LM393: Amplifiers forum

There is no specified limit, but if the input is too slow, the output might indeed oscillate (because the switching noise or other noise might shift the voltage at the input).

All comparators used with slow signals should have hysteresis. Some devices have built-in hysteresis; with the LM393, you would need to add positive feedback. See, for example, Comparator with and without hysteresis circuit.

thanks Clemens for your support. hope that answers your question Masanori.