NXQ1TXH5 2.5uH coil won't trigger charge

[tomsema]

Dear NXP,

We've been developing a PCB for mass production based on the reference schematic. Due to size constraints we've been experimenting with the following coil:

http://www.farnell.com/datasheets/2706721.pdf?_ga=2.202782551.793647931.1588784884-1018318154.158739... 

which is a 2.5uH coil  different from the 6.3uH from the reference schematic. I adjusted the series capacitance to 1uF to match the resonant-frequency of +- 109KHz which should be enough. Unfortunately this doesn't seem to work. Could you help me understand why this isn't working? I'm aware that there are other 6.3uH coils that I can use but I can't get my head around this. 

Kind regards,

Reinier 

[tomsema]

Hi G.w. Sun,

Thanks for your quick reply. I read the AN11775 datasheet and noticed that they're referring to external documentation regarding FOD. 

"

Details about FOD configuration can be found in the NXQ1TXH5/101 FOD configuration document (Ref. 4). This document is available through your NXP sales representative."

Could you provide me with documentation on how to properly configure FOD?

Regards,

Reinier

[guoweisun]

Already send to you!

[guoweisun]

NXP EVB describes the NXQ1TXH5/101 wireless charger solution designed
for A11 Qi coils，but this Single-chip WPC 1.2 Qi-compliant device for A5/A11/A12/A16 5 V single-coil
low-power transmitter.

If L is changed, the value of R8 must be adapted to get the right value for FOD_E.

For more detail please read AN11775.