We’ve been doing some tests on above, and get considerable oscillation on output when i/p risetime is 100us or so. Please see attached screenshot: yellow trace is i/p signal, 4.9v p-p, risetime of 100us (ignore Y axis scale for signal – x10 probe attached). Blue trace is o/p signal – as you can see, any amount of noise on i/p is giving rise to multiple o/p transients.
Is there any form of hysteresis on the input? The datasheet implies it’s Schmitt but it doesn’t act like it. Is there a pin for pin compatible device which does have Schmitt inputs?