nPM1300 operation

[Dave M]

We're using the nPM1300 in our designs and we noticed that the charge portion does not appear to keep a battery charged when USB is connected for extended periods.

Our arrangement is that we have a feed from the battery going to a circuit which gets pulsed on and off.

If USB is connected for extended periods the PMIC will charge the battery once and stop.

If the battery voltage drops below ~3.0 volts, the PMIC does not automatically trigger a recharge.

Some OTS chargers exhibit the same characteristics.

We can get around this by drawing from VSYS rather than directly from the battery.

I wanted to avoid the high current spikes going through the PMIC.

[helsing]

Hi Dave, 

Just letting you know we have started looking into this. Would you be able to share some more details regarding your setup, like schematics and configurations? You may make the ticket private in case you do not want to share the schematic openly,

[Tharaka]

Hi

This is essentially a different use case than what the recharge logic was designed for (i.e., slow battery discharge), especially when the load is connected directly to VBAT instead of VSYS. In such cases, the charger state machine may not behave as expected and may stop initiating recharge.

Even if charging starts, a sudden drop on VBAT caused by the load pulse could interrupt the charging process. Worth checking the Charge error and Latched error reasons registers (BCHGCHARGESTATUS, BCHGERRSENSOR and BCHGERRREASON)  to see if any charging error has been triggered in this condition. Would it be possible to design the system such that the pulsed load on VBAT is not present while charging is in progress?

We need more detail on the pulsed load connected to VBAT, specifically the peak current, pulse duration, repetition rate?
Can we get a scope trace to see the battery voltage waveform during these pulses?
Also does the battery include a PCM/protection circuit and what is the battery capacity?

Also check, Enable charging at low battery voltage  option, if the PCM or low battery voltage stops battery being charged.

Note that the host can force a recharge by toggling the charger enable periodically, even if automatic recharge was not triggered.You need to handle this in SW.

Regards

Tharaka