Part specs range for DCC inductors in nRF52840 QIAA var5 reference design

[joste]

I've implemented the nRF52840 QIAA var5 reference design in hardware and it works well. For L2 (10uH) and L3 (15nH), in series off the DCC pin B3, could you perhaps recommend a spec range for these parts so that I can have some flexibility with alternates, e.g. tolerance, DCR, anything else critical? Note I'm using 0603 and 0402 footprints respectively, and I'm particularly interested in L2. It's a very compact layout.

Any help appreciated, thanks.

[Simonr]

Hi

The main limitation is inductance and tolerance for these components. The DCR will affect the efficiency of the DCDC converter, and at a couple ohms might even inhibit operation, so you would want to keep it as low as possible. The required specs of these components can be found in the BOM for the circuit configurations using the DCDC components on the Infocenter. 

The 15nH inductor should be a high-frequency inductor. We suggest that both inductors are used for optimal operation when using the DCDC, and the reason is that big 10uH inductors behave differently than small 15nH inductors. The 10uH inductor is bad at filtering out the higher frequencies. We have added a smaller one to take care of these.

Best regards,

Simon