I wanted to solve this problem by myself, but I need somebody to help me.
I'm really really trying to find way to calculate it, but I cant.
In the LDC1614 datasheet, There is one example.
L = 43.9u
C = 100p
and Resonant Frequency = 2.4M
Then
Rp = 6.6K
So I try to calculate it myself.
Rp = L/(Rs*C)
So,
Rs = 2 * 3.14 * 2.4M * 43.9u = 661.66 ohm
Rp = 43.9u / ( 661.66 * 100p) = 663.48 ohm
Why My Rp value is 663.48 ohm but in Datasheet is 6.6 Kohm?
I cnat understand.
Could somebody help me please? I'm struggling with this for a week.......
Best Regards
p.s :
I found this documant.
Maybe only to know Rp is Measure directly.
So I determine to measure it with function generator.
ps2 :
I found this documantation.
Q23: How can I determine the optimal drive current on LDC1312, LDC1314, LDC1612, or LDC1614 if I don't know RP?
Answer: For best performance, the following procedure is recommended for each channel:
One-time system calibration:
1.Move the target to the maximum distance from the sensor
2.Set SETTLECOUNT_CHx.CHx_SETTLECOUNT according to the reference clock, sensor frequency, and sensor Q factor
3.Enable auto-calibration by setting CONFIG.RP_OVERRIDE_EN to b0
4.Set CONFIG.SLEEP_MODE_EN to b0
5.Wait until the device has performed at least one conversion for each channel
6.Copy the value of DRIVE_CURRENT_CHx.CHx_INIT_IDRIVE into non-volatile memory
Upon power-up:
1.For each channel, copy the value of the previously recorded CHx_INIT_IDRIVE setting into register DRIVE_CURRENT_CHx.CHx_IDRIVE
2.Disable auto-calibration by setting CONFIG.RP_OVERRIDE_EN to 1
3.Disable auto-amplitude correction by setting CONFIG.AUTO_AMP_DIS to 1
Q is ,
connect an oscilloscope probe on INAx to ground. For example, if you turn on the sensor it might take 15 cycles of the sensor frequency for the sensor amplitude to reach the constant amplitude; so you would use Q=15 in the equation.
please check it.
https://e2e.ti.com/support/sensor/inductive-sensing/f/938/p/475428/1710567#1710567
I hope it is help for sombody.
Best Regards.
