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Original question:

BQ25186EVM: BQ25186EVM

BQ25186EVM: BQ25186

Dante Fasano
Intellectual 300 points
Part Number: BQ25186EVM
Other Parts Discussed in Thread: BQ25186

Tool/software:

Hello Again,

I have one addtional question on the BQ25186 TSMR pin.

I am not using a thermistor for my application.

Is it sufficient to simply have a 100K pullup on the TSMR pin and a momentary switch to enter/exit SHIP mode?

Thanks in advance.

Dan Fasano

  • 0
    TI__Expert 8505 points

    Hi Dan,

    Thanks for reaching out.

    If a thermistor is not used on the TS/MR pin, connect a 10k resistor from TS/MR to GND. This ensures the pin remains in the valid TS voltage range for charging (TS Normal). A switch can also be connected to this pin for pushbutton functionality.

    Best regards,

    Alec

  • 0 in reply to Alec Lehman
    Intellectual 300 points

    Hi Alec,

    I tried just a pullup 100K on the EVM because the switch requires a pullup, that seems to work.

    Thoughts?

  • 0 in reply to Dante Fasano
    TI__Expert 8505 points

    Hi Dan,

    If the TS/MR pin is pulled up, the device will likely be in TS COLD, which suspends charging. However, if the TS_EN bit (REG0x7[6]) is set to 0 to disable the TS feature, then the pullup shouldn't cause any issues.

    Typically, a pushbutton on the TS/MR pin is used to pull the pin LOW when pressed. There is a 38uA current source on the TS/MR pin that is used for TS battery temperature monitoring and pushbutton press detection.

    Could you clarify the purpose of the pullup?

    Best regards,

    Alec

  • 0 in reply to Alec Lehman
    Intellectual 300 points

    Hi Alec,

    I didn't know there was a 38uA current source on the TSMR pin. So, with a 10K that only give 0.38V when the pin is not GND'd.

    I thought a pullup would be needed to allow the PB switch to be high when open and GND when pushed.

    Maybe this thinking is incorrect??

    I noticed on the EVM they have a 100K pullup and 100K pulldown, what is the purpose of that arrangement?

    I also wanted the switch on the TSMR pin to be read by a uP, so I needed a logic high and low.

    Dan

  • 0 in reply to Dante Fasano
    TI__Expert 8505 points

    Hi Dan,

    Yes, that's correct. A TS voltage of 0.38V is in the TS Normal region, which is between TS COOL (0.6700V typical, rising) and TS WARM (0.1850V typical, rising). When the pushbutton is pressed, the TS/MR pin is pulled to GND, causing the device to enter the TS HOT region which suspends charging. The TS threshold voltages can be found in the Electrical Characteristics table of the BQ25186 datasheet.

    On the EVM, resistors R3, R6, and R7 form a voltage divider that allows the TS feature to be evaluated by adjusting the potentiometer (R7).

    If the MCU needs to detect whether the pushbutton has been pressed, one option would be to do it using the INT pin and the WAKE1 and WAKE2 flags in REG0x1. When the pushbutton is pressed for a duration of tWAKE1, tWAKE2, or tLPRESS, an interrupt is generated on the INT pin.

    Best regards,

    Alec

  • 0 in reply to Alec Lehman
    Intellectual 300 points

    Thank again, Alec.

    So, to resolve this for my custom board that is not using a thermistor and the regs are set to disable the thermistor function.

    Should I simply incorporate what the EVM has, namely a 100K pullup/pulldown pair only?

    I am using the SHIP mode function and the WAKE functions by pressing the PB.

    It seems like I should disconnect the TSMR from my uP due to incompatible voltage levels?

    Dan

  • 0 in reply to Dante Fasano
    Intellectual 300 points

    Please respond ASAP since my custom board is going to fabrication tomorrow.

    Thanks,
    Dan

  • 0 in reply to Dante Fasano
    TI__Expert 8505 points

    Hi Dan,

    I'd recommend placing a pushbutton and a 10k resistor from the TS/MR pin to GND. And yes, with this configuration, disable the TS function via I2C.

    The TS/MR pin has an active 2.8V (typ) voltage clamp, so I don't recommend pulling this pin up. Ship mode can be entered either using the push button or via I2C, and the WAKE interrupts and flags can be used to detect button presses through software.

    Let me know if you have any other questions.

    Best regards,

    Alec