TS391 will not pull output high with "low" input voltage

Thread Starter

punctualmanx375

Joined Jun 3, 2018
11
Hello,

I've been designing a voltage comparator to check battery voltage using LEDs.
This is the schematic:
1600285961139.png
The circuit works fine when powering it with 4V, but won't pull the output high (turn the LEDs off) when powering it with 3V.
Any suggestions or things I missed?
Thanks in advance!
 

AlbertHall

Joined Jun 4, 2014
10,418
The TS391 has a n open collector output so it can never drive the drive the output high. You provide a pull-up to bring the output high.
If I understand your circuit, one TS391 input is at 2V but what is the voltage on the other input when the circuit doesn't work?
 

Thread Starter

punctualmanx375

Joined Jun 3, 2018
11
I shoud've noticed that, weird that is does work at 4V though.
When I measure the zener voltage is ~2.18V (inverting input) and the non-inverting input is 3.4V.
 

Thread Starter

punctualmanx375

Joined Jun 3, 2018
11
Thanks, this really helped me out! I'll remember to pay more attention to these specs (this is my first time designing a comparator schematic).
 
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