TL331: Schematic review and recommendation

It s indeed recommended to have some hysteresis. It should be larger than the expected noise.

The TL331 does not have rail-to-rail inputs; it does not work correctly when both inputs are above 1.3 V. Use a device with rail-to-rail inputs like the TL331LV, or a comparator with built-in hysteresis like the TLV7021.

Hi Gary,

Thanks for reaching out. 

Please see some of our materials on desiging for hysteresis: 

Non-inverting comparator with hysteresis circuit (Rev. A)

Inverting comparator with hysteresis circuit (Rev. A)

AS Clemens mentions, how much to add depends on how much noise you expect, but generally we recommend to add hysteresis.

For low voltage operating systems such as 3.3V, we recommend TL331LV as it is rail to rail and would be suited for this application as it is a drop in replacement.