Kinetis Microcontrollers中的主题 Re: Applying voltage to GPIO pins on K22 device while unpowered

Applying voltage to GPIO pins on K22 device while unpowered

ryanmonfils — Fri, 01 Jul 2016 21:39:47 GMT

I generally try design hardware such that voltage is NOT applied to un-powered device pins, however I am unable to avoid it in this case. I know this question has been answered in other forums but not for the K22 device, specifically the K22FN1M0VLL12.

Is it OK to apply 3.3V to a GPIO pin through a 10K pull-up resistor when the rest of the device is not powered? The datasheet does talk about 5V tolerant pins but doesn't give a clear answer on my specific question.

Thanks!

Re: Applying voltage to GPIO pins on K22 device while unpowered

scottm — Sun, 03 Jul 2016 04:52:16 GMT

I didn't even realize that the K22FN1M0 had 5V tolerant inputs. Huh. I'd imagine it'd probably be OK then. With an ESD protection diode tied to Vdd you'd get something like 310 uA at 3.1v injected into Vdd, I think. Without one, you're probably fine. I'm pretty sure I've had that condition on some MK22FN1M0AVLH boards without any trouble.

I say hook up the I/O pin to 3.3v without any current limiting. If something goes pop and smells bad, then your answer is no. If it's still working fine the next day, then I think a few hundred uA isn't going to hurt it.

Maybe someone from NXP can give you a more definitive answer, but I'm an empiricist. :smileywink:

Scott

Re: Applying voltage to GPIO pins on K22 device while unpowered

jeremyzhou — Mon, 04 Jul 2016 03:07:27 GMT

Hi Scott,

It's Ok, however I'd still like to recommend to add an current limiting resistor, for instance 47K resistor just in case.

Hope it helps.
Have a great day,
Ping

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