# problem in low battery detector circuit

#### Sudip Mandal 2

Joined Mar 29, 2017
32
I have designed a low battery detector circuit using low power comparator MCP6541 for a 4.2V Li-ion battery. This circuit checks whether the battery voltage if the battery voltage is lower than 3.5V then it will glow LED. Check the circuit below.

The circuit is working properly but the problem is led is flickering when it is glowing because the battery voltage is not constant it is fluctuating withing 0V- to 0.2V band as per load on the battery. when the battery voltage coming to reference voltage 3.5V due to fluctuation batter voltage sometimes goes below 3.5V sometimes above 3.5V so the led also flickering accordingly.
What I am thinking to put a capacitor across the R4 to minimize the fluctuation but still there chance to flickering. Please suggest me the best way to avoid flickering of LED.

#### crutschow

Joined Mar 14, 2008
26,058
Connect a resistor from the output pin to the Vin+ pin to provide some hysteresis in the trip point.
The resistor value depends upon the value of R3 and R4.
You probably want a value to give a hysteresis of about 50-100mV.

Last edited:

#### TeeKay6

Joined Apr 20, 2019
572
Connect a resistor from the output pin to the Vin+ pin to provide some hysteresis in the trip point.
The resistor value depends upon the value of R3 and R4.
You probably want a value to give a hysteresis of about 50-100mV.
I think you meant to say that the feedback resistor depends upon the value of R5 & R6, not R3 & R4. The label "+" at pin3 of IC2 is not clear, but the datasheet confirms that pin3 is the non-inverting input.

#### crutschow

Joined Mar 14, 2008
26,058
I think you meant to say that the feedback resistor depends upon the value of R5 & R6
Yes, I did.
Thanks for catching that.

Last edited:

#### Bordodynov

Joined May 20, 2015
2,745
See

#### Attachments

• 1.6 KB Views: 6