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BQ51025: wireless power RX chip BQ51025YFPR damaged

Mobydata - Tony Liu
Intellectual 265 points
Part Number: BQ51025

After few insertions, including insertions made with various angles (+45°, -45°, 90°), the wireless power Rx block can't work. 

the VAC voltage is set 9.6V.

after damage, the VAC voltage is only about 700mV

  • 0
    TI__Guru* 75806 points
    I will contact you and we can work on this problem off line.
  • 0 in reply to Bill Johns
    TI__Guru* 75806 points

    The bq51025 has input over voltage protection that will protect against voltage transients that could damage device.  

    A typical situation that will cause a voltage transient is moved the RX coil (phone) from a position of poor coupling to a position of good coupling the input voltage will increase and Clamp1 / Clamp2 will be needed to protect the device.  This could be a case where the customer is picking up the phone slowly and then drops it.  The field will increase to compensate for the increasing distance then when dropped the larger field will generate a large input voltage requiring the clamp circuit.

     Clamp circuit should trip when rectifier voltage reaches about 15.1V. The Clamp1 & 2 mosfets will turn on connecting capacitors to the AC lines adding load and reduce input voltage.  Also during this time the RX is sending commands to TX reducing  the operating voltage.  

    When trouble shooting this type of problem check the voltage at RECT. 

    Possible problems with the clamp circuit will be using small or low voltage rated clamp capacitors.  Higher ESR will reduce effectiveness of the clamp circuit.

     

  • 0 in reply to Bill Johns
    Intellectual 265 points
    Hi Bill,

    tks a lot for your support.

    now, we use the clamp is below:
    C2003,C2008 Capacitor0603 470nF±10% X5R 25V 电容0603 470nF±10% X5R 25V YAGEO CC0603KRX5R8BB474
    it is same specification as that in EVM board.
    we need use more lower voltage rating capacitor?
  • 0 in reply to Mobydata - Tony Liu
    TI__Guru* 75806 points
    Hello
    The capacitors are OK.

    The schematic shows a connections between FOD pin F2 and Q2003 that does not look correct. If Q2003 is turned on it can cause problems with FOD and current limit. Can you the review the circuit, what is the plans for Q2000 and Q2003.

    You can contact me off line.
  • 0 in reply to Bill Johns
    Intellectual 265 points
    yes, there is mistake on shcematic design, but even if we remove the MOSFET Q2003, Q2000, and R2013, the change the R2012 to 53K, find that teh issue still exist, damage the RX chip,
  • 0 in reply to Mobydata - Tony Liu
    TI__Guru* 75806 points
    Hello
    Somethings to check:
    1.) Voltage at RECT for overshoot, this should be in the 15 to 16V range when clamp circuit is active.
    2.) What RX coil are you using for this application and is it tuned
    3.) What TX is used for this test?
  • 0 in reply to Bill Johns
    Intellectual 265 points

    Hi Bill,

    2.) What RX coil are you using for this application and is it tuned
    <TONY>: customized RX coil , the parameter is L=~15.4uH@130Khz, Rs = 153mohm@130Khz, Q=81
    3.) What TX is used for this test?
    <TONY>: TX product is also designed by us. COIL is type A29

    BRS,
    TONY LIU

  • 0 in reply to Mobydata - Tony Liu
    Intellectual 265 points

    Hi,

    attach the PCB layout file, could you please help check it?

    Bill J -- I have down loaded the file

    BRS,

    TONY LIU