Use 3VO as power input??

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cjames53
 
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Use 3VO as power input??

Post by cjames53 »

In a hurry on a new project, I misread the documentation initially and powered the Gemma-M0 with a 3.5V source soldered to the 3VO pin. It works great and I've had four of them running for months. However ... while reviewing the documentation recently, I realized my mistake.

My question is: will this work? I realize I'm supplying power to the output side of the voltage regulator. Will it be damaged? Will the Gemma-M0 work reliably by powering it with a well-regulated 3.5V signal to 3VO?

It would be very convenient if this works because, from what I can tell, the only other options are a USB or the JST connector, both of which are bulky and inconvenient for a device sewn into clothing. There is no other place to solder a power-supply wire.

Thanks!

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adafruit_support_bill
 
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Re: Use 3VO as power input??

Post by adafruit_support_bill »

A well regulated 3.5v source to the 3Vo pin will probably work fine - with a couple of cautions:
1) you should not connect it to USB when powered that way.
2) Analog readings will be affected - since your analog reference will be 3.5v instead of 3.3v.

A better way is to power via the VOUT pin. This is the same as powering via the JST connector. And it is diode protected so that you can safely connect via USB when powered that way.

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cjames53
 
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Re: Use 3VO as power input??

Post by cjames53 »

Thanks!

One clarification; I think your answer is clear but I want to be sure.

> A better way is to power via the VOUT pin. This is the same as powering via the JST connector.

If this is the same as using the JST connector, then I assume it needs a 4-6 volt input, not a 3.5 volt input, right?

Cheers,
Craig

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adafruit_support_bill
 
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Re: Use 3VO as power input??

Post by adafruit_support_bill »

What other circuitry do you have connected to 3Vo?

The voltage regulator is a "low dropout" type. It can reliably regulate power for the processor with a supply voltage as low as 3.4v.

However, if you have a lot of other circuitry pulling power from the regulator, it may need somewhat more than that.

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cjames53
 
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Re: Use 3VO as power input??

Post by cjames53 »

Got it, thanks again for your help.

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