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Unread 10-03-2015, 17:38
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Re: Maximum current draw through DIO port

http://dangerousprototypes.com/2011/...reshold-chart/
http://www.pericom.com/assets/App-Note-Files/AN066.pdf

74HCTxxx or 74LSxxx TTL logic chips ought to be able to tolerate 3.3V inputs.

Just remember to put a voltage divider on outputs to DIO inputs to go from 5V TTL supply voltage to 3.3V.

In this way with a 74HCT240 (inverting) or 241 (non-inverting) octal buffers give you 8 buffers per chip.

These buffers are usually capable of >25mA of sink/source current.

With that one could drive the inputs of the ULN2803 that would give you 8 Darlington transistors good for 500mA up to 50V.

Not sure what you can do with that but I would advise checking the rules carefully.

Last edited by techhelpbb : 10-03-2015 at 17:57.