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Recommended inductor for Y-TRAP of AD725

Inductor devices do have more properties than just an inductance.

Datasheet, evaluation board document and other resources I find on the internet do not give any idea other than 68 uH inductance. Here's a pic of possibly well performing inductor:

The one almost at the center marked 680J is expected to be the required inductor, its length must be 2.1 mm (comparing to the size of AD725), but I can not find such inductors.

I would appreciate if AD people would give part numbers of recommended (or successfully used) inductors, and then I will find out my way to source appropriate one locally.

Thank you.

Update: (after Guenter's reply)

The board in the picture above is Altium "12-404-PB01 -  Audio/Video Peripheral Board, Provides a Stereo Audio CODEC, 24-Bit VGA Output", here's the circuit diagram


The document does not list the BOM, but each component has more or less complete characteristic written on. For Y-trap inductor it has "68uH 80mA 5.5R" title, thus it is very close to the Guenter's proposed part.

Update: here's the final product based on the AD725.

added final product image
[edited by: Eugeny Brychkov at 9:59 PM (GMT 0) on 12 Nov 2019]
[edited by: Eugeny Brychkov at 9:59 PM (GMT 0) on 12 Nov 2019]
Parents Reply
  • Hello Guenter, thank you very much for the information, very appreciated.

    I originally have chosen VLS5045EX-680M, but now I have decided that it is an overkill in terms of size and power rating. Looking into BOM file I see B82464G4683M, which is an even bigger in size - and is comparable to the size of the AD725 - but has much less DC resistance. Looking into the evaluation board sketch I do not see such big device on the board, and there must be a mistake in the BOM. Please confirm.

    The datasheet for B82422A1683K100 you attached seems (to me) to be of an appropriate size (picture dimension in my original post must be approx. L=3.2 mm), is rated 80 mA and having DC resistance of 7.7 Ohms (the high resistance may be a major cause of the losses during operation). Is this the one actually installed on the board? It's a great pity that I can not find photo of the evaluation board in the internet...

  • Unfortunately I don't know which board the picture comes from .  The only AD725 eval board I found was the one I attached.  Are there any other numbers on the board you are looking at?

    This chip and eval board is 20+ years old and the people who did it are gone or have forgotten all about it.  I need the numbers on the board to track further

    As far as the trap inductor, power/current is not important.  What is important is part value and DCR.  Of course the value must be accurate and DCR relatively low so it doesn't affect the filter loop calculations

  • Guenter, apologies - can you advise as a SME - if DCR of 5.5 Ohms (for part installed on this Altium board) or 7.7 Ohms (declared for B82422A1683K100) acceptable in this circuit, or should we strive for 130 mOhms (thus use big power inductor)?

    I am questioning so much about it because I have made proto board using AD725, and it appeared that Y-trap did more harm to the composite image than good. My belief that I have chosen wrong parts, or did wrong layout (it was made using P2P wiring - you can see the photo of it here, including the inductor I have chosen).

  • The B82422.... should work fine.  5.5 vs 7.7 Ohm is not any real difference in the circuit.  

    Looking at the link for the board/schematic explains a lot.  Video and fly wires together make me cringe.  Never a good plan.

  • Guenter, great, thank you for the assessment (I have simulated it in LTspice to find out no much difference too). I agree with you, that was a quick proto showing that chip works, but I had a lot of problems during making it up and running more or less properly. I am working on the PCB implemeting experience gained and expecting it to have proper layout and performing well.

    I must say that image AD725 produces is superior - that's why I keep fighting having it in.

    Again thank you very much for your support.