TPS54240: coupled inductor

Dimitri Petrucci

Part Number: TPS54240

Hello

I got this PSU design around the TPS54240, basically it is the same design shown on the app.note SLVA369A (http://www.ti.com/lit/an/slva369a/slva369a.pdf), that uses this DC converter to get positive and negative outputs.

I need to select a different coupled inductor. At this time it is using a custom (not commercially available) coupled inductor with these specs:

I'd like to use a commercial inductor (available on Mouser or similar). Can anyone help me identify a similar part that would match the performances, or at least come close?

I'm a computer engineer, not an electrical engineer, so the best I could do is select those possible inductors, but I'm totally not sure about how they would perform. I simply choose a coupled 22uH inductor since the original one is 21uH/25uH.

1) https://www.vishay.com/docs/34359/ihcl-4040dz-5a22.pdf

2) http://www.mouser.it/Search/m_ProductDetail.aspx?Coilcraft%2fMSD1260-223MLB%2f&qs=zCSbvcPd3pa32vh7IhFCEQ==

Also I have the following questions:

- would this PSU design work if only the negative output is actually used, and not the positive?

- what is the positive and negative voltages before the two LDO regulators?

over 7 years ago

0 Ambreesh Tripathi over 7 years ago

TI__Expert 6860 points

Hi Dimitri ,

What is the current requirement on each output .

The vishay inductor closely resembles the cusotmized inductor .

---Ambreesh

0 Dimitri Petrucci over 7 years ago in reply to Ambreesh Tripathi

Prodigy 90 points

Thanks for the reply.
Actually I'm not aware of the requirements and about the specs of the PSU, I just know that I need to replace that inductor with minor changes in the performances. If the inductor is different, what spec could change in the performances? Less output mA?

0 Ambreesh Tripathi over 7 years ago in reply to Dimitri Petrucci

TI__Expert 6860 points

Hi Dmitiri ,

The AC , DC losses on these inductor could be different and hence efficiency can change . The Switch node ringing performance can also change because of different leakage inductance . If the Turns ratio are different than output voltage can change though in your case you are using LDO at the output which should regulate .\

---Ambreesh

0 Dimitri Petrucci over 7 years ago in reply to Ambreesh Tripathi

Prodigy 90 points

Thank you
Is there a design of this type on the webench? I'd like to simulate that.
Also, to understand what is the voltage and the current capability before the two LDOs on both rails (using a coupled 22uH inductor)

0 Ambreesh Tripathi over 7 years ago in reply to Dimitri Petrucci

TI__Expert 6860 points

Dimitri ,

You can use TPS54240 Pspice model (available in Tools and software section of product folder) for simulation .
Further please go over the app note below to get more info on bipolar supply design .
www.ti.com/.../slva369a.pdf

---Ambreesh

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TPS54240: coupled inductor