Ultra-Low-Power RTC Selection: RV-3028-C7 vs DS3231 vs PCF8563
For battery devices, an RTC's timekeeping current drives battery life. This article compares Micro Crystal's RV-3028-C7, the DS3231, and the PCF8563 on power, accuracy, and best-fit use, to help you pick the right real-time clock.
Why RTC power matters for battery devices
A real-time clock (RTC) keeps time while the main system is off, powered by a coin cell or supercapacitor. Its timekeeping current directly sets how long that backup lasts — for wearables, smart meters, and asset trackers, a few hundred nA can mean years of difference.
So the two key metrics for a low-power RTC are timekeeping current and accuracy (ppm).
Comparing the three RTCs
RV-3028-C7 (Micro Crystal): ~45nA timekeeping current, ~±1ppm after factory calibration, with an integrated crystal in a tiny package — one of the lowest-power I²C RTCs available.
DS3231 (Maxim/ADI): ~840nA timekeeping current; its big advantage is an integrated temperature-compensated crystal (TCXO) that holds high accuracy across a wide temperature range.
PCF8563 (NXP): ~250nA timekeeping current, basic features, cost-friendly — a common general-purpose RTC.
How to choose
If battery life comes first (wearables, IoT sensors, asset trackers): choose the RV-3028-C7 — 45nA timekeeping greatly extends backup time, and its integrated crystal saves an external part and calibration.
If wide-temperature accuracy comes first (industrial, outdoor, metering): choose the DS3231 — its TCXO stays stable over temperature, at the cost of higher power.
Note the RV-3028 and DS3231/PCF8563 have different pinouts, so a swap means re-layout and a firmware port.
Sourcing and selection support
JLink Technology is an authorized distributor for Switzerland's Micro Crystal, supplying ultra-low-power I²C RTC modules such as the RV-3028-C7 and RV-8263-C7 (integrated crystal, no external part).
If you are selecting an RTC for a battery device, or want a lower-power alternative to an existing DS3231/PCF8563, send us your requirements — we will help with selection and reply with stock, pricing, and lead time.
Products mentioned
RV-3028-C7 Extreme Low Power I²C RTC Module
The RV-3028-C7 is one of the industry's most power-efficient RTC modules, drawing typically just ~45 nA. It integrates a tuned crystal, offers an I²C interface, and includes alarm, timer, and event logging — ideal for coin-cell powered wearables, meters, and IoT applications needing long battery life.
RV-8263-C7 I²C RTC Module
The RV-8263-C7 is a low-power I²C RTC module with an integrated 32.768 kHz crystal, offering alarm, countdown timer, and clock output (CLKOUT). Its compact package suits consumer electronics, appliances, and industrial timekeeping.
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