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Inquiries regarding bq51013B schematics

Atsushi Okui
Genius 4015 points
Other Parts Discussed in Thread: BQ51013B, BQ51013, BQ500211, BQ500211A

Hello, all

Now we are designing our own board with bq51013B. Then would like to know the detail of some components based on application schematics. Please refer to the items below, and feedback us with your comment.

1) RFOD

On page 10 of this datasheet (SLUSB62), this seems to be fixed to 188ohm based on the description "Connect to GND with a 188 Ω resistor.".

Meanwhile, when referring the schematic of bq51013xEVM-764 (SLUUA44), this value is selectable either 150ohm or 196ohm. (R2 value on Figure1, page 3)

Please let us clarify which hardware register value should be applied on actual system configuration.

2) CCOMM1 and CCOMM2

On page 24 of the datasheet, these value should be 22nF based on the description "In this case, a capacitor is connected from COM1 to AC1 and from COM2 to AC2. When the COMM switches are closed there is effectively a 22 nF capacitor connected between AC1 and AC2." Also these values are applied on the schematic of bq51013xEVM-764.

Meanwhile, when referring Figure 36 on datasheet page 25, these values seem to be fixed to 47nF.

Please let us clarify which capacitance value should be applied as well. 

 If you have some guidelines on these matter above, please let us know.

We thank you in advance for your information. 

Best regards,

  • 0
    Prodigy 80 points

    Hi,

    I also have similar doubts on these

  • 0 in reply to Vikram Chandrasekaran1
    TI__Genius 14890 points

    Vikram,

    Do you have a specific question on your application that I can assist with?

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 80 points

    Hi Dick,

    I am testing a board creating components as similar to the BQ51013 EVM for rx and BQ500211 is the tx chip with components same as the EVM of it.

    I am using wurth coils 760308111 for tx and 760308201 for rx as recommonded in datasheet.

    I am able to see communication between tx and rx coils in the scope. But my OUT at the RX doesn't appear as 5V.

    Can you please help me solving this.

     

     

  • 0 in reply to Vikram Chandrasekaran1
    TI__Genius 14890 points

    Vikram,

    Would you be able to send a schematic of the wireless circuitry that we could review?  Can you tell me the voltage at the RECT pin?  A scope picture of the RECT pin when startup begins and during communication would be helpful.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 80 points

    Hi Dick,

    My transmitter part is working fine as i tested with Qi compatible phone.

    Attached is my receiver section schematics and snapshot when I probe at the RECT and RX coils terminals when placed on my transmitter coil.

    The coil used is one of the recommended coil from RX EVM.

     At the RECT terminal

    At the RX coil  

  • 0 in reply to Vikram Chandrasekaran1
    TI__Genius 14890 points

    Vikram,

    The schematic looks good.  The only concern I see is the value of the value of the resonant capacitors (C62-C66).  I expect you chose those to match the EVM since the coil is also from the EVM.  Have you measured the Ls and Ls' to verify everything is still correct.

    There is an excellent application note that can help with your coil / system design "Designing a Q-compliant receiver coil for wireless power systems".  The link is below.

    http://www.ti.com/analog/docs/litabsmultiplefilelist.tsp?literatureNumber=slyt479&docCategoryId=1&familyId=64

    Looking at you plots, I see that the Rx coil only gets to ~800mV.  That shows there is not enough coupling to get things moving.  This could be many reasons with the most common being the spacing between the Tx coil and the Rx coil and the X/Y alignment between the coils.  Also, what can you tell me about the shielding on both coils?

    The image below shows the process during a valid Rx being placed on a Tx.

    This plot shows the normal operation of the Rx on startup.  You can see 2 analog pings (on the Tx coil) that occur before the Rx is placed on the Tx.  The 1st analog ping that occurs after the Rx is placed on the Tx begins the startup process.

    When looking at the Rx coil during the ping,  you should also see a signal much greater than what you have seen.  The image below shows a ping on a coil (No EVM, just the coil) when the coil is placed on a bq500211A (5V) EVM.

    If you don't get something like this (note the amplitude), the your alignment is off (X, Y or Z direction). 

    Regards,

    Dick