LDC1614: What is the inductive input range of LDC1614?

Boram,

The LDC1614 - indeed, all LDC devices - can be thought of as data converters, but not the same type of data converters as the familiar analog-to-digital converters (ADCs).

LDCs do not have the max & min limits like conventional ADCs have. LDCs function as LC-based oscillators where the L-value (and the device's LC oscillator frequency) varies as a conductive target moves closer to or away from the sense coil (which acts as an inductor).

If the conductive target does not move, the LDC will output a more-or-less constant data value.
If the target moves, the sensor's inductance changes, and subsequently the LDC's oscillator frequency changes, and the LDC output data changes.
The inductance is 

The inductance ranges are dependent on the min and max limits of the LDC1614 sensor's resonant frequency (1kHz - 10MHz)  and the Q (= Rp√C/L) of the sensor circuit.
If the L becomes too large, or the LC circuit's parallel resistance (Rp) is too small, the Q will be too small and the LDC oscillator will not work.

Sorry we can't give hard-and-fast limits you have asked for, but much of it depends on your implementation and your design parameters.

One approach worth trying is to download the Inductive Sensing Calculator Tool and experiment with sensor values in the Spiral_Inductor_Designer tab. 
The tool will let you know if the design parameters result in values outside of the LDC1614 operating range.
When the sensor values are solid, you can review recommended device register settings in the LDC131x-LDC161x_Config tab.

The app note LDC1612/LDC1614 Linear Position Sensing gives some design guidelines & examples using the LDC161x/131x devices in linear sensing applications.

If you would like to know more about inductive position sensing, please see our E2E Inductive sensing FAQ page.

Regards,
John