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BQ769142: Disabling PCHG on the fly, Enter manual mode in the fly

Olivier Nguyen
Prodigy 60 points
Part Number: BQ769142
Other Parts Discussed in Thread: BQ76952

Hi TI forum,

We have successfully integrated your BQ769142 in our design and are very pleased with it. The protection, cell balancing and monitoring work like a charm.

We are now willing to add higher level functions, and I couldn't achieve what we wanted to do yet. Maybe you could help?

Question 1) Is it possible/Is there a command that I can send to disable PCHG Fet while it's active? I know that PCHG FET has a STOP voltage as well as a Timeout, but is it possible to disable it "manually" by sending a command while it's charging?

Question 2) I didn't really understand how to enter full manual mode? In some scenario we need don't want the FET to turn off even if there's a fault. What we were thinking was to have a "manual" mode where the BQ76 sends to the host controller that there is a fault, but the host doesn't deactivate the FET.

At the moment the BQ76 is in full autonomous mode, and thus deactivate the FET as soon as there is a fault.

How can we enter full manual mode (the BQ76 only indicate there is a fault without deactivating the FET) and how to enter this mode on the fly (imagine we have a device that can move around, and we don't want that device to have a fault and stop in certain rooms because of safety. It would be nice to be in room A in full autonmous mode, and before entering room B switch to full manual mode. Is this possible?)

Regards,

O.

  • 0
    TI__Guru* 81034 points

    Hi Olivier,

    I do not think there is really any way to control the PCHG FET manually from the host. The PCHG and PDSG features are enabled based on the configuration settings, so the stop voltage and timeout are really the only ways to transition from PCHG to CHG. Changing configuration settings during operation requires entering CFG_UPDATE mode which disables the FETs. You can always use the CHG_PCHG_OFF() command (or the CFETOFF pin) to disable the PCHG FET, but this will also prevent the CHG FET from being enabled.

    Full manual control requires changing the configuration registers. You can clear the bits in the registers below to prevent the BQ76952 from disabling the FETs based on the protections. However, there is no easy way to change these settings on the fly.

    Maybe you could consider each of the protections to associate with the CHG FET and DSG FET and use a partially autonomous approach. So when you are in room B, there would still be some protection conditions that would disable FETs, but for other conditions the decision will be up to the host contoller?

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 60 points

    Hi Matt,

    Thanks for your reply.

    Too bad that Alarm Register Enable 0x66 only acts on the the alarm status / ALERT pin but doesn't act directly on the FET. It would have been the best solution as 0x66 can be modified on the fly.

    I'll figure out a new strategy then.

    Thanks for your help.