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How to determine Rp for LDC1614

JAy
Prodigy 80 points
Other Parts Discussed in Thread: LDC1614

Hi .

I'm following 8.2.2 Detailed Design Procedure instruction of LDC1614 Datasheet.

Example coil preperence is 

Rp = 6.6 kΩ, L = 43.9 µH, C = 100 pF.

In the senction 2, There is mention about Q.

(a) CH0_SETTLECOUNT ≥ Q × f REF0 / (16 × f SENSOR0 )

SO I try to determine Q.

But, How to determine Rp for my custom coil?

WEBBENCH can design only for PCB Coil. But I wanna design for solenoid.

How to calculate Rp by L,C? 

Have a good day.

 

  • 0
    TI__Genius 14270 points
    Hi Jay,

    It looks like you want to set the SETTLECOUNT but do not know your Q or Rp. There is an easy way to get around that. You can determine the appropriate setting to use for the SETTLECOUNT registers using an oscilloscope - first make sure SENSOR_ACTIVATE_SEL is set to Low Power Activation mode. Then set the channel SETTLECOUNT to a high value (such as 0x8000). Setup the other register settings as appropriate, and put the device into active mode.

    Probe INAx to ground, and capture the turn-on signal. Measure the amount of time it takes for the sensor amplitude to stabilize to within 1% of its final amplitude. Then:

    SETTLECOUNT = fref * measured_time / 16


    Regards,

    ChrisO
  • 0 in reply to Chris Oberhauser66
    Prodigy 80 points
    Oh, Thank you very much.
    I have one question.
    INAx to GND is only way to check signal?
    INBx to GND or INAx to INBx is not possible?

    Best Regards.
  • 0 in reply to JAy
    TI__Genius 14270 points
    INAx to Gnd or INBx to Gnd will be the same signal, so you can check either signal.

    INAx to INBx is ok, as long as you are using a differential probe and not a ground lead (do not ground either INAx or INBx).

    Regards,

    Chris O