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LDC1612 / to determine the optimal drive current

K.Yaita
Guru 29720 points
Other Parts Discussed in Thread: LDC1314, LDC1312, LDC1612, LDC1614

Hi Team,

I found the information "How can I determine the optimal drive current on LDC1312, LDC1314, LDC1612, or LDC1614 if I don't know RP?" as the following.
https://e2e.ti.com/support/sensor/inductive-sensing/f/938/t/295036#Q23
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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
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How to estimate "sensor Q factor" although don't know RP?

Best Regards,
Yaita / Japan disty

  • 0
    TI__Genius 14270 points
    Hello Yaita,

    You can estimate the sensor Q by counting the number of cycles it takes for the sensor amplitude to stabilize. So, 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.

    I recommend having the SENSOR_ACTIVATE_SEL = low power activation mode (1) when you make this measurement.

    Regards,

    Chris O
  • 0 in reply to Chris Oberhauser66
    Guru 29720 points

    Hi Chris-san,

    Thank you for your advice.
    I understood.

    I believe I can also estimate sensor frequency without calculation to probe on INxA to ground.
    Is my understanding correct?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 14270 points

    Hello Yaiti-san,

    Yes, you can also measure the sensor frequency using the scope. Note that this frequency measurement will not be as accurate as the LDC1312 or LDC1612 can measure, but it should be sufficient to make a good estimate for to configure the LDC.

    Regards,

    ChrisO