Dual 3.3/5V supplies from single cell lipo

Other Hardware General Electronics
1

Hi all, I am a hobbyist whose skill level is butting against project requirements - any help is appreciated:

My goal is to power two components in my project with a single cell lipo:
mcu: ATSAMD21G18 (3.3V/100mA)
radio: E32-915T30S (5V/680mA)

Right now, my understanding is that I will need to do this using three separate circuits:

  1. Lipo charging circuit using DC/USB/Solar Vin
  2. LDO regulator for 3.3V
  3. Boost converter for 5V

This project will spend most of its time in sleep - so I am setting myself a design goal of ~50uA sleep current to give 1yr on a 500mAh lipo.

Yes I can probably do this with parametric searches on component sites but given that almost all are smd components and I have little design experience, I have no idea how to prototype this without 10 bad pcbs and false starts.

Has anyone dealt with similar requirements before and can you share your solution ? Just to clarify, I can solder SMD components so that's not a blocker.

2

What is the allowable voltage range on the microcontroller? Often they are wide enough to accept a lithium battery directly. The AVR processors common to Arduinos will run just fine direct to the battery so long as the clock speed is set to 8MHz.

Then there are no losses associated with powering the microcontroller. It can sleep as required and you don't have any parasites sucking energy during sleep.

Choose a boost supply that is controllable. Many of the Pololu ones are. So the microcontroller can turn it on only when necessary.

3

Hi, Thanks for the suggestion MorganS.

Unfortunately, the SAMD21 (also used in Arduino Zero) has a Vmax of 3.63V (ATSAMD21G18)
So, I probably should not hook it to unregulated lipo.

I could fall back to using an atmega328p but then I won't be able to use this nice low power display (Adafruit SHARP Memory Display Breakout - 1.3 168x144 Monochrome : ID 3502 : $24.95 : Adafruit Industries, Unique & fun DIY electronics and kits)

4

Hi,
I think you may be looking for this;

https://www.aliexpress.com/item/ESP32-ESP32S-For-Wemos-For-Raspberry-Pi-18650-Battery-Charge-Shield-Board-V3-Micro-USB-Port/32870411748.html?aff_platform=link-c-tool&cpt=1547641289273&sk=ccgnehR2&aff_trace_key=0d8387ef1c034523bc727a026aed2197-1547641289273-02964-ccgnehR2&terminal_id=30b967f90dbd4e559b5eb5655c234f1a

Andreas has a YouTube video on it;

I have a couple on order, they haeven't arrived yet.

Tom... :slight_smile:

5

Thanks Tom! This is exactly the kind of thing I am looking for.
And its much cheaper than this item I found on tindie.com yesterday:
https://www.tindie.com/products/ceech/lipo-charger-boost-converter-5v-33v-outputs/