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Original question:

BQ2980: How to use an external PTC for undertemperature and overtemperature detection

BQ2980: How to use an external PTC for undertemperature and overtemperature detection

Jeff Lam55
Intellectual 420 points
Part Number: BQ2980

Hi, I am planning to use BQ298015 for battery protection in my product: I have some questions regarding over-temperature and under-temperature protection.

 

1. Based on the datasheet, seem like the overtempature protection is fixed at 85C for this part. Is this true or we can adjust the temperature level by adjusting the PTC value?

2. Can you recommend a PTC part number to turn off the CHG and DSG outputs when temperature is over 85C? 

3. How do I know what is the value of the internal pull-up for the part that I am choosing?

4. Looks like Rpull_up is pulled up to VDD. Is VDD regulated? What is the accuracy of the temperature sensing?

5. Can you explain how does the undertemperature work? Can you have OT and UT protection or it is just one or the other (since there is only one CTR input)?

Thanks,

Jeff   

  • 0
    TI__Guru* 76230 points
    Hi Jeff
    We will get back to you shortly by midweek
    thanks
    Onyx
  • 0
    TI__Genius 10370 points

    Jeff,

    Here are the answers to your questions

    1)  The 85C is an internal temperature setting which will trip at 85C, +/-10C. There is additionally an external Method via the CTR pin where you would use a PTC to create a voltage divider to trigger the CTR pin. 

    2) We do not have a recommended part number. Figure 5 in section 7.6 of the datasheet will show a plot of the pull-up resistance over a sweep of VDD points. for the different pull-up options, but see #3 about the current order able parts.

    3) Currently on on the order-able parts there is no pull-up. We do have the other options, but that would require a custom spin which i will need to bring in the business team to discuss with you on the options.  

    4) It is essentially pulled up to Vbat minus an unregulated diode. 

    5) Under temperature will work the same way of the over temperature, but instead use an NTC instead of a PTC. You are still creating the voltage divider to toggle between the trip threshold of the CTR pin. To trigger on both OT and UT. You could order the part with the internal OT protection and use the CTR pin for the UT protection. 

    let me know any further questions.

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Intellectual 420 points
    Thank you for your reply! I think you clear up most of my questions.

    Some follow up questions:
    3) Currently on on the order-able parts there is no pull-up. We do have the other options, but that would require a custom spin which i will need to bring in the business team to discuss with you on the options.

    Does this mean we need to request for a custom spin in order for this part to support overtemperature protection feature? If I understand correctly, an internal CTR pull up resistor is required for the CTR pin to work.

    For VSCD, OCC and OCD and all the other factory configurable settings, do I need to provide my system spec to your team for custom spin as well?
  • 0 in reply to Jeff Lam55
    TI__Genius 10370 points
    Jeff,

    1) If you would like to modify the settings for SCD/OCC/OCD yes we would need to create a custom spin.

    2) The internal over temperature feature will still work if you order the part with that option. Aside from that you could always attached an external pull-up / voltage divider circuit to create the same effect.

    Hopefully this answers you question.

    Thanks,
    Eric Vos
  • 0 in reply to Vos
    Intellectual 420 points
    Thank you for the clarification.

    One last question, I noticed under "Device Configuration Options", those parts already have specifications for OCC, OCD and SCD in (mV). Do they correspond to amp if I use 1-mOhm resistor?
  • 0 in reply to Onyx Ahiakwo
    Intellectual 420 points
    Thanks! That's all the questions I have.