110khz resonant freq of NXQ1TXH5

[JbaleAlfa]

Hi

For the wireless power chip NXQ1TXH5 it state to tune the resonant frequency of the LC tank so that its close to but no exceeding 110KHz

First of, Why is it important not to go over 110KHz ?

Secondly, If the resonant frequency is set to 115KHz would this cause any problems that may cause a fault in the NXQ1TXH5?

Regards Joe

[diazmarin09]

Hello Joe,

I hope all is great with you. Thank you for using the NXP communities.

According to Wireless Power Consortium (WPC) Qi specification (Ref. 1), values have been specified for both the inductance (Lp) and the capacitance (Cp) in the resonant tank.

The assembly of the inductor coil and the shielding and accessories must have an inductance (Lp) of 6.3 uH (about 10 %). The capacitance (Cp) of the series capacitor must be 0.4 uF (about 5 %). The input voltage to the full-bridge inverter must be 5 V (about 5 %). The combination of Lp and Cp is intended to give the tank a target resonant frequency of:

Therefore, such values are based on the specification. under various conditions, tuning the resonant tank to perform optimally can be an option.

Please find further information on the document below:

AN11775 - NXQ1TXH5/101 one-chip 5 V Qi wireless transmitter

I hope this information helps.

Regards,

David

[JbaleAlfa]

Just to confirm the 110khz it set by WPC, and having a resonant frequency of 115Khz wont be harmful to the NXQ1TXH5, as I have notice that in the app note that the demo circuit has a Cp 364nF compared to the suggested 400nF of the WPC spec?

Regards Joe

[diazmarin09]

Hello Joe,

Once again, thank you for using the NXP community.

You are correct. In order to comply with the specification, such values are recommended.

Personally, I do not see any problems with 115kHz. Anyway, I do recommend to perform your own tests as we do not have such frequency characterized.

I hope this information helps.

Regards,

David

[JbaleAlfa · Accepted solution]

Hello David 

Thank you you information is helpful

Regards Joe