I find the following passage in the PF3000 Rev. 9 datasheet:
126.96.36.199 Coin cell battery backup
The LICELL pin provides for a connection of a coin cell backup battery or a “super” capacitor. If the voltage at VIN goes below the VIN threshold (VTL1), contact-bounced, or removed, the coin cell maintained logic is powered by the voltage applied to LICELL. The supply for internal logic and the VSNVS rail switches over to the LICELL pin when VIN goes below VTL1, even in the absence of a voltage at the LICELL pin, resulting in clearing of memory and turning off VSNVS. Applications concerned about this behavior can tie the LICELL pin to any system voltage between 1.8 V and 3.0 V. A 0.47 μF capacitor should be placed from LICELL to ground under all circumstances.
In the case where I don’t have a back-up battery connected to LICELL and I am concerned about the state of VSNVS when Vin < UVDET, what are my option?
- Can I apply 1.8V-3.0V generated by the PMIC to LICELL pin or the voltage source needs to be external?
- Do I need to disable the coin cell charger (Register COINCTL – ADDR 0x1A)?