Connecting PowerBoost 1000C to Arduino Pro Mini 3.3V

The title almost says it all. I am trying to understand how to connect the PowerBoost 1000C to a Arduino Pro Mini 3.3V and a single 5V powered open collector output sensor.

My initial thought is: Vs - Arduino Raw In (as it can handle 3.3-12V) GND - Arduino GND

5V - Sensor Power GND - Sensor Ground

For completeness (though slightly irrelevant, sensor output to Arduino Pro Mini input using internal pullup.

The question comes on the EN and LBO pins. The schematic shows both connected to Vbat. Vbat should range from 3.0/3.2V to 4.2V or so. But the Atmel 328P chips can only handle Vcc+0.5V on the input pins, or 3.3+0.5=3.8V. So the EN and LBO pins will be 0.4V higher than the micros absolute maximum rating. Do I have this correct? How do I connect the LBO and EN pins to a 3.3V chip?

P.S. I'm not sure whom to better answer this, the folks at the Adafruit site or here, so I did post in both places. Forgive me.


I have read it, printed it, made notes on it and read it again.

So based on the original plan you do not think it is possible to connect the LBO and EN pins from the PowerBoost directly to the 3.3V Pro Mini?


If I am reading the datasheet correctly, the absolute max Vcc is 6.0V. I don't see a separation between the 3.3V or the 5V versions.

I'll be conservative and say the absolute max is designation + 1.0V which makes the 3.3V an abs max of 4.3V Vcc. That would make the max input 4.8V. That works to be compatible EN and LBO voltages.

Some questions:

Is the absolute max Vcc of the 3.3V 328P actually 6.0V (datasheet page 299)?

According to the schematic for the Pro Mini, SJ1 (jumper? solder jumper?) connects/separates the onboard voltage regulator (RAW in) from Vcc. What if I remove the jumper and connect the Pro Mini Vcc directly to the PowerBoost load share Vs pin?

What are the ramifications of running the 3.3V Atmel 328P at a higher voltage than specified? What changes should I expect to see? Clocks run faster, slower? ADC issues? Etc.

Rather than start a new thread, I thought I would amend this one. I have the PowerBoost 1000C connected to the Pro Mini with the Vsh out connected to Pro Mini Vcc (and the solder jumper removed). Everything appears to be within specs. So far so good. I tried to connect the PowerBoost LBO pin to an input of the Pro Mini (also tried an UNO). When I do, the LBO red LED on the PowerBoost lights. I have not been able to figure out why. Any one have any ideas? Is it an issue with the PowerBoost, bad Arduino software configuration, bad board? Thoughts, questions.