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BQ76942: TS2 Shutdown

Drey Platt
Prodigy 110 points
Part Number: BQ76942
Other Parts Discussed in Thread: BQSTUDIO,

Tool/software:

Hello,

I have my bq76942 connected to bqStudio and I am trying to get FET_EN to turn off when I pull ts2 low. I have tried multiple ways to configure TS2 Config however it still doesn't function. I have measured the voltage on the pin and never see a voltage higher than 2.3 volts and that is when the pin is set with the internal pull up resistor. What am I doing wrong?


Drey

  • 0
    Prodigy 110 points

    I have ts2 config set to 0x03 and it shows .3V on my multimeter. I don't feel this is high enough to trigger a falling edge for the shutdown command?

  • 0 in reply to Drey Platt
    TI__Expert 5705 points

    Hello Drey,

    Can you please share you schematic, .gg file, and clarify what you mean by trying to get FEN_EN to turn OFF when you pull TS2 low? I see you have the TS2 pin configured to an ADC input or Thermistor.

    FET_EN is also a bit the enables or disables FET Test mode in which these are typically controlled by the FET Test subcommands. This is shown in Table 13-34. Mfg Status Init Register Field Descriptions of the BQ76942 Technical Reference Manual.

    Are you just trying to turn off the FETs or leave Test mode?

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Prodigy 110 points

    Attached is the image of the schematic. I have ts2 on a switch that connects to a pull down resistor to gnd. I want to use TS2 to shutdown the BQ76942. Also attached is the gg file.

    6sBMS2.gg.csv

  • 0 in reply to Drey Platt
    TI__Expert 5705 points

    Hello Drey,

    I would recommend not using TS2 to try and shutdown the BQ76942. Typically, TS2 is used to wake up the device or is used as a thermistor/ADC input. For more information on SHUTDOWN mode, refer to this FAQ: BQ76952 Shutdown Mode FAQ.

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Prodigy 110 points

    Alexis,

    That is helpful thank you! So to clarify I should use a pull up on shut_down pin in order to put the battery in shutdown mode which will disable the discharge fets. but when I want to wake it back up I have to pull the ts2 pin to ground? I am looking for a simple way to shut off and turn on the battery discharge fets. I am basically trying to just use the bq76942 as a glorified switch.

  • +1 in reply to Drey Platt
    TI__Expert 5705 points

    Hello Drey,

    Correct, however, make sure the TS2 pin does not remain LOW when the SHUTDOWN sequence is initiated as the device will not enter SHUTDOWN and instead be stuck in SOFT SHUTDOWN mode.

    More information on FET control can be found in Section 5.2.3.2 FET Control of the BQ76952 Technical Reference Manual.

    Best Regards,
    Alexis