• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 31 subscribers
  • Views 296 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

FDC2212: Electric components in the middle of the sensor coil

Daniel Murkrow
Prodigy 10 points
Part Number: FDC2212

Tool/software:

Hello,

we are currently developing a device, which emits light. To ensure that the light can't be directly emitted to the eyes, we wan't to use the FDC2212 to detect if something is covering the light source. To achieve that, the light source have to be placed in the middle of the sensor. 

For example like in the image below. The outer light green ring would be the sensor and connected from the back.

.

Here a some addition Information, if needed:

  • On top of the light/sensor comes a few millimeters of acrylic and a 5mm silicon pillow. 
  • A galvanic isolated power supply is used.
  • It has to withstand an medical grade EMI exam (80MHz - 2,7GHz @ 10V/m and 385MHz - 5,8Ghz @ 9V/m - 28 V/m )

1. Is a setup like this possible? Would it help to split the sensor areas into two rectangles?
The driver for the led has no fixed frequency, but a maximum switching frequency of 1MHz. There are already filters before the led and the current ripple is very small.

2. What is the preferred way to route the coil? In the image above I used a solid plane. Is there a benefit of using multiple small paths like in the image below?

3. Since the frequencies during the EMI immunity Exam are much higher, is the probability that the device is affected low? Or are there are points to consider (just regarding this sensor)?

Best Regards, 

Daniel

  • 0
    TI__Expert 7950 points

    Hi Daniel,

    Thank you for posting to the sensors forum. 

    Today is a holiday in the US and our team is out of office. We will do our best to provide a response by end of day July 5. 

    Best regards,

    Jesse

  • 0 in reply to Jesse Baker
    TI__Mastermind 18545 points

    Hello Daniel, 

    Daniel Murkrow said:
    1. Is a setup like this possible? Would it help to split the sensor areas into two rectangles?
    The driver for the led has no fixed frequency, but a maximum switching frequency of 1MHz. There are already filters before the led and the current ripple is very small.

    This setup is possible. It would be important to ensure that the LC tank frequency of the FDC2212 is separated from the max switching frequency of the LED to minimize any potential crosstalk. 

    Daniel Murkrow said:
    2. What is the preferred way to route the coil? In the image above I used a solid plane. Is there a benefit of using multiple small paths like in the image below?

    The image you shared here is how we route our inductive sensing coils that couple to a metal target. For a capacitive solution, you are better using a solid plane. 

    Daniel Murkrow said:
    3. Since the frequencies during the EMI immunity Exam are much higher, is the probability that the device is affected low? Or are there are points to consider (just regarding this sensor)?

    For the FDC2212, you can implement an EMI filter between the IC and the LC tank. You can follow the techniques in section 2.2 of the EMI Considerations for Inductive Sensing application note since the LC tank is a similar operation here. 

    Best Regards, 

    Justin Beigel