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BQ51013B: Communication/Failure to operate on charging pads that the BQ51013A worked with

David Guest1
Intellectual 350 points
Part Number: BQ51013B
Other Parts Discussed in Thread: BQ51013A,

We have been using the BQ51013A in our product (500 qty) - no problem.

Changed to the BQ51013B and we are having lots of support issues with failures to work of some wiirless charging pads , including reputable names such as Belkin and Samsung.

I am suspecting its the enhancement to WPC1.2  - Is their anyway to disable this feature on the chip.

  • 0
    TI__Guru* 75896 points

    Hello

    BQ51013A is built to comply with WPC 1.0 standard and 13B with WPC 1.2.  The device will identify itself to TX as 1.0 or 1.2 at start up.

    In the 1.2 standard Foreign Object Detection (FOD) is added. 

    Once the RX identifies itself as 1.2 to the TX it will begin using FOD feature and RX must accurately report received power.  Cannot turn off the feature but the FOD setting can be adjusted so that it is less likely to trip FOD.

    How likely is a metal object to be placed between TX and RX coil?

    What is your output power?

    How large is the RX coil?

  • 0 in reply to Bill Johns
    Intellectual 350 points

    The output power is 1A into a TI charger chip -BQ24092DGQR.

    The coil is 30mm x 40mm (identical to one you recommend in app note).

    Metal object - highly unlikely.

    There appeared a shortage on the A part, so we naturally migrated to the newer part B  (thought the A was being discontinued).

    I think its down to the comms between the Chip and the Charging pad - as some pads (even cheap ones ) work whilst other reputable ones don't.

    We have just bought a 100 fast charge pads from China at just over a $1 each and they work well and take 1.2A whilst charging battery at around 1A (set by BQ24092DGQR )

  • 0 in reply to David Guest1
    TI__Guru* 75896 points

    Thanks for the reply

    Comm circuit did not change between 13A and 13B. A test would be to increase the COMM1 / 2 value, typical is 22nF but could be increased to 47nF.

    My first suspect is the FOD circuit.  A test would be to increase R-FOD value, FOD pin to ground.  Value of ILIM to FOD resistor (R1) can be decreased.

  • 0 in reply to Bill Johns
    Intellectual 350 points

    Thanks for your reply - yes you were right its the resistor to the FOD changed  it and now works (increased to 220R)

    Might I suggest you put a big warning or note on the datasheet that this resistor value needs to change from a Rev A chip to a Rev B chip - else people will get caught out (like us).

    It should be a note at the start of the datasheet , that there is a difference between Rev A and RevB schematics and Rev B cannot be used in a Rev A design without changes - aka this resistor value.

    But that aside - thanks alot for your help.