DCDC Circuit configuration no. 1 for QFAA QFN48

[xusbzi]

Hello,

I am developing a board using the nRF52840 QFN48 and powering it using a 3.7V single cell LiPo battery. Since the battery voltage is stepped down to 3.3V via an external DC-DC converter (XCL210D331GR-G) and I plan on using the internal LDO on the nRF, do I still require L3 L4 C14 and C15? What about C11 or C12? I am trying to limit the size of my design as much as possible.

Any help would be greatly appreciated! Thanks!

-Paul

[JT898]

From the PS V1.11, page 938:

"Components required for DC/DC function are only needed if DC/DC mode is enabled for that regulator."

So no, L3, L4, C14 and C15 are not required if you are not enabling the DCDC in software (5.3.1.1) however I suggest you read through the Product Specs again to decide. Also you will still need to short DEC4 with DEC6. The DCDC way are usually more power efficient hence saving you some battery life running the nrf52. Note that your sync buck is at it's highest eff at Vin=3.6V, shouldn't you try your best to reduce power consumption on your overall circuit? ;)

C11 and C12 are a must for DEC3 and VDD decoupling.

Good luck!

[mathiaso]

Hi, Paul.

And thank you for your explanation, JT898.

What JT898 writes is mostly correct. Just keep C14 as well.

Graphic explanations of the different regulator configurations are found in the Regulator configuration examples section of the datasheet.

Best regards,
Mathias