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BQ51013B: BQ51013B Vout can not work normally.

Terry Tseng
Expert 1075 points
Part Number: BQ51013B

Dear TI sir :

The Smart phone use BQ51013B.   The Tx device is standard "qi" wireless power.

TEST CONDITIONS : Put the Smart phone on the "qi" Tx device.

BQ51013B Vout  of the Smart phone work normally at standby mode. 

BQ51013B Vout  of the Smart phone can not work normally at operation mode. For example : browse picture, internet, play app game...

We check BQ51013B EN1 EN2, always keep "Low"  And I measure the waveform of BQ51013B Out & RECT.

Below is Out. You can see BQ51013B Vout drop after 1s.

Below is RECT.

Please help to check this problem.

Thanks!

  • 0
    TI__Guru* 75606 points
    This type of behavior can be caused by several problems, TX coil to RX coil spacing, RX coil tuning are some.
    Could you send schematic on the RX and info on the RX coil?
  • 0 in reply to Bill Johns
    Expert 1075 points

    Dear Sir

    I think it is not about TX coil to RX coil spacing.

    BQ51013B Vout  of the Smart phone work normally at standby mode. 

    BQ51013B Vout  of the Smart phone can not work normally at operation mode.

    Both test condition is the same.

    Attached file is schematic.

    2CX003_V1.04_DL(161028).pdf

  • 0 in reply to Terry Tseng
    TI__Guru* 75606 points
    Hello
    Thanks for the schematic, I have reviewed it and do not see any problems.
    The RX coil tuning (C2331, C2330 and C2332) is 300nF, this would indicate the Ls' value of the coil is about 8.5uH. Is this correct?
    What is coil physical size and distance from the TX coil?

    Is Standby mode a no load condition without battery charging?
  • 0 in reply to Bill Johns
    Expert 1075 points

    Hi Sir :

    I will confirm how much uH of coil.

    Standby mode : Smart phone turn on and do nothing.   Put phone on the Qi Rx then battery is charging.

    Below is FOD waveform.   FOD voltage is 0.43V in normal.     FOD voltage goes to Low  (0V) in abnormal.  

  • 0 in reply to Terry Tseng
    TI__Guru* 75606 points
    Hello
    RX FOD is a measure of the output current and will represent power received by the RX. The current at ILIIM is output current and is sampled by FOD pin. This is then converted into a digital word and set to the TX for FOD.
    The FOD function needs to be calibrated.
    As a quick check the FOD resistor can be increased in value to prevent FOD fault. Output current limit is set by ILIM to ground resistance. If FOD resistor is increased, ILIM to FOD resistor can be decreased to keep current limit the same.
  • 0 in reply to Bill Johns
    Expert 1075 points
    Dear Sir :
    Could you tell me how to calibrate FOD function.
    Now RLIM = 110 ohm, RFOD = 180 ohm

    And I check my customer, Ls' value of the coil is 8.7~9.62uH@100KHz
    How about the RX coil tuning (C2331, C2330 and C2332) is 300nF, is it all right ?
  • 0 in reply to Terry Tseng
    TI__Guru* 75606 points
    Hello
    For Ls' value of 8.5uH 300nF is about right and 8.7 to 9.62uH will put the tuning freq a little low, see section 8.2.1.2.2 in data sheet.

    For FOD tuning see:
    www.ti.com/lit/zip/sluc577