• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 805 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ51050B: NTC design temperature adjustable?

Weinan Ji
Intellectual 265 points
Part Number: BQ51050B

Dear Support Team,

We are using this device as the wireless receiver in our project. The battery specifications for charging current is like this:

Cell surface temp.(Celsius)    Charge current

10 - 25                375mA max

26 - 45                750mA max

I wonder if we could set the temperature T1 = 10, and T2 = 25, and T3=T4=45 please?

If yes, how could we configure the NTC resistors then?

Thank you very much in advance!

Best regards
Weinan

  • 0
    TI__Guru* 75656 points
    It will be very difficult to adjust the NTC to meet the above requirements.
    Using an external circuit it MAY be possible, would control 45C point while NTC + BQ51050B controls the 10 to 25C points. BUT how to power the external circuit would be a problems.

    How large is the battery and what is charge current?
  • 0 in reply to Bill Johns
    Intellectual 265 points
    Hi Bill,

    Thank you for your quick reply.

    The battery capacity is 800mAh, and the charging current is as stated above. So when temperature is between 10-25, the battery is allowed to be charged with max. 375mA, and for temperature between 26-45, the max. charging current could be 750mA.

    I guess it is ok to define T1=10, and T4=45. However, T2 and T3 are predefined by some sort of percentage, right?

    As long as T2 will be higher than 25, the charging current will be limited to half of what it is defined, it will be safe to charge the battery when the temperature is between T1 and T2. Right?

    That was how I understood it from reading the datasheet. Please correct me if I am wrong.

    Thanks for your support :)


    Best regards
    Weinan
  • 0 in reply to Weinan Ji
    TI__Guru* 75656 points
    Hi Weinan
    Yes, the data sheet list the step points as % of V-TSB, 2.2V see below. What may be possible is to change the NTC and use an external resistor network to change T1 to 10C and T2 to 25C.
    But based on past work it will not be possible to adjust T4 to 45C. This would be an external circuit that monitor NTC and turn the device off at 45C.

    T1=0C, 58.7% of V-TSB, or 1.29V
    T2=10C, 47.8% of V-TSB, or 1.05V
    T3=45C, 19.6% of V-TSB, or 0.43V
    T4=60C, 13.1% of V-TSB, or 0.288V
  • 0 in reply to Bill Johns
    Intellectual 265 points

    Hi Bill,

    Thanks for your reply.

    Provided that we are open for any NTC and compensation resistor network. 

    If we would like to have T1=10, and T4=45, regardless of T2 and T3. Would you give you suggestion please?

    Thanks a lot :)

    BR

    Weinan

  • 0 in reply to Weinan Ji
    TI__Guru* 75656 points
    Hi Weinan
    I will contact you on this question.
    It does not look possible to do this with resistor network alone.
    Will require and external circuit to manage part of it.