GPIO Sinking Resistance

Question

I am powering an LED / current limiting resistor by sinking current into an IO pin. Where can I find the resistance of the IOs when sinking current?

RK · Accepted Answer

you don't say what drive strength you are using on the GPIO which is fairly important. If it's standard drive then it's as I wrote above, not GPIO resistance but current limitation, in fact 5mA is higher than the max in the spec sheet for SD. If it's HD then you're just below the minimum in the spec sheet but still possible. So again the likely reason for the voltage being higher than 0.4V is because the pins have current limiters. The only way a current limiter can work on a pin driven in the way you are driving them is to 'raise' the low voltage to the point the current falls to the clamped current limit.

GPIO Sinking Resistance

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