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Some questions related to adapting the TIDA-00669 reference design

Sebastian Jentschke
Prodigy 90 points
Other Parts Discussed in Thread: CC3220MODA, TIDA-00669, TPS63051, TPS63001, BQ51050B

Hi,

I have designed a PCB, derived from the TIDA-00669, for inductive charging functionality, battery management and the acquisition of physiological data  using the analogue pins on the CC3220MODA.

A have a couple of questions:
[1] I would like to allow for a higher current flow (1500 mA), therefore I adjusted the Rs to ILIM to 9 (originally 200) Ohm and replaced the TPS63051 with the TPS63001. Have further changes to be made?
[2] If we want to cut off the power supply while charging and use the nCHG output on the BQ51050B to switch on / off a TPS63001 via the EN pin, do we have to use a pull-up-resistor or can we connect it directly?
[3] If we use the CC3220MODA on the same board with the power supply and the inductive charging what are the implications, especially with respect to ground planes?

Thank you very much,

Sebastian

  • 0
    TI__Expert 8870 points

    Sebastian,

        The TIDA-00669 is a great starting point for any wireless charger design. A lot went into making this reference design complete and fully operational. Your changes are simple and straight forward, with the first question being your most difficult change. It's not difficult from a " hard to do" solution but difficult from a " need to change a few parts that will require knowledge and testing to verify Qi compliance and operations" stand point.

    1) Yes, you will need to change the coil to get 1.5A. Changing the coil will also mean changing the series and parallel capacitors attached to the coil. Which will mean testing and verification that the system will meet the Qi standard with these changes. Meeting the Qi standard is important, because it means that you will meet the FCC requirements as well as operating correctly with Qi Transmitters (compatibility). 

      Take a look at these docs.

    http://www.ti.com/lit/pdf/slua724

    http://www.ti.com/lit/pdf/sluua25

    www.ti.com/.../getliterature.tsp Qi inductor design guide&tisearch=Search-EN-TechDocs

    I wont be able to help you with this process, however TI has a lot of documents on this, as well as there are a lot of coil manufactures that have off the shelf coils with documentation on how to design them in. Check Digi-Key and Mouser for the coils.  

    2) Yes you will need a pull up resistor. The output of the /CHG pin is "Open-drain output – active when BAT is enabled. Float if not used."

    3) simply the wireless charging coil will need and is required to have a ferrite shield between the coil and the circuit board. This is to reduce radiate emissions as well as control the inductance of the coil. The shield will also focus the TX energy on the RX coil giving you higher current than if you did not have the ferrite shield. When designed correctly using the CC3220MODA with this circuit will not be a problem. The ground plane is common for the circuits and the coil is differential with the shield so the EMI from the coil will not be a problem for the RF circuit. (Note: With out the ferrite shield the RF circuit will not operate correctly) 

    Let me know if you have any other questions.

      

  • 0 in reply to Gordon Varney
    Prodigy 90 points

    Dear Gordon,

    thank you very much for your reply.

    May I follow up a bit on your reply to 1). From the sentence "The coil tested well to 1.5A and is used to 500mA in this booster pack design." (p. 9, tidub31.pdf) I was (maybe incorrectly) assuming that the coil and the current design would tolerate 1.5A. According to the data sheet it (Wuerth 760308103206) has a current rating of 1.55A. What am I doing wrong here and where is my misunderstanding? Is it how the capacitors attached to the coil are selected in the TIDA-00669 what limits the current flow?

    More general for the TIDA-00669 as it is now: Would you say that this design is only suitable for up to 500 mA or up to what current flow would you expect it to tolerate?

    Finally, unfortunately, the third link (getliterature.tsp) did not come through. Could you please post the link again.

    Thank you very much for your help!

    Sebastian

  • 0 in reply to Gordon Varney
    Prodigy 90 points

    I have posted some follow-up questions on October 25th.