Hi all,
I am trying to realize a low power voltage monitor with hysteresis.
I have a battery or capacitor, and I want to monitor its charge using a comparator (TLC3702). I set 2 thresholds for the comparator so that I have a hysterical type of comparator. The output of the comparator drives a solid state SPST relay (CPC1114N).
The tricky thing is that from the battery I derive and keep independently 3 things:
1) the supply of the comparator Vs
2) the reference voltage of the comparator Vref, that creates the 2 thresholds (voltage divider R4-R5)
3) the voltage across the battery that I want to monitor Vin, I scale it with the voltage divider R6-R7 so that I can compare it with Vref as I need.
To generate a Vsupply (Vs) and the Vref both at 2.5V, but keeping them independently, I use two LM285LPE 3-2-5 (
http://www.ti.com/lit/ds/symlink/lm285-2.5.pdf).
Functionally this works and it does what it is supposed to do.
Now, my problem is the power consumption of the whole circuit, I mean the current drawn from the battery. The comparator TLC3702 is supposed to draw current in the order of micro-amps. But my whole circuit nabsorbs 3-4 mA. I don't know which component is absorbing that much.
I thought it was the switch but very little changes if I remove it