Bytter

Power Papilio Pro from a 3v3 source

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I'm wondering if it is possible to power the Papilio Pro directly using a 3v3 source (in my case, I want to use a 3.7v LiPol battery + linear regulator), instead of the usual 5V.

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Since the oscillator, flash and memory are all working through 3v3 (if I'm not missing something in the diagrams), wouldn't a direct power injection on one of the 3v3 wing pins do the trick?

 

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Ok, VCCINT requires 1.2v :-\

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Hello Bytter,

 

We need to look at the datasheet for the switching voltage regulator to answer this question. The datasheet says: "Low dropout operation: 100% duty cycle" this sounds good for your application. The dropout is how much higher the input voltage has to be then the output voltage for stable operation. I'm taking what the datasheet says, "100% duty cycle provides low dropout operation, extending battery life in portable systems." to mean that it can operate at 100% duty cycle which means that it can take a 3.3V input and pass it through as a 3.3V output. So it should be able to handle a 3.7V input with no problem, just be sure to connect the battery to the VIN rail, not the 3.3V rail. You want the voltage regulator to generate the 1.2V VCCINT power also. The only downside is that 3.7V will be presented on the 5V wing power pins so just be aware of that. You probably don't have any wings that need 5V anyway so it should be good. 

 

Jack.

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