Current capability of DIO on EEBoard

[CharlesS]

Hello,

On Digilent's EEBoard, what is the max safe sink/source current for any one digital I/O pin/channel?

 

An internet search, and parsing the Spartan 3 datasheet, suggest 8mA per pad/pin. If so, that's really unfortunate; I'd rather not have to buffer this 10~15mA IR LED if I can avoid it.

 

-Charlie

[attila]

Hello,

 

This should work with Electronics Explorer because the digital IO pins are configured to 16mA drive and have 220Ω PTC thermistor. 

[CharlesS]

Oh, cool.

That also happens to explain why my LED is a bit dim. I was thinking I was maybe overloading the pin, and thus, seeing a voltage drop off the sourcing p-FET. But I guess I just needed to account for the PTC resistance in my LED current calculations; that's excellent.

I was actually a bit upset because it looked like the EEboard didn't have any protection for the DIO, but all those ~0603 resistors in a row are actually polly fuses eh? ... Good to know. Though, I think I still would have preferred socketed buffer IC's myself.

In any case, thanks for the info.
-Charlie

[attila]

Yes, the PRG18BB221 PTCs are those 37 in a row.

In case the current is not enough you could use two or more digital IOs to drive your circuit.