Are there switching regulators inside this RF chip? - Page 1
Forum section: electronics / rf-microwave

author: makebit
author_rank: Unknown
timestamp: September 29, 2025, 10:06:22 pm
content: The NRF5340-QKAA-R is a Bluetooth Processor chip...NRF5340-QKAA-R datasheet:https://docs-be.nordicsemi.com/bundle/ps_nrf5340/page/nRF5340_PS_v1.6.pdf?_LANG=enusPages 52 and 53 appear to be suggesting that there are switch mode regulators inside the NRF5340?It says that they are for use when the internal LDO's aren't efficient enough, and recommendsadding the inductors shown there for use when the "DC/DC" function is wanted.So does it really have a switch mode regulator controller inside it (looks like two of them?)I cant see anything inside it that draws more than a few mA, so cant understand why they are putting switch mode regulators inside it?

author: TimFox
author_rank: Super Contributor
timestamp: September 29, 2025, 10:11:19 pm
content: See section 4.7 of the datasheet.Apparently, you can run the device in "DC/DC" mode, which must be switching since it requires external inductors.However, there is a higher-power-dissipation "LDO" mode which does not use those inductors.Section 4.7.1 discusses the connection changes for "DC/DC" or "LDO" modes.I think it's good that in this modern era a manufacturer allowsnotusing switching that interferes with RF operations.

author: makebit
author_rank: Unknown
timestamp: September 30, 2025, 07:11:51 am
content: Thanks, so you would recomend that the DCDC is not used if the 2.4GHz radio transceiver is used?It does seem very odd them putting a switcher in it (two of them) when nothing in the chip pulls that much current at all.The 2.4GHz radio seems to pull the highest current at 5mA, and you wouldnt want a switcher for that....and especially not with it being the 2.4GHz radio.

author: tszaboo
author_rank: Super Contributor
timestamp: September 30, 2025, 08:02:11 am
content: Quote from: makebit on September 30, 2025, 07:11:51 amThe radio interface doesn't get upset if you run the micro from a well designed DC-DC controller. The TX power consumption figures on the front page are likely measured for the 5V supply, it would be about 3 times as much if you run the radio from an LDO. If your product is battery powered, every little bit of energy saving matters.

author: makebit
author_rank: Unknown
timestamp: September 30, 2025, 09:09:28 am
content: Thanks, i had been partly assuming that the on-chip SMPS stages were for supplying power to things off the chip, but as you kindly say, its actually for powering things on the NRF5340 itself.

author: tszaboo
author_rank: Super Contributor
timestamp: September 30, 2025, 09:12:15 am
content: Quote from: makebit on September 30, 2025, 09:09:28 amOn the chip, for sure. But You have to go through the reference manual and application notes though. I'm not that familiar with the NRF chips.

author: makebit
author_rank: Unknown
timestamp: September 30, 2025, 09:52:11 am
content: Yes, i am wondering if they only want people to use the internal SMPS if say, the only available external rail is 24V or so, and then it would be good to have a switcher to drop down to 3V3 or whatever.....i am wondering if a board already has a 5V rail outside the NRF5340, then would it really be worth using the internal SMPS's to go from 5V to 3V3 at 5mA, say?I mean, SMPS's draw their own bias current to operate as SMPS's, and they usually draw more bias current than a LDO.Also, SMPS's usually operate in burst mode in light load, which isnt that beneficial.

author: nali
author_rank: Frequent Contributor
timestamp: September 30, 2025, 10:06:22 am
content: QuoteI queried this with Nordic (54L series). They say the minimum supply current draw using LDO was in the order of 70-100uA which is pretty high if you're using battery power. Compare that to the operating power consumption in the DS.Note the regulators are for the internal core voltage which will be lower than the supply, 1.2V in the case of the 54Lxx I'm currently using. The 5340 is a dual core device so two regs makes sense.

author: tszaboo
author_rank: Super Contributor
timestamp: September 30, 2025, 10:12:03 am
content: Quote from: makebit on September 30, 2025, 09:52:11 amIf you want to run this from USB, then probably not.I see that the RF probably works from 1.8V, which is significantly less than 3.3VSo if you want a battery powered gadget, powered by coin cell, your DC-DC can extend the battery life like 40%. It's quite significant difference. The SMPS inside this chip is probably going to be very efficient. They designed it for example Bluetooth earbuds, it's the difference of having 4 or 6 hours battery life, for only one tiny SMD part.