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BQ24616: Temperature Qualification

Kai Nomiyama
Expert 5545 points
Part Number: BQ24616
Other Parts Discussed in Thread: BQ24610

Hi Team,

 

I have a question about bq24616 Temperature Qualification.

 

Customer saw following problem and their TS network is here.

[TS network]

NTC thermistor=103JT

R9 = 2.2kΩ

R10 = 6.8kΩ

R16 = 100Ω (Change) → 1kΩ

C1 = 0.1uF (Change) → 0.01uF

 

[problem]

T1-T5 threshold is 0 to 60℃

 

Ta≒4℃

bq24616 repeats "suspend charge" and "start charge".

(suspend time=300ms/ charge time=400ms)

 

Ta≒5℃

bq24616 doesn’t go into "suspend charge".

 

When they change R16/100Ω to 1kΩ and C1/0.1uF to 0.01uF, there is no "suspend charge" at 4℃.

 

[Question]

  • The reason why T1 threshold is not 0℃ but 4℃?
  • How to fix this problem?
  • Whey they change R16/C1, they fix this problem. Do you know the reason of this and is it ok to use new R16/C1(1kΩ/0.01uF) value?

 

Please let me know if you have any questions.

 

Regards,

Kai

  • 0
    TI__Mastermind 24075 points

    Hi Kai,

    From your description, is TS fluctuating, causing TS to oscillate around the T1 threshold? Hysteresis is inbuilt so that minor TS oscillation doesnt cause the charger to flip between suspend and charge states. Can you take a scope capture of TS with original R16 and C1, and with changed R16/C1?

  • 0 in reply to Kedar Manishankar
    TI__Expert 5545 points

    Hi Kedar,

    Attachment shows TS and STAT1 capture.

    bq24616_TS.pdf

    Here is some comment for it.

    1) R16/C1=100Ω/0.1uF

    Adjust TS voltage by ext adj resistor to put bq24616 into 4℃ configuration.

    see charge and suspend.

    TS voltage is 2.35V - 20mV = 2.33V from capture

    2)R16/C1=1kΩ/0.01uF

    the same ext adj resistor with 1)

    see "NO" charge.

    TS voltage is 2.382V - 50mV = 2.332V from capture

    3) R16/C1=1kΩ/0.01uF with starting charge

    adjust ext adj resistor to start charging.

    See Suspend --> Charge

    TS voltage is 2.373V - 45mV = 2.328V from capture

    Vt1 is 3.3V*0.708=2.3364V typ so all of these TS voltage is close to Vt1.

    Regards,

    Kai

  • 0 in reply to Kai Nomiyama
    TI__Mastermind 24075 points

    Hi Kai,

       It looks like there is a voltage spike on TS i the first graph, which is causing the charger to think that IC is in T<0C. Can you capture TS spike along with falling edge of STAT. This should show us the value of TS voltage fluctuation as well as show the deglitch time for BQ24610 seeing the change. It looks like there is no issue when changing the value of R to 1k and C to 0.01uF. Most likely there is some higher frequency noise coupling on to TS which the higher value of R being more effective at attenuating this signal. There shouldn't be any issue with using their changed values.

  • 0 in reply to Kedar Manishankar
    TI__Expert 5545 points

    Hi Kedar,

     

    Here is STAT/TS capture.

     TS_STAT_capture.pdf

    VT1=70.2%_min/ 70.8%_typ/ 71.4%_max

    VREF=3.3V

    3.3V*0.702=2.3166V_min

    3.3V*0.708=2.3364V_typ

    3.3V*0.714=2.3562V_max

     

    From attached capture it looks deglitch time is 25ms.

    From the datasheet 25ms deglitch time is related with "deglitch time for temperature detection above/below T2/3/4 threshold.".

    However, customer saw charge/suspend so deglitch time for it should be 400ms(VTS>V1).

     

    Does it mean there is VTS>V1 event 400ms before we don’t see in capture?

    in addition, do you know the possible root cause of this voltage spike noise from your experience?

    I don't have EVM so I don't evaluate it but I think we don't see voltage spike on EVM so this voltage spike should be system level problem.

    if you have any advice to address it, please let me know.

    regards,

    kai

     

    Regards,

    Kai

  • 0 in reply to Kai Nomiyama
    TI__Mastermind 24075 points

    Hi Kai,

       I will verify tomorrow on EVM the deglitch time for out of range, You are right that datasheet specifies 400ms for out of range and that should be the deglitch time after the spike going high for charger to recognize TS fault. The spike does not happen on TS in the EVM. This is system level layout issue. Best solution is to change the RC value on TS as customer has validated that issue with TS spike does not occur on their board when they change R16, C1.(1kohm, 0.01uF)

  • 0 in reply to Kedar Manishankar
    TI__Expert 5545 points

    Hi Kendar,

    Here is 100ms/div capture in customer side while bq24616 is repeating suspend/ charging.
    It looks there is VTS>VT1 event as we can see in attachement and STAT pin is asseted by it after 432ms spike noise after 432ms.

    432ms_after_glitch.pdf

    they have already changed RC value and fixed this problem.

    Regards,
    Kai

  • 0 in reply to Kai Nomiyama
    TI__Mastermind 24075 points

    Hi Kai,

      Yes this is expected behavior regarding the TS deglitch time for out of range detection. Customer has resolved spike issue with new RC components.