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Original question:

BQ25172: Using TS pin to control charging

BQ25172: TS pin as Enable/Disable

Shuhei Goto
Expert 5980 points

Part Number: BQ25172

Hi team,

I would like to use TS pin as to control charge enable/disable via MCU GPIO.

It seems that we should pull down to GND for charge disable.
On the other hand, what should do for charge enable? Floating is acceptable?

If you have the reffrene circuit for this usecase, it would be very helpfull.

Best reagards,
Goto

  • 0
    TI__Guru* 77356 points

    Hi Goto

    Shuhei Goto said:
    It seems that we should pull down to GND for charge disable.
    On the other hand, what should do for charge enable? Floating is acceptable?

    Yes, pull down to GND will disable charge, floating will enable charge.  BUT during floating the TS pin is monitoring NTC for temp and the current source is only 35uA.  The GPIO in floating condition needs to be high impedance for accurate temp monitoring.

  • 0 in reply to Bill Johns
    TI__Expert 5980 points

    Hi Bill,

    Thank you for comment.
    Let me add a bit more. In this case, we do not monitor the temperature.
    We would like to use TS as only Enable/Disable.
    Can we control charge Enable/Disable by switching the Hi-Z/Low output of the GPIO in the following configuration?

    Best regards,
    Goto

  • 0 in reply to Shuhei Goto
    TI__Guru** 106195 points

    Hello Goto,

    What is the value of Rpd? As Bill mentioned anything connected to the TS node needs to be high impedance otherwise it will impact the temperature measurement.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Guru* 77356 points

    Hi Goto

    Shuhei Goto said:
    We would like to use TS as only Enable/Disable.

    If NTC is not used then need a 10k pull down on (Rpd).  This will keep TS voltage at about 350mV - safe range is 188mv to 1.04V.  

    The GPIO needs to be low enough to keep unit in safe range.