I am planning to use the Arduino with a LiPo battery pack (with a dedicated USB charge and protect circuit) with a Buck-Boost converter with sets the LiPo's 4.2-2.9 V to a steady 3.3 V with a Texas Instruments TPS63001. Can I wire the regulated 3.3V to the 3v3 pin on the Arduino? Boosting up to 5V with an other Boost converter instead of the Buck-Boost converter mentioned above just to step down again by the arduino's MPM3610 using the Vin pin is a little inefficient I imagine
I tried both ways to power nano 33 ble and as you can imagine powering from Vin is less efficient than from 3.3v pin. To be more specific for a basic sketch where nano acts like a peripheral and sends gyro + accel values to a central device, powering from vin through a 5v booster the power consumption was ~18mAh. The same sketch consumes ~9.30mAh powering from 3.3v pin without any low power configuration. Just have in mind that in order to use direct the 3.3v pin you have to cut out the relative jumper on the bottom layer. Also, if you want to re flush nano board you have to connect the jumper again, otherwise usb connection does not work. I suppose for that you can do something with the Vusb jumper but i did not try it yet.
So as if i understand correctly I can wire 3.3V to the 3V3 pin under the condition:
Just have in mind that in order to use direct the 3.3v pin you have to cut out the relative jumper on the bottom layer.
Which means I have to break this connection marked with the blue square?
[EDIT: While doing more research on this I could not find any information on the SJ4 connection on the internet. The the only thing I was able to find and is mentioned everywhere is information about SJ1. Could you give me the source of the information about SJ4? What is the orientation of these pads? I am using the references from the official datasheet.]
But in order to send new code to the arduino I have to reconnect this jumper connection mentioned above. Did I understand you correctly?
If this is the case it bight be a good idea to add a NPN transistor that connects the pads when VUSB is present (picture below). I am still quite new to electronics so if someone could comment on if this is a good or bad idea I would be grateful