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bq769x0 Shutdown and Wake Up

Jason Fuglestad
Intellectual 290 points
Other Parts Discussed in Thread: BQ76930, BQ77910A

Hello,

What pins are active in the bq769x0 during shutdown? Are the CAPx pins low to their respective references? I assume REGOUT would be off.

I'm going to use the bq76930, but I need a way to wake it up using a charge voltage instead of a switch. I was going to use one of the pins as a signal to disable my TS1 pull-up circuit if the AFE is already awake. Please let me know if you have a circuit that works.

Thanks in advance.

  • 0
    Guru 22270 points

    Hello Jason,

    The datasheets states that the VSTUP voltage is present along with the VBoot circuitry.  I am not familiar enough with the device to give you an exact answer.  If the LDO and REG where shut down and if your MCU relied on these then you would never be able to communicate with them.   An external reset would have to be used ((TS1).

    For a wake up on voltage level, you could implement a simple transistor 1-Shot circuit with the appropriate hold time for the TS1.  There are examples of this on the web.

    Thanks,

  • 0 in reply to Greenja
    TI__Guru 54715 points

    All output voltages are off when the bq769x0 is shutdown.  In your system you will have cell and battery voltages, or a charger voltage.  If you use a separate regulator for your micro you would have that voltage available. An appropriate switch or one shot as suggested should work.

  • 0 in reply to WM5295
    Intellectual 290 points

    Thanks for the response. I was able to design a circuit using a discrete solution that applies voltage to the TS1 pin only when the REGOUT is low and PACK- is low (when a charger is applied). The simulations prove promising.

  • 0 in reply to WM5295
    Prodigy 20 points

    Hi there WM5295, I have a similar issue, I am transitioning from the BQ77910A to the newer BQ76930. Since the first one got a note that it shouldn't be used for new designs.

    The issue I have is I was using the charger detect pin CHRGST to clear faults but the 76930 as far as I can see doesnt have a charger detect pin. Will bringing TS1 above 1000mV in the BQ76930 also clear faults? Or will it only wake it up, but leave both FETs open in case the fault caused them to be open?

    I am using an TMS320F280xxx, which I will be using for host controller to the BQ. But in the current architecture should both CHG and DSG fets open the TMS goes down, then how would I recover the system...

    Is there any application note discussing this kind of topic? Appreciate the support!

  • 0 in reply to Angel Cano 23
    TI__Guru 54715 points

    TS1 will only wake the device from ship, it will not clear faults.  Faults must be cleared by I2C access to the registers by a host (MCU).  The fault status must be cleared and the FETs must be set on by register writes.

    If using low side switching, a controller will be needed local to the battery, or an isolated communication path.  High side switching allows communication outside the pack.  If communication with the pack is needed when the controller is located with the AFE, the system still needs high side switching or some isolation method for the communication path.

  • 0 in reply to WM5295
    Prodigy 20 points

    Thanks for the answer WM5295, in my system the charger will provide power to the MCU directly tied to the BATT- and BATT+ terminals so in case of an error I could still (by plugging the charger) clear errors and re-engage FETs.

    In case of a battery replacement, then will provide a TS1 switch tied to one of the cells to wake the device up. It seems its all ready to go, thanks!