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BQ51003: BQ51003

Abdullah Ahmed1
Prodigy 80 points
Part Number: BQ51003

Hello,

I am trying to use BQ51003 with an ideal transmitter which will transmit 1W-2W power at 10MHz frequency as a proof of concept.

I am modifying the resonance tank to e.g. using 1.5uH with a 162pF capacitor connected as parallel between AC1 and AC2. to give resonance at ~10MHz.

I am only interested to see if the VOUT of 5V will be available with a load of 100mA, with proper RILM settings.

Will BQ51003, show me the intended behavior with an Ideal TX ? for now I am not interested to make use of the communication between Rx and Tx.

Appreciate your quick response//

  • 0
    TI__Guru* 75886 points
    Hello
    This will not be possible, freq is too high and need communications with the TX.
    BQ51003 is a Qi based design and will need to communicate with the TX to set operating point. If the TX does not respond to RX commands power transfer will stop. Also the rectifier bridge (AC1/AC2 to RECT) is designed for operation in the 100kHz to 200kHz range and has not been evaluated at 10MHz but problems are highly likely.
  • 0 in reply to Bill Johns
    Prodigy 80 points

    Hello Bill,

    Thanks for the reply. If I am using an ideal transmittter (RF power amplifier) at 10MHz, how will the power transfer stop on Rx side.?

    So you don't believe the rectifier would operate at 10MHz ?

    My interest is to see if I can pull out 70mA of current on VOUT at 10MHz. would you be able to suggest another part from TI which I can use ?

    Regards

    Abdullah

  • 0 in reply to Abdullah Ahmed1
    TI__Guru* 75886 points
    Hello Abdullah
    I have serious doubts that the rectifier section will operate at 10MHz.
    The best approach may be to build a rectifier from discreet parts and use an off the shelf LDO.
  • 0 in reply to Bill Johns
    Prodigy 80 points

    Hello Bill,

    Okay one approach I was thinking, is if I do use separate rectifier, and then connect the rectified voltage node from my rectifier to RECT pin on bg51003, will I be able to get VOUT on bg51003, once RECT voltage is is > 3V i.e. above the UVLO level of BG51003.

    I am trying to avoid any inefficiencies using multiple components. So with my own rectifier operable at 10MHz, if I can connect to RECT pin on bg51003, and make it work will be best..

    Appreciate if you can confirm

    Regards

    Abdullah  

  • 0 in reply to Abdullah Ahmed1
    TI__Guru* 75886 points
    Hi
    This would not be good, external rectifier feeding BQ51003. You would only be using the LDO in 003, off the shelf LDO would be better solution.
    Also you can feed DC into the AC1 and AC2, better that trying to power the RECT pin.
  • 0 in reply to Bill Johns
    Prodigy 80 points
    Hello Bill,
    So can I feed directly my rectifier +Ve voltage to AC1, and the negative voltage (ground) to the AC2 pin of the BG51003 ? I understand that I am only using the LDO from the 51003. This provides me a constant 5V output which is what I am looking for.. Regards Abdulalh
  • 0 in reply to Abdullah Ahmed1
    TI__Guru* 75886 points
    Yes can feed rectifier output to AC1/AC2, bridge will work out the polarity. But then you have the other problem of communications RX to TX and the LDO will not turn on unless the TX is following commands from RX.
  • 0 in reply to Bill Johns
    Prodigy 80 points
    Well, I am thinking as long as the rectifier voltage into 51003 is > 3V, the LDo output should turn on..with constant Tx from RF power amplifier I will be using ?

    Regards
    Abdullah
  • 0 in reply to Abdullah Ahmed1
    Prodigy 80 points
    I will keeto EN1 and En2 low so with ideal Tx RF power amplifier, if RECT is above 3V, the LDO will not turn on?
  • 0 in reply to Abdullah Ahmed1
    TI__Guru* 75886 points
    The RX will start communications with the TX above UVLO but the output voltage will not turn on immediately. The RX needs to adjust operating voltage of the TX to 7V for the RX to turn on LDO, see figure 35 and 36 in data sheet.
  • 0 in reply to Bill Johns
    Prodigy 80 points
    So if I connect my rectifier output to RECT pin of 51003, and using my Rx Power, if I can make sure the RECT pin is > 7V, then LDO should turn on correct ? irrespective of the fact wheter the Rx made the Tx change, or I set the RF power amplifier always above 7V manually...Am I correct in this assumption.

    Thanks for your feedback Bill
    Greatly appreciate
  • 0 in reply to Abdullah Ahmed1
    TI__Guru* 75886 points
    Sorry but no.
    The 7V is to start, no load condition.
    If load increases the voltage needs to go down and RX will command the TX to reduce voltage, will range from 7V to 5V at RECT.
    When the TX does not respond RX will turn off output and re-start.
  • 0 in reply to Bill Johns
    Prodigy 80 points
    Hello Bill,
    The load current increase I am expecting is from 0mA to 25mA max, so in that case, I can manualy adjust the RECT by playing with the RF amplifier such that in loaded conditions, I see 5V at the RF amplifier...so if I do that will the LDO be enabled ..

    Thanks and Regards