LDC3114: Reference coil design

Hello, 

?? ?? said:

For our reference, first we set parametor that TI team designed for themseves.

I believe you are referring to the design shared with Toshiro. Here is the FPCB that we were discussing: 

1. Sensor Capacitance
   1. This value can be set to adjust the sensor resonant frequency if needed. In the testing previously shared, the BOOST-LDC3114EVM was used which has a 220pF capacitor for this value. 
2. Outer diameter of the inductor
   1. Since it is a racetrack style coil, there is a short size and long side for the diameter. The corresponding values are 15mm and 35mm. 
3. PCB Thickness
   1. The FPCB that this was built on has a thickness of 0.26mm 
4. Copper thickness
   1. For this, 1oz copper was used. 
5. Target distance 
   1. For the example previously shared, a target distance of about 0.4mm was used. 

With all of this, the Spiral Inductor Designer tab of the LDC_Tools-ext51.xlsx spreadsheet should look like this: 

Best Regards, 
Justin Beigel

Hello Justin-san

Thank you for information of your FPC design.
It is very helpful for our design, we proceed our own FPC design.

Best regards,
Hirohisa

Hello Hirohisa-san, 

Here are the top and bottom layers of the FPCB respectively: 

The main concern for the layout is to follow the coil winding recommendations from section 2.3 of our Sensor Design for Inductive Sensing Applications Using LDC (Rev. C) app note: 

Best Regards, 

Justin Beigel

Hello, Justine-san

Thank you for providing bottom layer pattern image.
I understanad precautions that pattern layout on multilayer boards, such as placing them in the opposite direction.
I check carefully application note.

Best regards,
Hirohisa

Hello Hirohisa-san, 

For this application, you are utilizing the bend in the sensor to create the dynamic range in your data. To maximize the dynamic range of the data, I think it is then best to use a racetrack style coil and ensure the long side of the inductor is a larger value to allow for more coil area to change as the bend occurs. It would be important to keep in mind the physical space you have available for the sensor implementation for this. Smaller trace widths and spacing can be used if you need to add more turns to increase the inductance of the coil. Alternatively, larger trace widths can increase the parallel resistance of the coil which helps reduce the current consumption of the coil while it is active. 

Hope this helps. 

Best Regards,
Justin Beigel

Hello Hirohisa-san, 

Happy to help. I am going to mark this thread as closed for now but feel free to ask follow up questions here or in a new thread if you need. 

Best Regards, 
Justin Beigel