TLC372: TLC372 cannot distinguish two signal pulses with a difference of 10mV

Hi Lai,

Thanks for attaching a snapshot of your schematic.

A few notes/questions for you:

1. What is the input voltage of your signal you are measuring? What is the total swing you expect to see on your inputs?

2. What is your threshold set to (voltage at inverting pins)?

3. Do you have a scope shot of the comparator not being able to pick up the 10mV difference of your input signal?

4. I would recommend adding a filter to clean up any noise on your inverting pins. Where is the reference coming from? What is voltage you are dividing down from?

5. Generally adding caps directly on the output of the device is not recommended, as it will slew the output edges of the device.

Regards,

Jonny

Dear Jonny,

1. This is my signal, green ( to inverting pins of TLC372). 

2. Threshold set by UPWM and LPWM

Thanks,

Hải

Thanks Hai,

Do you have a scope shot of the threshold voltages seen at the non-inverting pins on the same screen as your input and output?

What is the value of the voltages that you are applying where the part is having issues distinguishing a 10mV difference? It's difficult to distinguish in your scope shot.

Thanks,

Jonny

Dear Jonny,

After reviewing the above diagram, I realized that it is only possible to distinguish signals below the lower threshold (LPWM), at the location of gate 1.

Don't know if my thinking is right?

Thanks,

Hai