Multiple Coil with mux

Hi Sunny,

I would like to mux twelve PCB coils to one LDC1000. The coils would be about 1cm apart on a 3x4 grid. This means the coils farther from the LDC1000 will have longer mux-to-coil PCB trace length.

1) Would you recommend placing one tank capacitor between the mux and LDC1000, or tank cap for each coil? I anticipate using the same coil geometry for all, by the way.

2) Can you please provide a rough guideline for allowable parasitic L and C between the LDC1000 and coil, perhaps as a percent of coil inductance and tank capacitance? This will help me optimize layout and choose a mux.

Thanks!

Related to my muxing questions:

3) Would you recommend using two mux switches per coil, one for INA and INB?

The alternative would be making all the coil INB's common and the mux would select which coil connects to INA. But at high frequencies I'd imagine these "stubs" (unused coils) on INB could cause problems.

Thanks again

Hi,

1, It`s better place tank cap for each coils, that`s good for Q. 

2, There is no exact guideline on it, especially for different coils,  you can increase the inductance of the coil, that may help.

Hi, 

Yes, it`s better to use two mux per coil.

Regards, Sunny.