Minimum inductor value for DCDC converter?

[Jaison]

Hi,

We are trying to have a thin beacon design. But we are having difficulty in finding low profile inductor for dc-dc converter matching the recommended value of 10uH. What would be the minimum possible value at which the dc-dc can reliably operate? What would be the negative effects of reducing inductance?.

Chip: nRF52832 sdk: nRF_sdk_13 SoftdDevice: S132-SD-v4

Thanks and regards Jaison

[Sigurd]

Hi,

It might work with a slightly lower value, but it is not something we recommend and it will be outside the specification of the chip and can make the DCDC converter unstable.

A solution can be to use several smaller low-profile inductors in series, making it ~10 µH in total. E.g. you can use 3 low-profile 3.3µH in series to obtain the correct inductance.

[Sigurd]

If you cannot ensure that the total inductance is ~10 uH in the DCDC feedback loop, I would have to recommend that LDO mode is used.

[Jaison]

Thanks for your confirmation.

[AmbystomaLabs]

I just thought I would point out that the nominal height of an 0603 inductor (ie, the 10uH) is 0.8mm whereas the nominal height of the nRF52832 is 0.85mm.

So, there is no savings in profile height by going with a smaller package inductor.

[Sigurd]

Could be that he's using WLCSP packet where the height is ~0.375 mm

[AmbystomaLabs]

Good point.