pull-ups for Spartan3

Hi,

for my Spartan3, being the internal pull-ups only good for non connected pins, which external pull-ups should I place on my output pins (that go into output buffer, opto and bjt before reaching the output pin of the board), 10kOhm, 4.7kOhm?

Thanks, Marco

Reply to
Marco
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Who told you that the internal pullups are only good for unconnected pins?

Are you using these outputs as open collector? If they are driving a BJT, why do you need a pullup at all? Just drive through a series resistor to limit the current. Or you can remove the BJT and drive the opto directly. Spartan3 will drive up to 24 ma, no?

Reply to
rickman

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