Battery power supplu to CUI32

[roland]

Dear all,

I would like to provide external battery power to the CUI32.

My PCB underside says "3.5-10V" at the battery connector (by the way, on the PCB photo on sparkfun it seems the PCB says "3.5 to 5.5V !??) but from the schematic it is not clear to me if I can directly connect a 9V battery (for example). To me it looks like this would put 9V on the 3.3V DC/DC input (which would be OK) but as this is normally 5V (when USB powered) it seems I would get 9V on the USB pins and also on pin34 of the PIC (which is conncted to the 5V). Having the 9V on the PIC looks very unhealthy to me.

To cut it all short: Can I directly connect a 9V battery (and if, why) or do I need a 5V regulator (or similar) ?

Many thanks !

Roland

 

 

[Markus Gritsch]

IMO it is not safe to connect 9V to the SparkFun boards.  We discussed this in the forum a few month ago

http://overtone-labs.ning.com/forum/topics/zigflea-for-cui32?commentId=3789944%3AComment%3A1764

 

and the latest PCB version in SVN has this fixed.  I brought this issue to SparkFuns notice, but they will sell the old boards until they have used all their already manufactured PCBs and MCUs.

[Dan Overholt]

True, what Markus mentions ... but it any case, the small surface-mount regulator (Micrel MIC5216) used on the CUI32 would be challenged to output very much current when used with larger input voltages, without overheating. It can handle a pretty good load (500mA) when dropping 5v down to 3.3v, as is normally the case - but 9v down to 3.3v is a much bigger task.

 

You can check the datasheet for specifics:  http://www.micrel.com/_PDF/mic5216.pdf