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BQ25101: /CHG keeps low when there is no current

Hao Wang14
Expert 4415 points
Part Number: BQ25101
Other Parts Discussed in Thread: BQ24090, BQ24090EVM

Hi Team,

The pin description of /CHG tells it goes low (FET on) when charging and open drain (FET off) when no charging, some tests don't match the description:

The NTC is connected on TS pin, and /CHG pins is pulled up to 5V.

1. When BQ25101 is put into the ambient under 0℃ or over 60℃ for more than 30 minutes,  then plug the power adapter, /CHG pin goes high whether the load is 3.6V electronical load or battery, and the current from power adapter is almost zero.

2. When BQ25101 is put into the ambient and plug the power adaptor, BQ25101 starts charging, then raise the temperature over 60℃ or lower the temperature below 0℃, /CHG pin keeps low with 3.6V load, but the current from power adapter is zero.

Could you please help confirm why sometimes /CHG keeps low when there is no current?

Thanks and Best Regards!

Hao

  • 0
    TI__Mastermind 19195 points

    Hi Hao,

    Can you attach the schematic for review.

    Thanks

    Nick

  • 0 in reply to Nick Brylski
    TI__Expert 4415 points

    Hi Nick,

    Here is the schematic, R5 is the NTC, the part number is NTCG063JF103FTB.

    Best Regards!

    Hao

  • 0 in reply to Hao Wang14
    TI__Mastermind 19195 points

    Hello Hao,

    When you remove the 20k pulldown on /CHG do you see the same behavior? The pulldown is not needed here.

    Best regards,

    Nick

  • 0 in reply to Nick Brylski
    TI__Expert 4415 points

    Hi Nick,

    While checking the pull down resistor, could you please tell the conditions when /CHG turns high? Thanks!

    Best Regards!

    Hao

  • 0 in reply to Hao Wang14
    TI__Mastermind 19195 points

    /CHG would be high when not charging and when charging reaches termination.

  • 0 in reply to Nick Brylski
    TI__Expert 4415 points

    Hi Nick,

    The test on BQ25101 and BQ24090 are the same where /CHG doesn't turned high when there is no charging current.

    We also tested on BQ24090EVM, the power supply is 5V and the battery(3.3V~4V) is connected, here is the test steps and /CHG status by changing the resistance of potentiometer R11:

    1. When TS voltage is between VTS-60°C and VTS-0°C, /CHG is low as the LED D2 is on.

    2. When TS voltage is higher than VTS-0°C to simulate the cold environment, there is no charging current, however /CHG is low as the D2 is always on rather than off.

    3.  When TS voltage(such as 0.17V) is a little below VTS-60°C to simulate the hot environment, there is no charging current, however /CHG is low as the D2 is still on. /CHG turns high as The D2 is off until the TS voltage reaches 0.04V or lower.

    The test clearly shows that /CHG pin doesn't turned high when there is no charging current, could you please help confirm why /CHG isn't turned high when there is no charging current at 60°C and 0°C?

    Thanks and Best Regards!

    Hao

  • 0 in reply to Hao Wang14
    TI__Mastermind 19195 points

    Hello Hao,

    For this test is the pulldown still present?

    Thanks,

    Nick

  • 0 in reply to Nick Brylski
    TI__Expert 4415 points

    Hi Nick,

    We ordered a BQ24090EVM, so the test is done on BQ24090EVM(BQ24090EVM Evaluation board | TI.com), BQ25101 has the same problem. I think you can also replicate this problem, could you please help confirm the conditions when /CHG turned high?

    Thanks and Best Regards!

    Hao

  • 0 in reply to Hao Wang14
    TI__Mastermind 19195 points

    Hello Hao,

    I will take a look at this next week you can expect to hear back then.

    Thanks,

    Nick

  • 0 in reply to Nick Brylski
    TI__Mastermind 19195 points

    Hi Hao,

    Hao Wang14 said:

    2. When TS voltage is higher than VTS-0°C to simulate the cold environment, there is no charging current, however /CHG is low as the D2 is always on rather than off.

    In my testing on the bq24090EVM I was not able to replicate this. What was the value of the TS in this case?

    Hao Wang14 said:
    3.  When TS voltage(such as 0.17V) is a little below VTS-60°C to simulate the hot environment, there is no charging current, however /CHG is low as the D2 is still on. /CHG turns high as The D2 is off until the TS voltage reaches 0.04V or lower.

    It is possible in this case that the threshold was not reached. The minimum is 0.170V, is the LED still on when it is under this voltage?

    Thanks,

    Nick

  • 0 in reply to Nick Brylski
    TI__Expert 4415 points

    Hi Nick,

    May I know your test conditions for the second question? Because our test shows that BQ24090EVM may work well with electronical load, but it cannot work well if the battery is connected.

    For the third question, we monitored the voltage on TS pin, even the voltage is slightly lower than 0.17V, /CHG is still low, /CHG turns high when the TS pin voltage around 0.04V which is far less than 0.17V.

    Could you please double confirm with the battery as the load with the voltage within 3.6V~4V?

    Thanks and Best Regards!

    Hao

  • 0 in reply to Hao Wang14
    TI__Mastermind 19195 points

    Hello Hao,

    Sorry for the delayed response.

    I was able to see identical behavior in case 2 & 3 with bq25101, using 5V supply on IN and battery simulator at 3.6V on OUT. I altered the TS voltage with potentiometer. 

    Hao Wang14 said:

    2. When TS voltage is higher than VTS-0°C to simulate the cold environment, there is no charging current, however /CHG is low as the D2 is always on rather than off.

    3.  When TS voltage(such as 0.17V) is a little below VTS-60°C to simulate the hot environment, there is no charging current, however /CHG is low as the D2 is still on. /CHG turns high as The D2 is off until the TS voltage reaches 0.04V or lower.

    As stated in the d/s 8.3.2, the /CHG pin is low during the first charge. If the NTC resistance is out of range before adapter is connected charge never begins and so /CHG does not go low. Pulling the TS pin low causes /CHG to reset. In your case 2 & 3, it is possible to turn off the LED also by cycling input power. 

    Best regards,

    Nick