BQ40Z60: When battery is close to full charge with adapter plugged in, device appears to cycle between charging and shutdown at 1-2 Hz rate

Aaron Needles

Part Number: BQ40Z60
Other Parts Discussed in Thread: BQ40Z50

We are having another troubling issue with the BQ40Z60 on our custom board. When the adapter is plugged in and the battery is charging, the following will occur when the battery is near a full charge.

Adapter volage is steady at around 18V. Most of the FET drives are ON as the device is cycled ON, but then turn off (except for CHG) when the device appears to shutdown for unknown reasons. This cycles repeatedly as you can see. REGN also cycles similar to what is shown.

I turned off all protections, and this did not change the behavior, so it doesn't seem to be due to a protection setup.

It does not matter if we are polling the device over SMB or not, we get the same behavior.

All is good when the battery is not fully charged. This only happens when our 4 cell LiPo is at around 16.4V and above.

Please let me know what might be happening here. This is another show stopper for us, and we have seen it on multiple boards.

Thanks,

Aaron

As shown top to bottom:

ACFET, Low Side FET, ACP, VSYS.

over 6 years ago

0 Aaron Needles over 6 years ago

Intellectual 615 points

5756.evmSettings700mAh - PROPOSED CHANGES 1 FOR v4.gg.zipThe parameter file being used

0 Batt over 6 years ago in reply to Aaron Needles

TI__Mastermind 42535 points

Are you seeing this on the evm or on your product?

0 Aaron Needles over 6 years ago in reply to Batt

Intellectual 615 points

On our custom board, and the same one that has had the issue titled: "BQ40Z60: ACP input held high after adapter is disconnected". I have not yet tried to replicate this on the EVM.

-Aaron

0 Batt over 6 years ago in reply to Aaron Needles

TI__Mastermind 42535 points

Can you please try it again on the evm? It may be related. You may also try it with rec temp charging voltage set to 4200mV. It may be related to chg termination.

0 Aaron Needles over 6 years ago in reply to Batt

Intellectual 615 points

I verified that the problem does not occur on the EVM, perhaps due to differences in loading or other subtleties. It occurs reliably on our PCBA.

On our PCBA, I tried the adjustment to Rec Temp Charging, but see no difference. The problem still occurs.

I had previously turned of all Protections A/B/C/D to see if any where causing this affect. The problem still occurs.

-Aaron

0 Batt over 6 years ago in reply to Aaron Needles

TI__Mastermind 42535 points

OK. That narrows it down. Are you using the same settings on both? If yes, it may be a layout or hardware issue. This is a difficult device to design in and we generally recommend the bq40z50 and a separate charger instead of this. But, I'll try to help you the best I can.

0 Aaron Needles over 6 years ago in reply to Batt

Intellectual 615 points

Yes, I was using the same settings in both cases and also the same 4S battery. The main difference would be the design, layout and the load that our custom board puts onto VSYS.

We greatly value feedback from your engineers on this issue. They may have seen this issue in other applications and so we sincerely hope you can get them to review this and to request more information if they need it. The design is working well in most operation scenarios, but we have this and the other serious issue that I posted in January.

Thanks,

Aaron