1
\$\begingroup\$

While learning and trying to make my first two-phase buck converter to power some servos, I found 2 x 3.3 uH inductors are needed for an application that will draw 30A (15A each). The problem is that the switching buck converter IC LM5143A-Q1(link to datasheet) has a max output current of 40A, so we're really close to its max specs. So, what MAX current should I pick for the inductor's rating? I found ones that go as high as 30A MAX DC current. In theory, we only need 15A for each, but isn't it safe to go a bit higher? But then again, if we pick the 30A, then won't that allow the inductors to draw 30A each and literally burn the IC at 60A? If the application only draws 30A, it won't draw more than that, right? So it's safe to go with the higher rating ones?

I was also thinking going for a slightly higher current rating would lower the chances of heat going wild. The operating frequency it'll use is 100kHz

\$\endgroup\$
1
  • \$\begingroup\$ The 30-A limit you refer to is linked to the demo board, not the IC which drives two external MOSFETs. If you have 15 A dc in the inductor, the peak value will be half of the selected ripple above the dc. Also, something worth looking at is the inductance versus current curve for the type you've selected. Operating temperature also influences the inductor saturation limit. \$\endgroup\$ Jul 23, 2023 at 17:43

1 Answer 1

1
\$\begingroup\$

The current rating of the inductor won’t come into play until you hit the limit and the inductor saturates. Before that, the converter have no idea if you are using two 3.3 uH 30 A inductors or two 3.3 uH 60 A inductors.

Feel free to go higher in inductor current rating if you need lower DCR or optimal value isn’t available to you.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.