Best Low-Power Microcontrollers for Battery-Powered IoT Projects

Hi,

Lowest power in standby might not be all too relevant, since a lot more power is required for processing and transmitting (or receiving).

You probably need to do some back-of-envelope calculations (i.e. do it in Excel or similar) to see how long you think your project can run for, based on the battery you plan to use, frequency of transmissions and so on. The microcontroller datasheets will specify the current consumption in the various microcontroller active and sleep modes.

You might find that the difference between (say) 0.5 uA and 1 uA non-active-state consumption might be "in the noise" - whether that's the case or not, only you will know once you do basic modeling.

Ambiq is worth a look. Probably the lowest power Cortex M4 with built-in BLE.

That’s a great point! I hadn’t fully considered how processing and transmission could outweigh standby power consumption. I’ll definitely do some rough calculations to estimate the overall power usage based on my battery capacity and transmission frequency. Looking at the datasheets for active and sleep current should give me a clearer picture of what to expect. You’re also right that the difference between 0.5 µA and 1 µA in standby might not be as significant as it seems in the bigger picture. I’ll model a few different scenarios and see what makes the most sense for my project. 

Thanks for the suggestion! I’ve come across Ambiq’s Apollo series but haven’t looked into them in detail. If they offer ultra-low power with built-in BLE, they might be a great fit for my project. I’ll check out their specs and see how they compare to other options. Appreciate the recommendation!

Hi,

Both Nordic Semi and Ambiq micro series are known for their low power chips for Bluetooth. But it varies from case to case which one might be suitable for your application.

For example, I was working on testing low-power design on Nordic nRF52 series and found that it could reach upto 6uA while the device is advertising on BLE channels.

I achieved this low power by increasing the adv interval, reduce the RAM usage by disabling unused RAM, disable unused paripherals, using on chip DC-DC regulator to power the chip instead on LDO and using external low-freq crystal to read low power design. This can be verified using Nordic PPK2 or similar. 

You can try to upload the hex file to your nRF52 based board and check yourself.

Low Power consumption for nRF52 series of devices - Nordic Q&A - Nordic DevZone - Nordic DevZone

You can also look at other vendors in Bluetooth space if you want to have a look. For example Silcon labs, STM32 etc. If you need WiFi + BLE on a single chip and want to reduce overall BOM ESP32 can also be a look.

So totally depends on your application.

Thanks so much for sharing your experience with the nRF52 series! Your tips on optimizing power consumption are really helpful, and I appreciate the detailed breakdown. I’ll definitely explore these options and also check out other vendors like Silicon Labs and STM32. Really appreciate your input!

There's no one-size-fits-all here.

Compare some applications:

1) a device that tracks multiple interactions between individuals to establish contact patterns and associations ( a bit like Covid contact tracking) so it must transmit a message every few seconds and receive messages with sub 1ms latency.

2) a remote water treatment monitoring station which must gather data continuously and send messages over  a long range perhaps once per hour or less and will receive messages at even longer intervals.

3) an air conditioning sensor which must transmit a few bytes of data at approx 5 minute intervals and has no need to receive data at all, but needs a 10 year battery life.

4) a shelf edge label which must receive data every few days, cost almost nothing and have a 10 year life.

All are low power applications but with completely different requirements.

There is no best processor or SOC that would be good in all these instances.

To get useful advice you need to provide more detail about the application.

To add to Shabaz's point about idle current - wild claims are made about chip idle currents but before you worry too much between 100nA and 10uA, check out the leakage current of any capacitors you might consider placing across the power rails and the battery's response to sudden changes of current.

There is an interesting article here:

https://www.ganssle.com/reports/ultra-low-power-design.html

I don't agree with every word of it but reading and understanding it will give you a good start.

MK