e2545: GPIO: PTB[0:11], PTB[16:23], PTC[0:19], and PTD[0:7] are not 5 V tolerant

[gigglerg]

Ref: e2545: GPIO: PTB[0:11], PTB[16:23], PTC[0:19], and PTD[0:7] are not 5 V tolerant.

I am using a K60 variant and the circuit is already prototyped.  I am worried as some 5v logic is connected to portb i/o that I am presently testing and this errata was not known about before the h/w guys produced my test board.

What the errata does not say is what happens when you do drive an pio input with 5v?  will it die?  produce undetermined results when reading pin registers?  how about the alternative peripherals attached to pins?

Please Freescale since the part was supposed to be 5V tolerant some further explanation is required.  I do feel you should update your datasheet so it's absolutely obvious when selecting parts rather than leave it tucked away in an errata.

Regards,

dc

[egoodii]

I would simply suggest you avoid the issue by using 'newer' silicon without this errata.  While you may be able to 'survive' some pins hitting the protection diodes, chips also have an 'overall sum of injected currents' limit you don't want to hit, either for the survival of the chip OR from an overall over-drive of your VDD regulation.

[Paul_Tian]

Hi, DC

The risk of non-5V tolerant pin is the current will flow to VDD when pin voltage is higher than VDD. If you add 5V to a non-5V tolerate pin, we will have the risk to damage system VDD.

Hope my reply can help you.

Best Regards

Paul

[erikmalund]

The only things guaranteed are death and taxes.  However I will suggest/surmise that weakly driving a non-tolerant input would just result in a bit of current running in the parasitic diode. I recall an incident when this was the case and the %V signal came from an external device.  The result was that you could not turn the uC off, when you did Vdd was supplied from the external device through the parasitic diode.

I guess that you, like most, will run your prototype and find out you need a respin of the board. I would not be too worried about running your prototype as is, but would, for the respin add some level conversion/protection.

Erik