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BQ51013B: Temperature control (pin TS/CTRL)

user4498844
Prodigy 165 points
Part Number: BQ51013B

Hey,

I have a problem with the temperature of the metal housing around the receiver coil.  Just the temperature is too high!
I want to use the NTC temperature sensor to solve this problem.

For example in datasheet, there are resistors R1 (4.23k) and R3 (66.8k) connected to the TS input for temperature control from -10 to 100C. I hope that I understood the scheme and graph.

I want the housing temperature to be lower than 40C, I use the NTC 10k thermistor and R1 = 12k and R3 = 66.8k. For these values, I calculated that% HOT = 33% and% COLD = 63%.

The effect - does not work. Even when I changed the thermistor to a 10k potentiometer, the device totally ignored the signal from the potentiometer.

Where did I make a mistake?

In addition, I have a question, what is hepend when the temperature is too hot? BQ stops charging or limits output power?

And one more question, the voltage Vtsb and resistor R2=20k... I understand that these are elements are inside the BQ?

  • 0
    TI__Guru* 75996 points
    V-TS (HOT) -- 0.431V (19.6% of VTSB)
    V-TS(COLD) -- 1.291V (58.8% of VTSB)

    For a -10C to 40C range the NTC beta will need to be higher, one possible solution:
    NTC Beta -- 4500
    NTC Ro -- 10k
    R1 -- 608
    R3 -- 45.7k

    Yes, the VTSB voltage and resistor R2 are internal to the device.

    When the voltage at TS pin is outside the above range (below 0.43V or above 1.29V), the RX will send a command to the TX to turn off and TX will show a thermal fault.
  • 0 in reply to Bill Johns
    TI__Guru* 75996 points
    The thermal rise is due to metal heating in an AC field, a couple other options:
    1.) Reduce the AC field size by reducing output power from the bq51013B, change ILIM setting.
    2.) Thin magnetic shielding material is available. It could be placed between the coil and metal of the case.