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LDC1614-Q1: Design spiral coil sensor

Shinji Tsuji
Genius 13409 points
Part Number: LDC1614-Q1
Other Parts Discussed in Thread: LDC1614

Hi team,

I have a question about how to design a spiral inductor sensor for LDC1614.

The sensor is located >150mm away from LDC1614 input through PCB trace in my design.

Q1 : Is there a guideline of how to route the PCB trace? For example, don't bent 90degree, round shape the corner...

Q2 : I use Spiral_Inductor_Designer excel spread sheet.

I would plan to use the material called AZ91D for the target metal.

https://www.dynacast.jp/az91d

Is there a parameter I should change in the excel spread sheet for Rp calculation with target?

Q3 : When given the Rp is too small for LDC1614 to drive due to limited physical condition, is there any way to increase Rp?

regards, 

regards,

  • 0
    TI__Genius 17440 points

    Hello Tsuji-san,

    1. The INxA/INxB signals should be routed like differential pairs. Section 10 of the datasheet discusses layout further. As you can see in the example layout, we used 45 degree corners.

    2. The Spiral Inductor Designer only provides estimates for aluminum targets. However, you can use the Excel FEMM tool to experiment with different target responses. This tool uses the same Spiral Inductor Designer as an input and is included with the LDC Tools download. AZ91D may not be available in the list of possible target materials, but if you select a target material with similar conductivity then you will have a good approximation of the inductive response to the target.

    3. There are two main ways to increase Rp: increase L or decrease C. This is because Rp = Rs*L/C. You can make some improvements to Rp by minimizing Rs, but often changing L or C is easier. If you have a four-layer coil, you can reduce Rs using the method in section 2.3.2 of LDC Sensor Design. Otherwise, it's generally easiest to reduce the capacitance value.

    Best Regards,