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Inductor Considerations for NRF 52832 DC/DC Converter

edougal

Hey, I was considering designing a piece of hardware using the NRF52832 and I want to use the DC/DC converter to save battery life. There are no considerations for choosing an inductor in the LC filter given in the NRF52832 product specification. Why are two inductors used in series in the NRF development board (L2 is 10uH and L3 is 15nH)? Can only L2 be used?

Thanks.

  • 0

    Hi,

    The 10 uH is the main inductor for the DCDC buck regulator, and the smaller 15 nH is present to filter the signal. Both are required for optimal operation when using the DCDC.

    If you open the nrf52832_qfaa_dcdc_schematic.pdf from our reference design .zip file, and click on the components, you will get a more detailed view of the components, with links to the datasheet etc:

    image description

    Cheers, Håkon

  • 0

    I also think about using just one inductor - it can be ferrite, with approx 10 uH inductance and good Q at 8MHz of switching and losses rising well above that it should be OK. I'm not sure about performance at 2.4 GHz (any switching noise leaking may affect the receiver performance), as ferrites datasheets only sometimes extend beyond 1GHz. Regards Tomasz

  • 0

    What about using multilayer type instead of wirewound for the main 10 uH inductor? It can handle enough current, has low DCR and high SFR. Am I missing something?

  • 0

    How will not mounting the 15 nH inductor affect the sensitivity? And does using the DCDC, with recommended components, affect the sensitivity in any way?

  • 0 in reply to FredrikK

    How ignoring the inductor reduces sensitivity? My guess: 15nH has decent inductive reactance (over 200R) only at 2.45 GHz and above. It means it's placed for a reason - to reduce switching noise floor and help to receive weak signals. 10uH main inductor will become capacitive just beyond 10MHz!¬ I didn't find any ferrite offering me 10uH predictable inductance and low losses at 8MHz. 2 components are needed. On the other hand: many data lines ferrites may do much better filtering job than 15nH inductor.

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