power regulator for nRF52 series

[Lakerno]

Any recommendations of power ic to be used in an nRF52 based system? I am thinking of using DC-DC converter from LTC3553 . Is DCDC converters a good choice for powering nRF52 chip? cds.linear.com/.../3553fc.pdf

[jcondon]

What is your expected power source? Are you powering anything other than the nRF52? If so, what are your current and voltage requirements for those?

[Lakerno]

expected power source is a USB charger or Li Ion battery. I have an acclertometer and biomedical frontend.

[Øyvind Karlsen]

Hi,

The way I am interpreting it you either want a 3V battery or a 5V charger connected to your mains outlet. Not knowing the voltage requirements of your accelerometer and biomedical frontend I will only comment on the 52 part.

Have a look at the documentation for the power managerment module for the nRF52 it covers some information on the internal LDO and DC/DC regulators. The nRF52 can take supply voltages from 1.7 to 3.6 V, if you want to use a higher supply voltage than this you will need to down-convert it before passing it to the 52.

Generally you will have some loss in your DC-DC converter, so for a low loss application you will often want to use the built in voltage regulator systems in the nRF52 along with a battery. If you want to reduce the voltage from 5V to 3V3, and can accept losses, you can use nearly any voltage regulator. You can take a look at how the USB voltage is being regulated from 5V to 3V3 in the preview development kit.

One final note is that you might also experience some deteriorated performance while powering the nRF52 with an external voltage regulator, this is because down- and up-converters utilize high frequency switching which add noise to a system.

Hopefully this answers your question, best regards,

Øyvind

[Lakerno]

The acclerometer can be powered by 1.7-3.6V supply The biomedical frontend (www.ti.com/.../sbas566a.pdf) needs 2 different supply . ie 1) Analog Supply of 2.7-5.2V and 2) Digital supply 1.8-3.6V

I am using a 3.7V Lithium ion battery /USB power to power the device. So I thought of using LTC3553 (link in the original post) to power all the devices. The analog supply of the TI chip will be powerd by the LDO output of the LTC3553 (at 3V) and DC/DC converter output of LTC3553 to power acclerometer, Digital Vdd of Ti Chip and nRF52 (3V/1.8V). Didnt know that nrf52 had internal regulators .

So in my case, how would you recommend me to power. Since nRF52 can only take upto 3.6V, I do need to reduce the 3.7V voltage level from li-ion battery before I can power it. Is that correct?

[Øyvind Karlsen]

Yes you do need to reduce to 3.6V or less. Be aware that even though your Li-Ion battery is rated at 3.7V it will very likely have more than that at maximum charge, this means that you will risk frying your circuit. You can either look for a lower voltage battery, or you can use a voltage regulator like the one you have suggested.

Since you also need an analog supply for your other chip you might have to separate the two voltage levels galvanically.

Best regards,

Øyvind