AM335x with pullups on external power

Gerard Belanger1

I am working with a BeagleBone/Cape style design. I have a power supply on my Cape to generate +5 and +3.3
for local hardware. I am feeding the local +5 to the BeagleBone to provide it's power.
My concern is that I have to put some pullups on some I/O pins to prevent my hardware from doing bad
things until the processor initializes the I/O.
Since the power on the Cape will be powering the BeagleBone,
the pullups and some of the Cape signals to the BeagleBone will be present before it powers up.
Does this present a problem to the i/o pins on the AM335x?

Gerry Belanger

over 13 years ago

0 peaves over 13 years ago

TI__Guru 63875 points

You must not violate the "Steady State Max. Voltage at all IO pins" requirement of "-0.5V to IO supply voltage + 0.3 V"which can be found in the Absolute Maximum Ratings section of the AM335x Data Sheet. Therefore you should not apply pull-ups before the respective supply voltage.

Regards,
Paul

0 Gerard Belanger1 over 13 years ago in reply to peaves

Intellectual 955 points

Thanks Paul.

I thought that might be the case. Easy enough to do at this stage.

GerryB

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AM335x with pullups on external power