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Original question:

BQ40Z50: bq40z50 / bq40z60 / bq40z80 - tapping PBI for enable pin function

BQ40Z50: bq40z50 / bq40z60 / bq40z80 - tapping PBI for enable pin function

Robert Andris
Intellectual 445 points
Part Number: BQ40Z50
Other Parts Discussed in Thread: BQ40Z80, , ,

Hi,

i also need an Indicator for the BQ in Shutdown or Enable in some way. I looked at the PBI Pin and did see that even though it does not reflect the Shutdown 100% it still drops down after some time. I dont want to supply any other circuit directly but instead just put a Gate from a FET on it (to only use this Pin as Signal and not as source) and would draw the equivalent of around a 2MOhms Resistor from that Pin. Would this be an approachable solution ?

I also thought about using the BTP_INT or  one of my unused Thermistorpins to get any other Signal that Indicates a shutdown BQ in wich the Timing is not critical as long as the signal toggles Off/On at all.

Do u have any Suggestions or Ideas ?  I was hoping that i can use the TS Pins as GPIO Pins like in the new bq40z80 to Map it accordingly but R2 does not support something like that.

Thanks in advance

Robert

  • 0
    TI__Expert 4645 points
    For the bq40z80, there is a GPIO mapping function that can be used to indicate many different states or flags, and can be combined with conditional logic to drive a GPIO as an interrupt. There is flexibility on the polarity of the signal, and three different types of GPIO depending on the logic levels or capabilities needed.
  • 0 in reply to Steve Schnier
    Intellectual 445 points

    Thanks for the Answer but i want to know if there is a similar function planned or allready available in a current or future firmwareupdate for the bq40z50. The Title only has the 40z60 and 40z80 because the original post i used the "additional" Question button had this Title and i could not change it. The used Chip is in Fact the bq40z50. I am at Layouting and really need an Answer fast because we need a Developmentsample for our customer. So the faster i can order the PCB the better. Right now i added a Resistordivider of about 2MegOhms to the PBI Pin to sense when the Voltage at PBI drops. Additionally i put in a path to TS1 and BTP_INT and made it so one of those 3 methods is selectable with unfitting and 0R Resistors in case there is a better Solution down the Road. 

    I cannot think of any reason why putting a 2MegOhm vs VSS to PBI for sensing might be a Problem but i really hope to get an Ok from TI for this exact Solution. To be clear, i dont want or need a Confirmation that under any circumstances this Pin reflects a corresponding State of the bq40z50, whatever i use the generated particular "Logic Signal" for is not critical nor can it lead to any unsafe Battery state. I "only" need the Confirmation that a 2MegOhm Resistordivider from PBI to VSS will not Interfere with the functions for this Chip except a rise in Supply Current that will be drawn.

    best regards

    Robert

  • 0 in reply to Robert Andris
    TI__Expert 4645 points
    We do have the bq40z50-R3 FlagMapSetUp feature that is similar to the bq40z80, however, it is limited to the three LED pins and DISP pin. If you aren't using the LED feature, this may be a solution for you. The bq40z50-R3 is a firmware release only, and can be flashed onto the bq40z50, bq40z50-R1, or bq40z50-R2 HW.
  • 0 in reply to Steve Schnier
    TI__Expert 4645 points
    Also, I have confirmed with design that a 2M Ohm resistor to GND on the PBI pin should not pose any issues.