Extending battery life with ultra-low-power real-time clock modules

Through those idle periods, the system still needs an accurate time base so that data carries correct timestamps, scheduled tasks run on time, and the device can reconcile its clock with network time when it reconnects. That responsibility belongs to the real-time clock (RTC). Because the RTC is often the only circuit that runs continuously, its current draw has a direct effect on battery life. Its accuracy matters just as much. A timekeeping error of 20 ppm equals roughly 1.7 seconds per day, or more than 10 minutes over a year. That level of drift is enough to disrupt billing intervals, event logs, and certificate validity checks in systems that cannot resynchronize often.

A traditional approach pairs an RTC function, either standalone or inside a microcontroller, with a discrete 32.768 kHz tuning-fork crystal. That works, but it requires care with load capacitance, drive level, and board layout, and the finished oscillator often needs calibration in production. An RTC module removes most of that effort by combining the crystal and the RTC circuit in a single hermetically sealed ceramic package, with the oscillator matched and calibrated at the factory.
Temperature is the other major variable. A tuning-fork crystal is most accurate near 25°C, and its frequency falls away along a parabolic curve as temperature moves in either direction, with errors exceeding 100 ppm at both ends of the industrial range. Temperature-compensated RTC modules correct for this with an integrated temperature sensor and digital compensation, a technique known as DTCXO (digital temperature compensated crystal oscillator), which holds accuracy to a few ppm across the full operating range.

For performance and application fit, the first figures to compare are timekeeping current and time accuracy, both at room temperature and across the operating range. Supply voltage also matters, particularly the minimum voltage at which the device keeps time, since it determines how long a backup battery or capacitor can hold the clock. Designers should also confirm the interface, I2C or SPI, and the functions the system needs, such as alarms, countdown timers, timestamp inputs, backup switchover, and nonvolatile user memory.
Environmental and mechanical requirements include the operating temperature range and, for vehicle electronics, the level of automotive qualification. An RTC module combines a quartz crystal with a semiconductor die, so it falls under AEC-Q104, the standard for multi-chip modules, which brings together the AEC-Q200 requirements for passive components and the AEC-Q100 requirements for semiconductors. Package size is often decisive in wearables and compact modules. On the sourcing side, it helps to know where pin-compatible options exist. Within the Micro Crystal portfolio, pin compatibility applies to variants that share a part number root, such as the RV-3028-C7 and RV-3028-C8, rather than across the RTC family as a whole, since each part number has its own pinout. Buyers also benefit from families with long lifecycle support.

IoT, embedded boards, and test equipment. The RV-3028-C7 is designed for systems where every nanoampere counts. It draws 45 nA at 3 V, is factory calibrated to ±1 ppm at 25°C, and keeps time from 1.1 V to 5.5 V. Automatic backup switchover with trickle charging, a 32-bit UNIX time counter, and user EEPROM suit sensor nodes, single-board computers, and data loggers that must hold accurate time through power interruptions.
Wearables. Where board area is the tightest constraint, the RV-3028-C8 offers the same function and pinout as the C7 version in a 2.0 x 1.2 x 0.6 mm package. Its 70 nA timekeeping current supports longer battery life, or a smaller battery, in smart rings, hearing aids, and fitness devices.
Energy and security. Utility meters depend on accurate time-of-use records, and security systems rely on precise event timestamps. The RV-3032-C7 uses DTCXO compensation to maintain ±2.5 ppm accuracy from -40°C to +85°C, includes an embedded 12-bit temperature sensor, and draws 160 nA. It supports operation up to +105°C in a 3.2 x 1.5 x 0.8 mm package.
Automotive and data center. The RV-8803-C7 pairs DTCXO compensation with 240 nA current consumption, delivering ±1.5 ppm accuracy from 0°C to +50°C and ±3 ppm from -40°C to +85°C, with operation extending to +105°C. An automotive grade version, identified by the QA suffix, supports vehicle electronics, while the standard version serves enterprise equipment that depends on accurate event logging.
Consumer electronics and appliances. For cost-sensitive, high-volume products, the RV-8263-C8 provides a compact RTC with a streamlined feature set and timekeeping down to 0.9 V. The related RV-8263-C7 offers the same I2C function in a 3.2 x 1.5 mm package, and the RV-8063-C7 and RV-8063-C8 provide SPI interface options.

Micro Crystal, a Swiss manufacturer of miniature quartz crystals, pairs its tuning-fork crystals with dedicated RTC circuitry to achieve low current and stable timekeeping in very small packages. Its portfolio spans ultra-low-power, high-accuracy, temperature-compensated, and ultra-small RTC modules, from consumer products to industrial and automotive systems.
To shorten selection, Micro Crystal offers an RTC Modules Overview with feature comparisons and application guidance, along with an interactive RTC Modules Parametric Table that filters devices by feature and explains the role of each one. Arrow supports these designs with authorized, traceable supply and lifecycle visibility.