LDC1614: Question for the inductive sensing

Hello,
Thanks for your interest in the LDC1614. Would you mind sharing what the intended application is?
With regards to your questions, let me answer them below.

user4271222 said:

1.
LDC1614 can make L-C tank oscillate.
How does LDC1614 make L-C tank oscillate and keep resonation?

The LDC1614 drives the LC sensor and maintains the oscillation as part of the normal operation. You can find more information on the basics of inductive sensing from our application notes page;

http://www.ti.com/lsds/ti/sensing-products/inductive-sensing/inductive-sensing-technical-documents.page?familyId=3244&docCategoryId=1

I recommend that you start with the LDC Device Selection Guide [SNOA954]

user4271222 said:

2.
How to select proper CHx_SETTLECOUNT?
How to take proper margin for CHx_SETTLECOUNT?

Settle count is used at the beginning of the oscillation measurement to ensure that the oscillation is stable before it begins taking measurements. Depending on the Q factor of the LC sensor, it may take the oscillation longer to reach the stable oscillation so you should increase the settle count to allow for this to occur. Refer to figures 12 and 13 of the LDC1614 datasheet. Typically the easiest way to determine the best value is to probe the sensor on an oscilloscope and measure the length of time it takes to reach a steady amplitude and calculate the appropriate CHX_SETTLECOUNT value from equation 3 of the LDC1614 datasheet.

user4271222 said:

3.
What is the purpose of CHx_RCOUNT register setting?
What is the criteria to select RCOUNT?

RCOUNT is used to set the conversion time of the measurement. It also has an impact on the resolution of the data. Please refer to the following app note for more information: Optimizing L Measurement Resolution for the LDC161x and LDC1101 [SNOA944]

user4271222 said:

4.
Regarding to (CHx_RCOUNT * 16) /Fref, the minimum conversion time
would be offered as 5*16 /Fref = 80/Fref.
Does it mean the reference clock should count 80 times at least for conversion?

This calculation is referring to the wait time before the measurement begins.

user4271222 said:

5.
What timing is the conversion result (data) updated in DATA register?

The calculation for conversion time is provided in equation 6 of the LDC1614 datasheet. Note that the time it takes for a measurement to be complete is broken into 3 parts: sensor activation time + conversion time + channel switch delay. Channel switch delay can be calculated from equation 7.

user4271222 said:

6.
The explanation of offset in the datasheet says the offset value can lead to maximize the dynamic range of teh sample data. Why can the offset value maximize the dynamic range?
When the OFFSET is 0x0, it offers maximum dynamic range, doesn't it?

The OFFSET feature is primarily useful for the LDC1314 and LDC1312 devices. You can find more information on this feature in the following blog post: e2e.ti.com/.../inductive-sensing-improve-the-enob-of-a-multichannel-ldc-by-4-bits-in-3-simple-steps

Best regards,
Luke LaPointe