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bq51013B: start-up issue

Joris De Beer
Prodigy 80 points
Part Number: BQ51013B

Hello,

I am working with the BQ51013B.

When the receiver is placed on an Qi compliant charger,

the output is not enabled.

The receive coil that is used is the Wurth 760308101214.

The Qi-transmitter is equiped with the Wurth 760308100111.

The current limit in the receiver is set on 1A.

Cs is 100nF, and Cd is 780pF.

This is the RECT signaal when the output is kept to zero:

Sometimes the output is enabled after x cycles:

What could be the cause that the output is not enabled?

Thanks.

Joris

  • 0
    TI__Guru* 75656 points

    TX coil looks good (Wurth 760308100111) 6.3uH 50mm, Qi TX coil.

    RX coil looks good (Wurth 760308101214) 26uH 19mm--good small coil, but do not recommend for 1A too small and DCR too high.

    Cs of 100nF will put the tuning at about 98.8kHz, this is good.

    Thanks for the scope shots.

    When the output turn on voltage collapses, this would suggest that the load is too large or possibly a short on the output.  Other thing it may be is the ILIM is not set right, 1A should be enough.  Double check the connection of resistor between ILIM and FOD.  If you have a resistor between Rect and FOD remove it.

    What is coil to coil distance? 

  • 0 in reply to Bill Johns
    Prodigy 80 points
    Hello Bill,

    Thanks for the advice.
    The coil to coil distance is 3.2 mm.
    In normal conditions the current consumption for the circuit is max. 320mA.

    Best Regards.
    Joris