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Interchanging chips within an EVM board

Shruti Ganesh
Prodigy 50 points
Other Parts Discussed in Thread: BQ51003, BQ51050B, BQ51013B, BQ500410A

Hey,

Im trying to use a BQ51050B board to produce a 5V, 500mA output. Can I replace the IC by a discrete bq51003 chip? I do not require the battery charging function.

If so, what design changes must I bear in mind? What resistors will I be required to modify? Any suggestions for typical values to start with?

Also, I'm redesigning the receiver coil and I want to know if it is necessary to make Ls and Ls' measurements using the reference transmitter? Or can that be bypassed?

I would also like to know what it means when coil spec states Q @ Freq. Design requirements state Q must be greater than 77 at 1000 kHz. How can I verify this when I buy discrete coils?

Looking forward to your reply. 

Cheers,

Shruti

  • 0
    TI__Expert 7730 points

    Those two devices are pin-to-pin compatible so yes you can replace the bq51050B IC with bq51013B and get the DC output.

    There is only one difference in the pin description: TERM pin in bq51050B is now EN1, so please make sure the pin configuration is correct in your new application.

    The measurement of LS and LS' is used to set the Cs and Cd capacitors. You can start with the EVM value and if the performance is not optimal, you can measure LS and LS' to optimize the configuration.

    You can use equation (7) on pg#31 of the bq51050b datasheet to calculate the Q value of your coil.

    Thanks,

    Wenjia

  • 0 in reply to Wenjia Liu
    Prodigy 50 points

    Thank you Wenjia. Will try this out and get back to you on the results.

    Do I have to change any resistor values when I change the IC chip? As in, how do I determine values to connect R1, R2, R6, RFOD resistors?

    Cheers,
    Shruti

  • 0 in reply to Shruti Ganesh
    TI__Expert 7730 points

    If you are using our EVM, then I don't think you need to change any resistor value.

    If you have your own circuit board, you need to use the FOD tuning tool to determine the FOD circuit value.

    http://www.ti.com/lit/zip/sluc577

    Thanks,

    Wenjia

  • 0 in reply to Wenjia Liu
    Prodigy 50 points

    Thank you Wenjia. 

    I tried charging a 3.7V 200mAh battery with a BQ500410A transmitter and a BQ51050B receiver. The battery doesn't seem to charge at all. 

    Am I missing some other connection? I am able to get a periodic rise and fall in Vrect voltage. It rises upto 4.2V and then drops down 3.2V. 

    Also, the LED D4 seems to be blinking constantly after the connection of the battery. Until then, after the initial communication is established the LED keeps glowing. What could this indicate?

    Thanks much for your help. 

    Cheers,

    Shruti

  • 0 in reply to Shruti Ganesh
    TI__Expert 7730 points
    Hello Shruti,

    Are you using our EVMs for both TX and RX? If not, can you share the schematic? I didn't find D4 in the bq51050B EVM schematic.

    Thanks,
    Wenjia
  • 0 in reply to Wenjia Liu
    Prodigy 50 points

    Hello Wenjia, 

    I'm using TI's EVMs for both TX and RX. 

    TX: BQ500410A

    RX:BQ51050B

    The LED D4 is in the transmitter. 

    The input DC voltage is 12V and 500mA. 

    Cheers,

    Shruti

  • 0 in reply to Shruti Ganesh
    TI__Expert 7730 points

    Hi Shruti,

    I used the same TX and RX EVMs and verified that they can charge normally. I have 12V input connected to TX and 3.7V battery connected to the OUT of RX. Nothing else is needed.

    I tried 100mA, 200mA and 300mA and all of them were pretty stable. Based on my observation, during charging, D4 will keep blinking in a frequency of about 1hz, D3 on the TX board is on all the time, and D1 on the RX board is on all the time. Did you see the same thing?

    I attached a picture of the jumper settings of the RX board, please verify if you have the same connections. Can you send over the waveform of OUT and RECT?

    Thanks,

    Wenjia

  • 0 in reply to Wenjia Liu
    Prodigy 50 points
    Hello Wenjia,

    Thank you so much for your help.

    Yes, the jumper settings are correct. I hadn't been giving 12V to the Tx. We were giving something around 9V.

    The battery seems to be charging just fine. Thanks again!

    Cheers,
    Shruti