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Original question:

BQ25125: Device waking up from ship mode even with short button press also.

BQ25125: Use of 100K NTC

Nicolas Tremblay1
Prodigy 20 points
Part Number: BQ25125
Other Parts Discussed in Thread: BQ25120A

Hello, is it possible to use a 100K ntc with this BQ25125?

Our battery have 100K NTC build in and I would like to know what kind of trick we can do to use this BQ25125 with a 100K NTC.

Thanks for your help!

Best regards,

  • 0
    TI__Genius 10545 points

    Hi,

    Unfortunately a 100K NTC is too far from the 10K specification which the BQ25125 is designed to meet. External resistors can help to compensate for certain NTCs but with a calibrated resistance of 100K, it is unfortunately too far to allow for external compensation.

    Just curious, why is there a preference for 100K NTC in your application? I'd like to know for future device development if a 100K NTC should be included as other possible standard NTCs.

    Best Regards. 

  • 0 in reply to Juan Ospina
    Prodigy 20 points

    Hello Juan, thank you very much for your answer.

    We have very low power consumption wireless medical device, so when we have made the request for custom battery (that has been certified for medical), we have chosen 100K NTC to ensure minimal consumption. 

    That's being said, we are developing a new product who will reuse same battery (since medical battery certification is really expensive).

    Any suggestion of device similar to BQ25125 who can fit a 100K NTC?

    Our NTC is 100K with a B=4250


    Best regards,

  • 0 in reply to Nicolas Tremblay1
    TI__Genius 10545 points

    Hi Nicolas,

    Unfortunately the devices of the BQ2512x family are all designed for a 10k NTC. The same is the case with the BQ2515x and BQ2518x families which are the next closest families of linear chargers I can think of.

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 20 points

    Hello Juan, Thank you so much for your time on this..

    I've used the TI tool (BQ25120A Setup Guide Tool.xlsm) and fitted the values of my NTC into the calculs and this look to work. Could you please help me to figure-out where is my error?

    My NTC: SDNT1608X104F4250FTF (100K with B=4250)

    From the Graph of my NTC, I've figure out that R(hot) is approximatively 22000 and R(Cold) is approximately 400000

    By fitting this into the TI tool, the tool return an RHi of 97.6K and and Rlo of 76.8K.

    So this tool looks to say it can work for BQ2512x parts... I'm little confuse now...

    Thanks Juan for your help!!

    Best

    Nicolas

    BQ25120A Setup Guide Tool.xlsm

  • +1 in reply to Nicolas Tremblay1
    TI__Genius 10545 points

    Hi Nicolas,

    My apologies! I had mistaken the TS feature of this family of devices for that of another group of devices I support which has current based TS sensing. Since this one is a voltage based TS then it should be able to handle higher resistance NTCs with the external resistors. Sorry for the confusion!

    The values that you shared for external compensation should work for a typical JEITA TS monitoring window.

    Best Regards.