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Raspberry Pi GPIO pin max current

fustini

I became curious recently about the max current per pin on the Pi.  I thought I might share some of the helpful references I found.  I read this discussion on the Foundation's forum:

 

http://www.raspberrypi.org/phpBB3//viewtopic.php?f=44&t=12498

 

Two great references were linked from that thread: 

 

GPIO pads control

http://www.scribd.com/doc/101830961/GPIO-Pads-Control2

documentation by Gert which concludes:

all the electronics of the pads are designed for 16mA.

 

Understanding Output

http://www.thebox.myzen.co.uk/Raspberry/Understanding_Outputs.html

Explains relationship between voltage, current and impedence.  It summarizes:

A maximum of 16mA per pin with the total current from all pins not exceeding 51mA.

 

Further explanation:

When the Pi was designed, they used a figure of 3mA per GPIO pins in determining if the regulator could supply enough current. Hence the simple 3mA limit mentioned before. However, if not all the pins are supplying current then you can divert those pin’s share of the current into the ones you are using. Hence the total recommended current limit of 17 * 3 = 51mA.

 

BTW, I noticed that Gert has posted other useful Pi technical documents on Scribd:

http://www.scribd.com/gvanloo8080

  • Those links were very good reading, thanks for that, Drew!  The precise info is very useful.

     

    PS. Enable every single Javascript source on Scribd or the documents seems to omit all kinds of info.  In fact I'm not even sure I'm seeing it all, as some of the articles end rather abruptly.  That site has always given my browsers on all my machines trouble of one kind or another, and completely blank pages or hung access there aren't uncommon for me.

  • in reply to morgaine

    Yeah, I found it annoying you seem to have to pay for a premium account to download the PDF.  Kinda wish those documents from Gert were published somewhere else (maybe I just don't know).  Anyways, good technical info straight from the source.