Brooke Clarke wrote:

> I'm trying to compare the Source and Sink capabilities of the I/O pins 
> on the 16F876() and 16F916.
> I can find in the data sheet that they are both specified for sourcing 
> or sinking 25 ma max but can not find the internal resistance for source 
> and sink modes.  Is that info available?

I've never seen it spec'ed. What gives you a hint are the Vol and Voh specs
(here I'm using D080 and D090 of the 16F690).

With a current of 8.5mA, you're guaranteed a voltage <600mV. Assuming a
voltage of 0mV at 0mA, that means that the internal sink resistance
<600/8.5 Ohms = 70 Ohms. (If the voltage is >0mV at 0mA, the internal
resistance becomes smaller, so this is the worst case.)

Similarly with the sourcing case: at 3mA, you have a difference <700mV.
Again assuming a diff of 0mV at 0mA, that's then <700/3 Ohms = 230 Ohms
(worst case).

Both are probably not actually linear resistors over the full output
current range, with the sinking driver probably being more linear
(predictable) than the sourcing driver over the full 25mA range.

Gerhard

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