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BQ51003: Calculations of C1 and C2 and usage in EVM

Prodigy 245 points

Replies: 8

Views: 5847

Part Number: BQ51003

Hello,

I am designing a receiver module using BQ51003 IC and want to test the same with an A11 design A2511 charger pad by Powerport Qi.

I want to test the compatibility between coils, receiver, and transmitter modules for efficiency using the BQ51003EVM-764 board.

As a part of designing, I must calculate the resonant capacitors (C1 and C2) using Ls and Ls'.

My question is, is there any test fixture readily available with PC44 shield and spacers so that I calculate Ls and Ls' for C1 and C2?

Also, even after the calculations of C1 and C2, I wonder how do I use these capacitances in EVM, as these values are fixed to 183nF and 1900pF respectively.

If I am not wrong, I will be getting calculating different C1 and C2 values for different coils.

Thank you in advance,

Best Regards,

Srujana Patel.

  • Srujana,

    As per WPC (Qi) specification, the Rx tuning caps are selected based on the Ls and Ls' values measured on a WPC defined reference fixture described in the bq51003 datasheet. Everytime there is a change on the RX system design (Coil, distance from coil to outer surface, distance from the coil to any board components, etc) the C1 and C2 need to be re-calculated since any of these will affect the effective inductance (Ls') of the receiver coil. So yes, you will get different C1 and C2 values with different receiver coils.

    If you want, for example, to test different receiver coils using the EVM, you will need to replace the coil in the EVM casing, place the EVM on the test fixture and measure the effective inductance of the coil (LS'). You will also need to measure inductance whne the EVM is not on the fixture (LS). Once you calculate the values for C1 and C2 based on the measurements you will need to replace the caps in the EVM.

    I am not aware of a commercially available test fixture, but will check.
  • In reply to Norelis Medina:

    Hello Norelis,

    Thank you so much for the reply. 

    My doubt is, can these capacitances be replaced with calculated capacitors in the EVM?

    I haven't bought it yet and hence have no idea of how it shall work. 

    Thank you for your support.

    Regards,

    Srujana Patel.

  • In reply to Srujana Patel:

    Srujana.

    You may be able to desolder the capacitors from the EVM and replace them with capacitors with the calculated values.

  • In reply to Norelis Medina:

    Hello Norelis,

    Thank you so much for the answer.
    I shall follow it.
  • In reply to Srujana Patel:

    Hello Norelis,


    I want to design a receiver module with BQ51003 IC for a transmitter from powerport Qi (Model - A2511 of A5 or A11 reference design).

    My doubt is, Are these both models compatible with each other?

    I am using coils of TX - 30mm, and RX - 18mm as I want to decrease the size of the equipment.

    This BQ51003 seem to be completely integrated and I believe there is no need to program it.

    Also, I would like to tune the circuit using resonant capacitors (C1 and C2 from BQ51003 spec.).

    My doubt is, As I get to change the capacitances one to two times in the entire project work, Can I buy a TIDA-00318 instead of BQ51003EVM-764?

    Also, Do I need to change any other components (like RILIM or any other resistors or capacitors) in the Receiver side circuit every time I change the coil?



    Thank you in advance.

  • In reply to Srujana Patel:

    Hi Srujana
    Norelis was helping with the forum last week, may thanks for the assistance.

    Qi certified Receiver and Transmitter will operate together. A bq51003 based design receiver can be Qi certified. Certified devices have been tested to standard and will display the Qi logo. A number of device on the market will say Qi compatible and this often means not Qi certified or tested to Qi standards.
    You would check your proposed transmitter for the above to determine if it would work with bq51003.

    "I am using coils of TX - 30mm, and RX - 18mm as I want to decrease the size of the equipment." --Bill J-I have tested this size TX and RX coil together with good results. Note 30mm TX coil is not Qi certifiable.

    "This BQ51003 seem to be completely integrated and I believe there is no need to program it."---Bill J-Yes this is correct

    "Also, Do I need to change any other components (like RILIM or any other resistors or capacitors) in the Receiver side circuit every time I change the coil?"----Bill J-Coil tuning will change with RX coil and physical changes around the coil, see data sheet Ls' info. C1 and C2 would need to change when Ls' changes. But RILIM would not change.

    "Also, I would like to tune the circuit using resonant capacitors (C1 and C2 from BQ51003 spec.)."---Bill J - This can be done see data sheet C1, C2 and Ls'.

    Best Regards,

    Bill Johns,  Applications Engineer

    Texas Instruments Inc

    Dallas, Texas

    For more information on Battery Charger Solutions see Link

    Search "FAQ" on E2E Forum for common questions on battery charger solutions. 

  • In reply to Bill Johns:

    Hello Mr. Johns,

    Thank you so much the response. That information is precise and helpful.

    But, I am afraid you missed out one more question. 

    The question is "I found TIDA-00318 as a product using BQ51003 receiver IC. As I need to just change the resonant capacitances in every iteration of testing. Can I purchase and test with TIDA-00318 instead of BQ51003EVM-764?"

    Also to mention, I do not plan to design a Qi certified model, but a Qi compatible model. And, my transmitter module is not just Qi compatible but not Qi certified. 

    So, how sure can I be that the transmitter and BQ51003 are compatible with each other? Otherwise, I shall use BQ500212A transmitter module.

    Please let me know what module can I buy (like TIDA-00318 for BQ51003). 

    Also, do I need to change any components on the transmitter side when I change the coils?

    Thank you in advance,

    Best Regards,

    Srujana Patel.

  • In reply to Srujana Patel:

    Hello
    We provide design files for TIDA designs but they are not available for purchase.

    Best Regards,

    Bill Johns,  Applications Engineer

    Texas Instruments Inc

    Dallas, Texas

    For more information on Battery Charger Solutions see Link

    Search "FAQ" on E2E Forum for common questions on battery charger solutions. 

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