The Reason for Inductors on Pins DCC and DCCH

RE: The Reason for Inductors on Pins DCC and DCCH

Styve Naoue — Wed, 11 Nov 2020 13:56:27 GMT

Thanks once more.

RE: The Reason for Inductors on Pins DCC and DCCH

Andreas — Wed, 11 Nov 2020 13:31:20 GMT

Hi,

The 10µH is the inductor used by the DCDC regulator, the 15nH is a RF-choke to limit the amount of high-frequency noise injected to the internal supply. These two components have different frequency characteristics, so it is not possible to combine them to one unfortunately.

Correct, 8-12µH is fine, but if you use a part closer to the edge (e.g. an 8.2µH), the tolerance must be tighter so that even the units that are on the limit are inside.

Best regards,
Andreas

RE: The Reason for Inductors on Pins DCC and DCCH

Styve Naoue — Wed, 11 Nov 2020 12:09:25 GMT

Hello Andreas,

I have a follow up question about the inductors L2 and L3 in ref circuit no.4 for the nRF52840.

Why use 2 inductor for L2 = 10 µH Chip inductor, IDC,min = 50 mA, ±20 % and L3 = 15nH High frequency chip inductor ±10 % instead of just one inductor component of L=10.015uH ?

I believe with the given tolerance, inductivity between 8 to 12 uH is allowed right?

Thanks again for the reply in advance.

RE: The Reason for Inductors on Pins DCC and DCCH

Styve Naoue — Tue, 10 Nov 2020 14:41:25 GMT

Hello @Andreas,

Thanks for the quick reply. My question is answered.

RE: The Reason for Inductors on Pins DCC and DCCH

Andreas — Tue, 10 Nov 2020 14:32:43 GMT

Hi,

See the POWER section in the PS. The inductors need to be assembled in order to enable the on-board DCDC converter mode of the power supply. Pros of this is lower current consumption than the LDO mode it would otherwise be in, cons: external inductors. If you do not plan to use the DCDC mode, then leave the pins floating.

Best regards,
Andreas