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BQ24072: Batt charging Issue

Velmurugan Ekambanathan
Prodigy 140 points

Part Number: BQ24072

We are facing battery charging issue with the bQ24072 charger device.
We have made 15 protos, and got the samples from TI.
When the board came from the assembly unit the charging was happening, but over couple days we saw battery is not getting charged in 3 boards. this is tested in our Lab
.And 3 more board got same problem in field  after 1 month.
Would like to know why is this issue happening and how to rectify the same. 
Below table shows one board behavior at various combinations, we see similar issue in the other boards.
 Board status POWER  INPUT Battery Present Vout VBAT Charging LED  POWER Good LED
Pass 5V N 4.4 4.2 N Y
Pass 5V Y 4.4 4.2 Y Y
             
Failure 5V N 3.4 2.46 N Y
Failure 5V 3.636 3.863 3.636 N Y
             
Pass N 3.636 3.636 3.636 N N

One more new issues that we started seeing in the field, this happened in two boards.

 Board status POWER  INPUT Battery Present Vout VBAT Charging LED  POWER Good LED
Fail 5V N 0 0 N Y
Fail 5V Y VBAT 3.8 N Y
  • 0
    TI__Mastermind 21590 points

    Hello,

    The behavior shown below is expected and not a failure. OUT is clamped to 3.4V when the battery is not present. Also, when the battery is not present, the IC goes into battery detection (9.3.5.4). This causes the voltage on BAT to have a square waveform from 0 to VBAT (reg). If you're reading this value with a multimeter, it is possible you'll only see the average value.

     

    For the second failure, can you check the input current and the charging current to ensure that the battery is not charging. Also check to make sure the EN1 and EN2 pins aren't in standby mode (EN1 and EN2 are not equal to 1).

     Regards,

    Raheem

  • 0 in reply to Raheem
    Prodigy 140 points

    Dear Raheem,

    Attached the schematics for your reference.

    EN1 =0 , EN2 = 1

    Case1:

    Board status POWER  INPUT Battery Present Vout VBAT Charging LED POWER Good LED

    Pass                      5V                             N                  4.4 4.2                   N                                  Y

    Pass                      5V                              Y                  4.4 4.2                    Y                                    Y

    Case 1: Status of the working board with us ( Pass)

    Case2:

    Board status POWER  INPUT Battery Present Vout VBAT Charging LED POWER Good LED

    Failure                            5V                   N                          3.4 2.46            N                           Y

    Case 2: also is as per your datasheet.

    Case 3:

    Failure                              5V               Y STG_G_W_V1.pdf                      3.863 3.636      NNNNNN                   Y

    Case 3 is failure, as the battery is not getting charged.

    We are checking with a power supply with a ammeter ( no load condition) , the boards draws no current, that means it is not taking input current and charging current

  • 0 in reply to Velmurugan Ekambanathan
    TI__Mastermind 21590 points
    Hello,
    For Case 3 which failed, the voltages look correct. However, the LEDs look like they dont turn on. Can you try pulling both LEDs to VIN and VBAT?
    Regards,
    Raheem
  • 0 in reply to Raheem
    Prodigy 140 points

    For case 3, the voltage that i mentioned is at Vbat pin, that is the voltage of the battery, and the device is not taking any current from the input.

    That means the device is not charging the battery and the LED indication is correct.

    The other thing is even when the VIn 5V and the Battery is present, these device output si 3.4V, why is this failed device or not detecting the battery.

    I tried pulling up the TD and also Pulling down the TD, result is same.

  • 0 in reply to Velmurugan Ekambanathan
    TI__Mastermind 21590 points
    Hello,
    For the case not getting charged, try reducing the input current by setting the device into USB100 mode (EN1 = EN2 = 0). If the issue persists, toggle /CE and see if charge restarts. Try replacing the board with one that is known to work to make sure there are no issues with the board. If there are still issues, place the failing ICs on boards that work and let me know if anything changes.
    Regards,
    Raheem