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BQ25185: SYS does not detected when the battery is connected.

Chase Jeong
Mastermind 6140 points
Part Number: BQ25185

Tool/software:

Dear TI experts,

My customer now tests BQ25185 in their own PCB.

And sometimes they find the symtom that SYS does not detected when the battery is connected.

1. While production, they connect the battery to the PCB after every parts are assembled.

2. And sometimes, SYS does not detected after they connect PCB.

3. The voltage is over 4V when they tested.

4. Once they find this symtom, they apply 5V to VBUS, finally they can see the SYS voltage.

5. In other way, they disconnect the battery and connect again, they can see the SYS voltage. (and if they cannot see SYS voltage, they disconnect and connect again. max 4 tries) 

6. They tested 50 PCBs with 1 same battery(this battery is over 4V), they found 3 PCBs which SYS does not detected.

I saw about the Factory Mode in the datasheet. And it looks like enter factory mode sometimes when the battery is connected.

But datasheet says thet the user can activate factory mode by push button through TS/MR pin. and there is no other way.

(My customer uses this pin for TS, not MR)

Could you help me to solve this problem? Finally my customer want to do function test without applying VIN while production.

I attach the schematic for your convenience.

Please let me know if you ieed more information. Thanks.

Best regards,

Chase

  • +1
    TI__Expert 3525 points

    Hello Chase,

    Thank you for providing the schematic.

    Chase Jeong said:
    I saw about the Factory Mode in the datasheet. And it looks like enter factory mode sometimes when the battery is connected.

    It is possible that the device is entering factory mode when the battery is being connected. I see that there is no push button on the TS/MR pin; however, please verify that nothing is pulling the TS/MR pin low during assembly, which could cause an unintended ship mode entry.

    I see that there are 2x 47uF caps on the SYS pin. This is very close to the maximum 100uF capacitance that we recommend on this pin. Please refer to section 9.2.2.3 of the BQ25185 datasheet. It's possible that inrush current from the battery to these SYS caps is triggering BATOCP, which would disconnect the battery from SYS. I recommend doing some tests with only 1x 47uF cap on the SYS pin to see if this issue persists.

    Best regards,

    Alec Lehman

  • 0 in reply to Alec Lehman
    Mastermind 6140 points

    Dear Alec,

    Thank you for your support.

    I will test with just 1 X 47uF cap.

    And here are 2 more questions ;

    1. You said about push button and there is possibility that something is pulling TS/MR pin low during assembly.

    -> Is there no possibility to enter Factory Mode If I add push button? (and not insert it on PCB because my customer do not use factory mode)

    2. If \CE pin is always low, BQ25185 cannot enter Factory Mode and always make SYS output?

    Please check this issue. Thanks.

    Best regards,

    Chase 

  • +1 in reply to Chase Jeong
    TI__Expert 3525 points

    Hello Chase,

    Chase Jeong said:

    1. You said about push button and there is possibility that something is pulling TS/MR pin low during assembly.

    -> Is there no possibility to enter Factory Mode If I add push button? (and not insert it on PCB because my customer do not use factory mode)

    The device will enter factory mode when the adapter is removed after the TS/MR pin is held low for a duration of tLPRESS with the adapter initially present for this duration. This will happen regardless of whether the TS/MR pin is held low by a push button press or an unintended action during assembly. Therefore, it should not be necessary to add a push button to prevent this issue from occurring.

    Chase Jeong said:
    2. If \CE pin is always low, BQ25185 cannot enter Factory Mode and always make SYS output?

    The BQ25185 can enter factory mode whether /CE is high or low.

    Please let me know if this issue persists when testing with 1x 47uF cap on SYS.

    Best regards,

    Alec Lehman

  • 0 in reply to Chase Jeong
    TI__Expert 3525 points

    Hello Chase,

    I just wanted to check in and see if you were able to resolve this issue. Please feel free to reach out.

    Best regards,

    Alec Lehman

  • 0 in reply to Alec Lehman
    Mastermind 6140 points

    Dear Alec,

    Thank you for your support, and sorry for the late reply.

    My customer did not check it yet due to other issues. I requested it again, and post another thread if I have more question.

    Best regards,

    Chase