we have developed our wireless charger based on NXQ1TXH5 following AN11775 and it works perfectly with coil WT-505090-10K2-A11-G (TDK) and R8 47K. Indeed, I have tested it with several mobiles and works properly.
I would like considerate Tx coil Wurth 760308101103, but after replacing the coil and changing R8 to 82K, it doesn't work. For some second it tries to init the procces but finally it marks fault. I have tried disconnect SPR, SPL, FOD_E and FOD_T, but no results. Is any additional change necessary? Is Wurth 760308101103 compatible for charging standard mobiles?
The schematic is the same than application note one.
Thanks in advance.
Unbelievable! If the receiver and transmiter coils are separated around 3-5mm, it works perfect! The only explanation that I can find is that when coils are without separation the communication is not possible due to saturation of signal. I suppose that the shape of the ferrite Wurth 760308101103 concentrates the magnetic flux too much. Do you agree?
I have checked the values of R8/R9 (82K/47K) and I have even tried more permissive configuration like 100K/100K and finally no results, it tries to connect for some seconds (comsuption around 50-100mA) and after that it enters in fault state.
R13/R14 = 1.8K/27K are supposed OK.
the main difference is the DC resistance, 60mOhm vs 150mOhms