Power Switching Solution for Battery + Wireless Charging Design

[aathil]

Hi everyone,
I’m working on a low-power BLE smart tag using nRF54L15 and nPM1300 PMIC. My requirement is:

When no charger is connected → the system should run from the 3.7 V Li-ion battery.

When wireless/wired charging is active (5 V to VBUS) → the system must remain OFF, and only the battery should charge.

Once charging is disconnected → the system should automatically power back on from the battery.

I’m currently exploring two options:
1️⃣ Using a load switch / ideal-diode controller to disconnect the 3.3 V rail during charging
2️⃣ Using a PMIC-driven control signal (e.g., VBUSOUT) to gate system power

Question:
 Are there any reliable, compact power-switching ICs you recommend for handling this “charge-only mode” automatically or can i achive this using NPM1300?

Any insights, recommended ICs, or reference designs are greatly appreciated! 

Thanks in advance!

[vasimv]

Not sure about nPM1300 but i've played with nPM1100 and found out the chip doesn't have undervoltage protection and will over-discharge battery to zero, so choose another IC or use battery with built-in over-discharge protection circuit.

Not sure why you would need to turn off power to MCU while charging, you may just check charging status in your firmware and do nothing if it is on a charger.

I've did similar project (BLE beacon with wireless charging) based on nRF52833, BQ51013B and BQ25121A as charging IC (it has battery undervoltage protection and quite useful 50nA shipping mode that could be used to shut down system completely when battery is low). https://github.com/vasimv/Everytag (Kicad project in the hardware folder).

[Priyanka]

Hi,

You could use the nPM1300 for this. When the VBUS is present, there will be a VBUSOUT. 

So one possibility is that, you could have a flag of VBUS presence on a GPIO, then loop it to another GPIO that would enable/disable the BUCK. 

Hence, when there is VBUS present, the GPIO causes BUCKs to be disabled, and viceversa when the VBUS is removed.

You could do this, but controlling one of the internal load switches with a GPIO and keeping the DCDC ON.

-Priyanka