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BQ24040: NTC recommendation

Amelie Zheng
Genius 10865 points
Part Number: BQ24040

Hi Team,

he TS pin of BQ24040 uses NTC, and the NTC PAD is laid out on the PCB. The current NTC selection is "NCP15XH103F03RC", and a specification sheet is attached.

NCP Series DATASHEET.pdf

1. The current test found that when the temperature is between 40 degrees and 45 degrees, it is thermally protected and cannot be charged, and the battery is not overheated at this time. (NTC mainly detects the temperature of the shell space)
2. Under the condition that the low temperature conditions of BQ24040 remain unchanged, can you recommend a NTC thermal protection temperature higher, such as 60 degrees-65 degrees.
3. The PCB layout and SCH are as follows:

  • 0
    TI__Mastermind 31810 points

    Hi Amelie, 

    The BQ24040 follows the JEITA profile for battery temperature monitoring. The device is configured to disable charge when the battery temperature reaches approximately 60C, and reduces the regulation voltage to 4.06V when the temperature is between approximately 45C and 60C. These temperature estimations are using a TI recommended thermistor for the device (SEMITEC 103AT-2 or Mitsubishi TH05-3H103F).

    Using the spec sheet you provided I calculated the expected operational range using the customers NTC. I calculated the voltage on the TS pin should be 290 mV at 40C and 245 mV at 45C. These voltages are both well above the voltage falling threshold for high temperature protection (178 mV). Based off my calculations with the customers current NTC they should not see the disabling of charge due to high battery temperature until approximately 55C.  

    Can you please have the customer provide more details on the testing they did. Particularly the voltage on the TS pin and resistance of the thermistor when they are unable to charge due to high battery temperature. Via calculations the NCP15XH103F03RC should allow operation to a higher temperature than 40-45C.

    Best Regards,

    Garrett