LDC1101: Coil and assembly design questions

Supira Medical

Part Number: LDC1101

Tool/software:

Hi,

I have a space-constrained application where the coil assembly must fit within a 6 mm diameter cylindrical hole. If I use a 4-layer PCB coil, there isn't room for the tank capacitor in-plane. Is it acceptable to mount the capacitor slightly away from the coil, in say a perpendicular orientation? I assume that it isn't a good idea to place the capacitor in the center of the coil?

Are there any recommended wire-wound inductors that meet the crisscrossed winding requirement? I have flexibility in the air gap dimension. Can I house the sensor assembly in a metal tube without degrading the performance of the system?

Thanks!

over 1 year ago

0 Eddie LaCost over 1 year ago

TI__Mastermind 44745 points

Hello,

Yes, the capacitor could be placed a short distance from the coil, but you want to keep it as close as possible. In our coil example EVM kit, we have 4mm, 5mm, and 6mm example coils that you could reference. These are coils "P, Q, and R" in the document.

https://www.ti.com/lit/ug/snou136/snou136.pdf

In the post below, you can also find details about using a wirewound surface mount inductor as a sensor, which could be useful in your application.

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1377235/ldc0851-where-is-the-blog-post-how-to-use-a-tiny-2mm-pcb-inductor-as-a-sensor

It depends on the spacing the sensor will have from the metal and what air gap is required. It is likely that the metal surrounding would dampen the coil, but the performance may still be acceptable for your use case.

0 Supira Medical over 1 year ago in reply to Eddie LaCost

Intellectual 300 points

Hi Eddie,

Thanks for the reply; yes, I had seen these two topics earlier. In the latter, the discussion is around adding a series inductor to the one on the PCB. I was hoping it was possible to use just a wire wound inductor with no PCB coil. One could 3D print a small bobbin that also houses the capacitor.

Thanks!

0 Eddie LaCost over 1 year ago in reply to Supira Medical

TI__Mastermind 44745 points

Supira,

You can also use unshielded inductors as the sensing coil. Keep in mind that small surface mount inductors will have a very short sensing range. As you mentioned, a 3d print bobbin with wire wound could work as well.

0 Supira Medical over 1 year ago in reply to Eddie LaCost

Intellectual 300 points

Thanks, Eddie.

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LDC1101: Coil and assembly design questions