PWM shape

[Vmax]

Anyone know the approximate shape of a PWM signal from a 28X1? Say at 5KHz (pulse width of 0.2ms), what would be a typical rise and fall time?

 

[hippy]

Somewhere around 22nS rise and fall time, although that depends on what it's actually connected to.

 

[Vmax]

Thanks Hippy.

That’s quick. On a 0.2ms timescale, a 22ns rise and fall time is not very noticeable. I have the PWM pin connected to a 200 ohms resistor, and then trough a 4N35 opto.

 

[womai]

Actually I measure something closer to 2ns rise/fall time (on a 20 GHz sampling scope). That is when going to an ohmic load. When you drive a long line and/or connect a (capacitive) input of another chip to it the rise time will be slower.

Wolfgang