Li ion cell charging and protection circuit for powering STM32WLE5JC

[David_]

Appreciate pointer to information.  New to these.  To power the STM32WL5EJC, we need to make a custom board incorporating the charging and protection circuit since 30mAh Li ion cell does not have build-in protection board.

Appreciate circuit diagram, for or similar to, the popular Li ion cell charging board using TP4056 and protection chip DW01A.  Presumably, circuit need to auto switch cell in and out of circuit so the charger chip will end charging at 10% of current (3mA for 30mAh cell) going into the cell and not counting current feeding the STM32WLE5JC (6mA radio receive, 30mA radio transmit).

We plan to use MCP1700, Linear LDO, to take Li ion cell 4.2V to 3.0V for STM32WLE5JC.   Many thanks

[Peter BENSCH]

You should describe the requirements and environmental conditions of your application a little better so that this can be taken into account. You may have asked about battery types in another thread, but it's still not completely clear, at least to me.

• Where does your charging voltage come from?
• In what voltage range do you want to charge?
• Should your system continue to work during charging or switch off during charging?

Regards
/Peter

[David_]

Many thanks.

I got the circuit from web reply.  Use TP4056 as charger chip and DW01A as cell protector chip.

https://support.envistiamall.com/kb/tp4056-dw01a-microusb-5v-1a-18650-lithium-battery-dual-function-charger-board-with-protection-module/

I believe the charger chip use constant current mode (15mA at 0.5C rate for 30mAh cell) for bulk of the charging time.  Then switch to constant voltage mode and charge current drop to 10% of 15mA euqal 1.5mA, then, charging completed.

1.  Power supply is (micro USB or type C) USB 5V or traditional wall adaptor (with round connector dated four decades old style)

2.   cell is Li ion, 3.7V rated, 3V fully discharged, 4.2V fully charged, cell capacity 30mAh to 70mAh

3. If STM32WLE5JC is operational while battery is charging, the radio takes 7mA in receive and 26mA on transmit and 1 micro amp at STOP2.  This will confuse the charger chip for end of charging detection (below 1.5mA, 10% of constant charging current)

I read that some design will disconnect cell from load and ONLY connect cell to charger chip.  The external power supply will feed the load (STM32WLE5JC) and the charger.  This is same as cell phone.  User can use phone while connect to USB for charging.

I wonder if below circuit do this.  I perfer STM32WLE5JC runs all time.  If not, I can switch off STM32WLE5JC while cell is connected to charging power supply.

Many thanks

[Peter BENSCH · Accepted solution]

In principle, you can use this board with two devices to charge your battery - however, you also need MOSFETs and  some additional electronics to control to switch the radio system including its regulator from the battery to the input voltage. All in all, a complex variant, don't you think?

Why don't you take a look at the STBC02, which already has everything integrated?

Regards
/Peter

[David_]

Many thanks for excellent advises.

How about STNS01 which is easier on PCB without BGA? 

Does it also draw very small current from cell when USB wall charger unplugged?

[Peter BENSCH]

Yes, STNS01 would also be an option, but with slightly more current from the battery when the charger is not connected, which is why I didn't mention it originally. You will find the values while searching for BAT pin supply current > Battery-powered mode.

Good luck!
/Peter

[David_]

STNS02 is nice. 

Will STNS02 work with Li ion cells that come with protection chips (yellow tape in photo)