Re: MSP430F2012 - analog voltage at IO/ADC pin while device is unpowered
Without Vcc, it is not a good idea to have any signal on any pin.
--- In m..., Aaron Greer wrote:
> I've come across a strange behavior in my current design.
> Under certain conditions the MSP430 is un-powered, but there is an
analog signal on one or more IO/ADC pins. I can measure a current
(5-10uA) entering the MSP430 pin and apparently leaving the VCC pin.
One explanation I can think of is that the internal ESD protection
devices are forward biased and conducting out the VCC pin. The other
part of the story is that after the MSP experiences this condition, I
begin to see unexpected behavior (with the device powered) on the
IO/ADC pins which had the analog voltages present. For instance, the
internal pull up or pull down resistors seem to be enabled (which one
seems random), when I'm certain I've disabled them in my application
code. Can you please provide some insight regarding any adverse
affects of powering the IO/ADC pins with the MSP un-powered? Do you
think there may be a problem with this that is causing the strange
pull up/down behavior? Do you expect doing this would decrease the
lifespan of the MSP devices?