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BQ51013B: BQ51013B lost connection with Qi TX when current reduce rapidly

Chao Chen84
Prodigy 20 points
Part Number: BQ51013B

Hi All, 

we used the BQ51013B for a 8.4V two serial connected battery for charge.

when the battery close to full, the charging current is reduced from 880mA to 80mA around. in this case, the RX shut off the output and restart again and again.

The attached was the schematic of the design.

wireless charger rev.pdf

  • 0
    TI__Guru* 75606 points
    Hello
    A couple of things to look at:
    1.) Is the coil tuning OK -- Measure Coil L in case on TX and used this value to tune C19, C30 and C42 to 100kHz. -- Coil L value (6.3uH) looks low, is this right?
    2.) Adjust the COMM 1 / 2 capacitor value to about 10% of C19, C30 and C42.
    3.) Does position of the RX Coil change this drop out at 80mA, decrease the coil to coil distance or better centering of the coils. -- What is current coil to coil distance?
    4.) Take a look at RECT pin and check the Comm Packet behavior. My thinking is the communication is having problems at light loads.
  • 0 in reply to Bill Johns
    TI__Guru* 75606 points
    Hello
    Any update on this question?
  • 0 in reply to Bill Johns
    Prodigy 20 points

    Hi Johns,

    Thanks for your reply.

    We already solved it. but the actual problem is not the problem of the BQ51013B. it's the booster convert for the battery charge issue. it caused the restart of the Qi TX/RX part.

    Anyway, thanks.