Clark]

You forward bias the base / gate voltage on the transistor to just below its switch on point, and the capacitor provides DC isolation, so that the bias voltage is maintained until the actual pulse arrives.

I've done a quick model of this in LTSpice and I can get it to work with a normal NPN transistor, but at the moment I get the GPIO triggerring on the trailing edge of the pulse.

I'm sure somebody who is skilled in analog design could easily design a single active component circuit to do better.

Of course the problem with this, is that you need to maintain the forward bias voltage and there would be leakage into the base of the bipolar transistor. Even so, my quick hack of a circuit was only taking 12uA

[Hein]

Ahh yes of course, should have paid more attention when reading your initial answer. That is a good solution.

[Roger Clark]

@kernels

No worries..