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Author Topic: SS MPG output current?  (Read 3747 times)

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SS MPG output current?
« on: July 11, 2008, 02:11:53 PM »
Hi Guys,

I was about to hook up my MPG to the SS,  I measured the current of the MPG it was a little over 50ma,  I got worried and wondered what the output current for the SS MPG 5Volt supply is?  In the SS manual, I saw a 32ma limit for the sourcing and sinking of input and output pins, but I am unclear on the board supplied current for the MPG.  Thanks for the help,
Does anyone know what it is rated for?
Jim C.

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Re: SS MPG output current?
« Reply #1 on: July 11, 2008, 09:02:24 PM »
I have left a message for Greg but he isn't in right now. Have you looked on the SS forum for answers? I think I saw it there once, but can't be certain.


Try a search and also on the home page, documentation.

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Re: SS MPG output current?
« Reply #2 on: July 11, 2008, 10:00:19 PM »
Thanks Brett for contacting me.  The SS's 5V output is not very limited.  There is a ferrite that is in line and it is a 4A device I think.  But I really don't know how much current the PCB can handle.  But it is safe to say that the MPG at 50 mA is no problem.  The 32 mA output limitation is for the output driver chips, and doesn't apply to the 5V output terminal.  If the power is being supplied by the USB, you might run into problems with using too much USB power.  The SS declares itself as a standard power device (100 mA).  I didn't want to comply with the requirements for a high-power device.  If it is high-power, it must first start as standard power, and then transition to high power (500 mA).  I didn't want to include the power management electronics.  But I don't think there is a problem if you use more than 100 mA.  If you do, and your computer doesn't like it, then you can use the external 5V input.  Then you can use a fair amount of current.  Easily an amp or more without a problem.

Hope this helps.


Re: SS MPG output current?
« Reply #3 on: July 11, 2008, 11:00:57 PM »
Hi Brett and Greg,

Thanks for that info.  I guess that a sourcing pin would not typically use to much current,  but if you had three pins using 30ma each,  then you would be pretty close to the 100ma standard USB limit.  I did get an error message from windows stating excess USB current with a Galil controller I was playing with about a year ago, so I guess there is some level of protection built in to the computer.  I will give the MPG a try and let you guys know what I see.  Thanks again,
Jim C.