What is the dv/dt side of an inductor

[Demon]

I just noticed that the XAL1010 inductor has a "recommended polarity".

9871


Would that be side A or B?

Couldn't find a meaningful description in google.


(please say B ... please say B ... please say B ... please say B ... )

[pedja089]

Sorry, A...

[pedja089]

On B side in ideal condition you have 0dv/dt. Because that is constant DC voltage smoothed by capacitor. in reality, you have some ripple...
On side A you have in one moment Vin, in next momement you have 0V. So there is source of your EMI. If you must choose right side of inductor, then you have much more problems in your design. Layout is 1000 times more important than side of inductor.
Just don't make terible PBC, and you don't have to worry about it... Especialy if your product is not going for certification...

[Demon]

...Just don't make terible PBC, and you don't have to worry about it... Especialy if your product is not going for certification...


I'm not going for certification. But I would have liked to put all the chances on my side for the lowest ripple this design can produce.

I assume CoilCraft didn't put that comment for nothing. I just have no idea if having it backwards costs me 1-2mV in the ripples, or 8-10mV.

I already have ideas for v3, so I'll be sure to have properly then.

[richard]

its about EMI not ripple

[Ioannis]

ripple would be the same in either direction.

As shielded inductor, this has to do with EMI only.

Do not worry.

Ioannis

[rsocor01]

I think it depends on the load at Vout. If Vin is a battery input there shouldn't be a large dV/dt on the battery side.

[Demon]

I think it depends on the load at Vout. If Vin is a battery input there shouldn't be a large dV/dt on the battery side.

It's a desktop USB application; never going to run on batteries.

The circuit is designed (by Texas Instruments) to handle wall adapters from 7V to 16V (datasheet for TPS56637 says it can handle up to 28V, but that wasn't my objective).

[Demon]

ripple would be the same in either direction.

As shielded inductor, this has to do with EMI only.

Do not worry.

Ioannis


Still, I'll reverse the pinout for the part in Kicad and add a comment; just to keep things clean.

I'd hate to use this part later and have EMI come and bite me in the asparagus.

[Ioannis]

Sure, do it if you can. Will not hurt. On the contrary.

The EMI will be less but i bet you won't be able to check the difference without proper tools (EMI antennas and Analyzers).

Ioannis