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Original question:

WEBENCH® Tools/LDC1612: LDC1612

LDC1612: Coil Sensor Manufacturing requirements & Vosc Set logic

Dinesh Kumar2
Prodigy 120 points
Part Number: LDC1612
Other Parts Discussed in Thread: , LDCCOILEVM

I designed a coil Sensor using Coil designer Webench tool. 14mm OD, 24 turns, 2 layer, 4mils Trace width & 4 mils trace spacing, Cap is 330pF. I evaluate this Coil Sensor with the help of LDC1612EVM kit to detect the IDrive required as I don't know the Rp of the sensor. Am Using LPCMCU (I2C) to communicate with the LDC1612 IC. Do I require separate logic to write in the MCU to alter the optimal Oscillation Voltage given to the coil sensor? Because even after changing the drive current, the Vosc remains same while connected with MCU, but it changes while it is connected with EVM.

Kindly suggest the method/parameters to uniformly manufacture the Coil sensor PCB to use it in my application, or please share the gerber file for the same (Found in LDC Reference Coil User Guide - Sensor coil "M"). As of now I need to check and set the drive current for each and every coil sensors to use in the module.

Expecting your valuable inputs.

Regards,

Dinesh

  • 0
    TI__Genius 17440 points

    Hello Dinesh,

    Changing the IDRIVE settings should change the sensor oscillation amplitude regardless of which MCU is communicating with the LDC1612. Please note that we do recommend configuring the LDC1612 while it is in sleep mode. What is the Vosc that you are measuring when you do not use the LDC1612EVM?

    You can find the gerber files for the LDCCOILEVM on the EVM product page: http://www.ti.com/tool/LDCCOILEVM

    Best Regards,

  • 0 in reply to Kristin Jones93
    TI__Genius 17440 points

    Hello,

    I haven't heard from you in a while, so I'm assuming you were able to resolve your issue. If this is not the case please feel free to reply to this thread or post a new question.

    Best Regards,

  • 0 in reply to Kristin Jones93
    Prodigy 120 points

    Hello Kristin,

    My issue hasn't resolved yet. The Vosc is around 1.4V when am not using the LDC1612EVM. 

    Coming to the gerber, I need some reliable method to validate the coil sensor PCBs before integrating it with my application. Please suggest if you have any tool/method to qualify the manufactured Coil sensor (as PCB) rather than the conventional method (using evaluation module. as it is not feasible for us)

    Eventhough the coil sensor PCBs are uniformly manufactured, we found that some sensors require drive current code 18 and some requires 26. Still we are not clear what manufacturing parameter in coil Sensor PCB making this difference.

    Please help to sort this out.

    Thanks & regards,

    Dinesh

  • 0 in reply to Dinesh Kumar2
    TI__Genius 17440 points

    Hello Dinesh,

    The best way to determine the drive current needed for your coil and to verify that your coils were manufactured correctly is to measure the Rp value. You can do this with one of the methods in this application note. I recommend the network analyzer or impedance analyzer if possible. 

    Is there a difference in the setup of your coils? For example, are they connected to the LDC1612 using cables of different lengths? If not, I suggest double-checking the capacitor values on the sensors and the sensor layout. A difference in drive current that significant is not normal for typical manufacturing tolerances; you shouldn't need to use different drive currents at all for identical coils.

    Best Regards,