Open Drain max voltage

[DaPi_1514011]

Hi,

   

On a PRoC BLE, we can configure a GPIO in Open Drain, pulls low.  What is the maximum voltage we can put on the pin and sink?

   

E.g. if VCC is 1.8V, can we sink a 3.3V LED?  The electrical characteristics mentions one thing to do with GPIOs - a tolerance of +0.5V, and as a digital input I can see why that would be, but how about as an Open Drain?

   

Thanks, Dave

[HeLi_263931 · Accepted solution]

The voltage at any pins cannot be higher than Vcc. So no, you cannot switch a 3.3V load with an output when Vcc is only 1.8V.

   

The tolerances for the output come from the internal resistance of the output transistors - when you sink the maximum current through them they have a dropout voltage of 0.5V.

[DaPi_1514011]

ok, Thanks.

   

We decided this was the case and so have designed with this in mind.