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LDC1614EVM: Rp

Janine Lin
Expert 2190 points
Part Number: LDC1614EVM
Other Parts Discussed in Thread: LDC1614

Dear TI

I have some confusions about the parameters.  Here are my questions.

1. In the application note "Configuring Inductive to Digital Converters for parallel resistance (Rp), it says the current Idrive is depends 

on the value of Rp. Does this setting is for parallel coil, same as the figure below? 

2. What about if the design of the coil is in series connection, see figure below. What would be its current Idrive code?

 

Thank you.

Best Regards

Janine Lin

  • 0
    TI__Mastermind 23810 points
    Janine,

    The final Rp of the sensor is what matters when setting the IDRIVE current. Please note that you can easily set IDRIVE by using an oscilloscope once you have the sensor. This app note discusses how to do that:

    www.ti.com/.../snoa950
  • 0
    TI__Genius 17440 points

    Hi Janine,

    The current drive settings in Table 1 correspond to those specific Rp values, regardless of the coil design. You could have two very differently designed coils that have the same Rp value, and they would use the same current drive setting.

    If all of the coil parameters are the same except for whether the layers are connected in parallel or in series, the coil with the layers connected in parallel will have a higher Rp value (because it reduces the series resistance). Note that in either case you would still need to measure the Rp value using one of the methods in this application note and then use Table 1 to set the drive current appropriately. 

    Best Regards,

  • 0 in reply to Kristin Jones93
    Expert 2190 points
    Dear Clancy and Kristin


    I used a LDC1614 Coil Calculator to design a PCB coil. I want to ask, what is this Rp for? Is this the Rp value as for reference to see which Current Idrive code to be used?
  • 0 in reply to Janine Lin
    TI__Mastermind 23810 points
    Janine,

    That is exactly what it is for (and to make sure that you are in the allowed Rp range of the device). Rp given by the calculator is an estimate, so you may need to adjust the IDRIVE setting once you manufacture a prototype sensor.