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BQ24032A: No Charging with AC Input

Richard Gong21
Prodigy 190 points
Part Number: BQ24032A

Dear TI:

We have received our boards back from our assembly house and some boards function quiet differently.  

Here is the schematic. 

Some boards have the following measurements:

Vdppm = 3.512V

Vtmr = 2.47V

Viset1 = 2.46V

Vout = 4.33V

Some other boards are different (Charging looks like not working):

Vdppm = 4.13V

Vtmr = 0.79V

Viset1 = 0V

Vout = 4.4V

The load is about 100mA. And same AC adapter and battery were used for both cases.

Why the voltages are different on different boards? What could be the issue? Can the LDO be the power to the pull up resistors for CE/ISET2/PSEL?

Thanks,

Richard

  • 0
    TI__Mastermind 21590 points

    Hello RIchard,

    What is the TS voltage on the board which isnt working?

    Can you adjust the DPPM voltage to 3.5 like the working board by reducing the resistor on DPPM.

    LDO is fine as power for pull up resistors.

  • 0 in reply to Raheem
    Prodigy 190 points

    Hello Raheem,

    Thanks for the reply. Vrs was 1.1V for both cases.

    If Rdppm is replaced with 33K, the charging works fine with similar voltages on those pins. Can you please give us the explanations?

    Also, if there was no battery connected, the LED that connects to STAT2 was always ON and the STAT1 LED was blinking. What the LEDs tell us about? And is there a way to stop the blinking?

    Thanks,

    Richard

  • 0 in reply to Richard Gong21
    TI__Mastermind 21590 points

    Hello Richard,

    This will occur if the OUT voltage falls below the DPPM voltage. When charging does not occur, does VOUT drop below 4.13V?

    The LEDs will blink because when the battery is absent, capacitor on VBAT will charge and discharge. This will cause the charger state to go from charging to charge done.

  • 0 in reply to Raheem
    Prodigy 190 points

    The board with charging fine has Vout = 4.33V and the board with no charging has Vout = 4.4V. In my test cases, the Vout was never below 4.13V. Is it normal Vout = 4.33V with AC charging?

    On DPPM pin, what voltage am I supposed to see, VDPPM-SET or VDPPM-REG? 

    Thanks,

    Richard

  • 0 in reply to Richard Gong21
    TI__Mastermind 21590 points

    Hello Richard,

    It is possible to get a bit lower than 4.33V on OUT due to battery and load current causing a drop across the input FET.

    What you see on DPPM will be the VDPPM-SET

  • 0 in reply to Raheem
    Prodigy 190 points

    Hello Raheem,

    Thank you very much for the answers. However, I still don't understand the cause to the issue.

    Here are the configurations and observations.

    1. The charging current was set to 500mA. The system load current was about 100mA. The AC adapter is rated as 2A and it is good enough to provide the charging current and the system load current simultaneously. So the charger should not stop the charging to maintain system current requirements. 

    2. Rdppm = 37.4K to set VDPPM-REG to 4.26V and Vout was 4.4V. So Vout is higher than VDPPM-REG then the charger should not stop the charging.

    3. If Rdppm was changed to 33K, the charging worked fine. Why is that? Any explanations?

    4. We have seen several boards with Rdppm = 37.4K worked fine with AC charging. Then what could cause the variation?

    Thanks,

    Richard

  • 0 in reply to Richard Gong21
    TI__Mastermind 21590 points

    Hello,

    The VDPPM voltage depends on the IDPPM current and the scale factor. Both of these parameters have variance which could cause them to be as high as the maximum values stated in the datasheet. This could be the reason why you have the device entering DPPM when the VDPPM is set to 4.26V which could be close to 4.4V with unit to unit variance.