LDC1101: custom coil of same inductance produces too high frequency

Olaf Albert

Hi TI team,

I tried to manufacture my own coils with CuL wires in ferrite pot core halfs (high frequency EPCOS K1 material) to optimize the sensing distance and replace the EVM coil with it. I tried several shapes and winding constructions but always experience a much higher frequency (e.g. 10,8MHz) and damping(?). The inductance is quite the same (7,2µH vs. 7,4µH) and also a sweep with an generator and an fft capable scope show similar curves. The DC resistant far below 1 Ohm.

What can be the problem? Or which register/parameter setting do you suggest I should change in the GUI?

scope screen shot of the own coil signals (differential -> F4)

Thank you for your help!

Best regards,

Olaf

over 9 years ago

0 Chris Oberhauser66 over 9 years ago

TI__Genius 14270 points

Hello Olaf,

It is possible that the low frequency inductance is the same, but at the higher frequencies the LDC operates at, the ferrite maximum flux density of the ferrite decreases; which results in a lower than expected inductance at the operating frequency.

Regards,

ChrisO

0 Olaf Albert over 9 years ago in reply to Chris Oberhauser66

Intellectual 320 points

Hello Chris,

Thank you for your answer!

Meanwhile I conducted some measurements (frequency sweeps) with large signals (to monitor nonlinearities) and figured out, that my resonator capacitor was broken.

Sometimes engineering is soo simple... ;-)

Best regards,

Olaf

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LDC1101: custom coil of same inductance produces too high frequency