Reasons of differences between tida-00334 and tida-00415 (and tida-00623)

Frederic,

The limitations on the different TIDA designs you've investigated, it's the practical power that can be transferred by their respective coils.

The question you have to answer is which coil size meets your needs?  That is really for both the TX and RX.  

Once you determine the coil size and application size that works best in your application, that my help choose the path for you.  The cost of the overall BOM can be a consideration as well.

Regards,

Dick

Hi,

Thank you for your answer.

So it's relly the coil caracteristics which limit the power.
I guess differents design it's a kind of optimization evolution over the elapsed time.

I would like to use this Wurth coil : katalog.we-online.de/.../760308101220.pdf
It's small but It's rated at 1.1A, so it should be ok for 2.5W?

thank you

edit: About the current value to set, I guess it's set by the receiver part and not the transmitter part.

Frederic,

The inductance of the TX coil must be tied to the solution.
For the full-bridge TIDA-00334, the coil inductance should be 6.3uH.
For the half-bridge TIDA-00415, the coil inductance should be 3.3uH.

Note that the DCR of the coil must be low due to the circulating current. Your coil selection shows 0.28 ohms while the 334/415 resistances are 0.15/0.6 ohms respectively.

Regards,

Dick

Hi,

Sorry, I made a mistake, this coil is for the RX part.

For the TX part, I though about those 2 :

The dcr and inductance seem to be what you said.

frederic

Hi,

I think I will use the tida-00623.

But I can't find coil with the fit inductance.

What have i to change to change the inductance output for using an other coil?

I can't find how the inductance is set.

thank you

Hi,

I can't find where to set the inductance coil.

So I will get a coil that fit with requirement but it's bigger than the RX coil.

I saw that size coils should be almost the same for better performance.

So, with a TX coil of 43mm and a RX coil of 17mm, is it ok or is there too much difference?

thank you

Frederic,

Your are correct that the size ratio between the RX and TX is important.  The coupling decreases as the RX:TX ration gets smaller. 

The coil used on the TIDA-00762 is 760308101103 from Wurth Electronik.  It is 6.5uH and 30mm in diameter.  

A 43mm coil can work with an RX coil of 17mm, but coupling will be difficult.  I have quite successfully worked with a 43mm TX and a 20mm RX.  See the TIDA-00318 reference design for an example.

Regards,

Dick

Hi,

Thank you for the link, there is a lot of informations.

I think I can finish my design now.

thank you