LDC1000 LC Tank loading

Matthew Webster

Hello,

I am wanting to use the LDC1000 in an application that reqires a redundant capaciative burrier between the LDC1000 output driver (LC TANK) and probe.

I experimented by adding two 0.01uF series caps to one lead of my external the probe and was not abel to ready any results.

What is the maximum load capacatance that the INA/B driver can handle?

Regards,

Matthew

over 10 years ago

0 Chris Oberhauser66 over 10 years ago

TI__Genius 14270 points

Hello Matt,

Please make sure the impedance of the series capacitors is not too large, as the self resonant frequency may be too low for the sensor resonant frequency.

Regards,

ChrisO

0 Matthew Webster over 10 years ago in reply to Chris Oberhauser66

Prodigy 50 points

Chris,

What would be considered too large of capacitance?

0 Chris Oberhauser66 over 10 years ago in reply to Matthew Webster

TI__Genius 14270 points

Hi Matt,

The maximum capacitance depends on the parasitic resistance and the inductance of the inductor. As the capacitor gets larger, the sensor frequency decreases, and the RP of the sensor decreases. When the sensor RP is too low (for the LDC1000, this is at 1kohm), the LDC can no longer maintain the sensor amplitude.

If you know the AC resistance of the inductor at the operating frequency, you can use the calculator on the front page of the LDC tools calculator spreadsheet (at www.ti.com/.../slyc137) to find the maximum capacitance (and the lowest compliant sensor frequency).

Regards,

ChrisO

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LDC1000 LC Tank loading