Low-power microcontroller (MCU) for battery-powered data loggers
Battery-powered logging · Sleep current with RTC, active µA/MHz, ADC channels, and the SD-card save events that dominate the battery budget
In a battery-powered data logger the microcontroller wakes on a real-time clock, reads its sensors through the ADC or a serial bus, stores the readings and returns to sleep, so its sleep current with the clock running, its active current per MHz and the way it drives storage decide how long the battery lasts. Ask three things first: what the MCU draws asleep with the RTC and RAM retained, what it draws while sampling, and how much of the battery budget the storage writes will take.
Low-power microcontrollers selected as the control unit of battery-powered data loggers — sleep and stop currents with RTC, wake-up and sampling peripherals, and their interaction with SD-card or flash storage. General-purpose 8-, 16- and 32-bit MCUs, including wireless and mixed-signal MCUs, are covered on the Microcontrollers (CPU / MCU) page; complete data loggers, sensors and storage cards are outside this page except where they set the MCU's power budget.
CNFX editorial research · Sources checked October 12, 2026 · 3 sources
Compare sleep current with the RTC running and active current per MHz
Renesas lists the RL78/G23 at 41 µA/MHz in CPU operation and 210 nA in stop mode with 4 KB of SRAM retained, with a snooze-mode sequencer that it says significantly reduces power during intermittent operation. The family runs from 1.6 V to 5.5 V at up to 32 MHz, offers up to 768 KB of program flash, 48 KB of SRAM and 8 KB of data flash, an RTC, low-voltage detection, and 12-bit A/D converter channels (26 listed). [1]
Ambiq lists its Apollo3 Cortex-M4 at 6 µA/MHz executing from flash or RAM at 3.3 V and 1 µA in deep sleep with the RTC at 3.3 V, up to 48 MHz (96 MHz performance), up to 1 MB of flash and 384 KB of RAM, a 14-bit ADC with 15 selectable inputs at up to 2.67 MS/s, a temperature sensor of ±3 °C after calibration, a 32.768 kHz crystal oscillator and an operating range of 1.755–3.63 V and −40 to 85 °C. [2]
Editorial note: the two sleep figures are stated under different conditions — 210 nA in stop with 4 KB SRAM retained against 1 µA in deep sleep with the RTC — so ask each maker for sleep current under your own conditions: RTC on, the RAM you must retain, the wake sources you need and your supply voltage.
Give the supplier the logging interval, the sensors and their interfaces (analog, I²C, SPI, UART), the ADC resolution and channel count needed, the storage medium and write interval, the battery chemistry, capacity and voltage range, the target life, the temperature range, and the package and pin count you can place.
02
Budget the SD-card save events, not just the MCU's sleep current
Bradley and Wright of Newcastle University measured an SD-card data logger built on an Atmega328P and report, in IEEE Access, that with the bare chip in sleep a 2400 mAh battery could theoretically last over 10 years, but adding an SD card cut that to 3 months; every initialisation and saving event took up to 200 ms with current spikes up to 80 mA. [3]
They found that adding a micro SD card reader raised the minimum sleep current of the Atmega328P from 120 nA (5 V, 16 MHz) and 97 nA (3.3 V, 8 MHz) to 800 µA and 750 µA; switching the card reader's ground through a BS170 MOSFET brought sleep current back down to 21.1 µA and 18.6 µA, at the cost of reinitialising the card on every wake cycle. Combining power gating with proper initialisation and timing of saves, they report a logger measuring every two seconds with a one-year battery life. [3]
Editorial calculation: a 2400 mAh battery over one year (8,760 h) allows an average of 2400 ÷ 8,760 ≈ 0.274 mA, or 274 µA. Treating one save as the worst case of 80 mA for 200 ms gives 80 × 0.2 = 16 mA·s per save, so saves alone would use the whole budget at any save interval shorter than 16 ÷ 0.274 ≈ 58 s — far above the MCU's own sleep current in the Renesas and Ambiq listings. [3][1][2]
03
MCU blocks a logger relies on
Block
Role in the logger
Published example
Real-time clock and 32.768 kHz oscillator
Wakes the MCU at each logging interval.
Apollo3: RTC and 32.768 kHz crystal oscillator; 1 µA deep sleep with RTC. [2]
Values to put in the MCU part of a logger design brief
Active and sleep current only mean something with their conditions attached — clock, voltage, RAM retained and RTC on or off — so record those next to every figure.
Field
Published values and meaning
Ask the supplier for
Supply voltage (V)
RL78/G23: 1.6–5.5 V; Apollo3: 1.755–3.63 V. [1][2]
Range across battery discharge.
Core clock frequency (MHz)
RL78/G23 up to 32 MHz; Apollo3 up to 48 MHz. [1][2]
Shanghai TX Semiconductor lists a microcontroller (MCU) category next to its LDO, Hall-sensor and driver ICs.
Shanghai TX Semiconductor Sci-Tech Co., Ltd.
Manufacturing site to be confirmed for the order
Lists a microcontroller (MCU) product category alongside LDO regulators, Hall-effect sensor ICs and driver ICs; no MCU model specifications were shown on the page reviewed.
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
How low can a data logger MCU's sleep current go?
Renesas lists 210 nA in stop with 4 KB SRAM retained for the RL78/G23; Ambiq lists 1 µA in deep sleep with the RTC for Apollo3. [1][2]
Why does an SD card shorten logger battery life?
Bradley and Wright measured up to 200 ms at up to 80 mA per save and a sleep current raised to 750–800 µA by the card reader. [3]
How can the SD card's drain be reduced?
By switching the card off between saves with a MOSFET and timing saves carefully; the Newcastle study reports one year of logging every two seconds. [3]
Sources and what still needs a direct check
Sources checked 2026-10-12. Renesas and Ambiq describe their own low-power MCUs; Bradley and Wright's IEEE Access paper (Newcastle University) measures the power drawn by an MCU-based SD-card data logger.
