• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 64 subscribers
  • Views 1059 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ51050B: FOD Calibration

Glenn Herb
Prodigy 45 points
Part Number: BQ51050B
Other Parts Discussed in Thread: BQ51013B,

Hi,

We are designing a medical wearable that will use wireless charging. Due to size constraints, your BQ51050B Wireless Power Receiver and Battery Charger appears to be the perfect choice for this design since it is a one chip solution. I have acquired your BQ51050BEVM and have run preliminary breadboard testing and it appears to work well. I have just started to look at FOD calibration and have run into some issues. I downloaded your FODCalibration.exe program and installed it on my computer. To test it before taking my own data, I tried to run it with the supplied “Real Calibration Example.txt” file. As instructed, I set the Part # to BQ51013B and loaded the example file and pressed Next. On the Vos Calibration page, I was able to get a reasonable model graph by changing the Vos field, but on the next page, RFOD/Ros Tuning, the program was completely unresponsive to changes in the Ros value. If upon entering the page I first adjusted the RFOD value, the graph was responsive. But after I attempted to make any change to the Ros value, the graph was no longer responsive, even if I then went back and changed the RFOD value.

To see if this was a Windows 10 issue, I then installed the program onto a Windows 7 machine, but the behavior was identical. Do you know why this is not working?

If the program doesn’t work, I could try to calculate the values manually. Since your documentation gives no information at all about calculating the Rfod and Ros resistors, can you provide any help in the way of equations and a more detailed description of the FOD/resistor divider operation so I can manually calculate and adjust the values based on obtained data?

Also, we don't need Qi qualification on this product but it would be good if it worked with most Qi chargers.  So if there was a way to "maximize" the FOD tolerance so it wouldn't "get in the way" of a successful charging session, that would be useful.  Again, from a design standpoint, it would be good to have some documentation that explained the FOD operation in the BQ51050B and the setting resistors calculation requirements.


Thanks,

Glenn


  • 0
    TI__Guru* 75656 points

    Hello Glenn

    If you do not need Qi certification a rough FOD Calibration will work. 

    This can be done with a transmitter that can read power transmitted by the TX (PPT) and power reported by the receiver (PPR) you can do a rough calibration.  In the procedure the AVID FOD TX, it will accurately measure PPT.  But many transmitters provide PPT at reduced accuracy.  

    If your application is lower power (less than 2.5W).  Or a simple loss profile, not much metal around the coil and loss is flat in all 5 positions. The Excel spread sheet may be overkill,   Graph the loss vs output power at the center position, it should be between 0 and -300mW.  Adjust Ros and Rfod as needed.  Ros will have a larger impact on loss at low power while Rfod will have a large impact on higher power. 

    Note that loss is the difference between PPT and PPR, the RX will always over report power received resulting in a negative loss number. 

    If the application is not going to need FOD protection, chances of something getting between TX and RX slim due to industrial design. The target value for loss increased (more neg)  to -300mW to -600mW.

  • 0 in reply to Bill Johns
    Prodigy 45 points


    Hi Bill

    Thanks for your response on this.  To your points, we don’t need Qi certification, it is a low power application (< 1.5W), and we will likely not need FOD protection.

    We don’t need the precision (and can’t justify the cost) of the AVID unit.  You mentioned you are aware of other transmitters/chargers that provide PPT and PPR data at reduced accuracy and cost.  Can you recommend a few that we can look at?

    You also mentioned a spread sheet.  The only tool I have found on the BQ51050B tools and documentation pages is the FODCalibration.exe program which, as I mentioned, does not seem to work properly.  Where can I find the spread sheet you spoke about?

    Finally, you said to “adjust Ros and Rfod as needed”, but I can find no equations or spread sheets that show how to adjust those two resistors to achieve the desired result.  Can you provide the equations to adjust the resistors based on the application and acquired data.


    Thanks,

    Glenn



  • 0 in reply to Glenn Herb
    TI__Guru* 75656 points

    Hi Glenn

    Sorry for the delay, will get you more info on other TX.  Low power and non-Qi is good.

    What do you think the risk of getting a metal object between TX and RX would be in your design?

    What can you tell me about your schedule and volumes?

  • 0 in reply to Bill Johns
    Prodigy 45 points

    Hi Bill,

    The probability of getting a foreign object in the charging path is reasonably low. 

    This project is a spin-off of a consumer wearable.  This version is targeted more at the research market (more sensors and, of course, no more board area), so its volumes are much lower than its "cousin".  Marketing hasn't shared a great deal of volume estimates, but I would guess we're talking about less than 1K units per year.  We're going into prototype in a few weeks and release to production is scheduled for 1st Qtr 2021.

    I'm looking forward to your TX device suggestions and your equations / spreadsheet references.

    Thanks,

    Glenn

  • 0 in reply to Glenn Herb
    TI__Guru* 75656 points

    Hi Glenn

    I will send you a private e message will more info on transmitters.