FOD on STWBC-MC

[SvenRaecker]

Hello STM community.

We developed a wireless charger based on the STWBC-MC chip.

Our design follows exactly the ST Eval-Kit STEVAL-ISB047V1.

No we are facing a problem with a customer, that the Foreign Object Detection (FOD) does not work stable. In some cases the charger does not detect foreign objects and still transfers power, wich resulted in one case to an overheating of the charging surface (deformation, melting marks and smell).

Is there a chance to improve the FOD by tuning the parameters (see picture below)? The description of the parameters is unclear for us and does not help. How can we evaluate proper parameters?

Thanks in advance,

Sven.

[willzhou]

Hi

please check this document to change fod setting.

BTW our wireless charge product have updated.

https://www.st.com/content/ccc/resource/technical/document/user_manual/group1/a2/fc/ce/c3/9f/e4/40/8a/DM00550209/files/DM00550209.pdf/jcr:content/translations/en.DM00550209.pdf

https://www.st.com/en/power-management/stwbc2-hp.html

[SvenRaecker]

Thanks for you answer.

I know this document. Section 5.2.2 describes the QFOD calibration procedure (Test 2").

But additionally I'd like to understand, what the parameters in the registry settings are used for. Is there a chance to adjust the FOD performance/sensitivity? The registry description does not help to understand it.

In the "Test" menu, there is also a "FOD metrics" function. 

I understand that, if the FOD margin goes under 0, the FOD is active and turns of charging. But what are the other parameters? Can I use that to evaluate a proper FOD sensitivity.

Our application uses different coversheets between the charging surface and the smartphone. I understand that this requires a tuning to adjust the FOD.

Thanks and best regards, Sven.

[willzhou]

Hi

If your application uses different coversheets, please use the worse coversheets, for example maximum thickness coversheets, use GUI and Section 5.2.2 to do QFOD calibration.