R2221L-E2

Real Time Clock Overview

The R2221L-E2 is a CMOS real-time clock IC featuring a 2-wire serial interface (I2C) with SCL and SDA lines. It operates within a supply voltage range of 0.6V to 5.5V, maintaining ultra-low power consumption with a typical timekeeping current of 0.18µA at 3V in ECO mode. The device integrates time counters for seconds through years and calendar counters including automatic leap year identification up to 2099. It includes two alarm interrupt circuits, a periodic interrupt circuit with selectable frequencies, and a 32.768kHz clock output. The component is housed in a QFN018018-12 package measuring 1.8mm x 1.8mm x 0.43mm.

Real Time Clock Feature Summary

• Ultra-low power consumption: Typical timekeeping current of 0.18µA at VDD=3V in ECO mode.
• Dual alarm interrupts: Supports Alarm_W (week/hour/minute) and Alarm_D (hour/minute) settings.
• High-precision oscillation adjustment: Built-in capacitors allow correction of frequency deviations up to ±189ppm.
• Integrated monitoring: Includes power-on reset flag, oscillation halt sensing, and supply voltage monitoring.

Real Time Clock Applications

• Battery-backed systems requiring precise timekeeping
• Embedded devices utilizing I2C communication
• Applications needing periodic or alarm-based interrupt generation

Real Time Clock Procurement Notes

Verify the specific ordering suffix against the manufacturer's selection guide to confirm package type and reel quantity. The R2221L-E2 designation corresponds to the QFN018018-12 package with a standard reel quantity of 3000 pieces. Ensure compatibility with the required operating temperature range of -40°C to +85°C during procurement planning.

Real Time Clock Selection Notes

Select the R2221L-E2 when a compact QFN footprint is required compared to the TSSOP variant. Consider the ECO mode capability if minimizing standby current is critical, noting that this mode requires specific crystal equivalent series resistance values. Verify that the CPU interface supports the maximum SCL clock frequency of 400kHz for fast mode operation.

Real Time Clock Part Context

The R2221L-E2 belongs to the R2221x/R2223x family of 2-wire serial interface real-time clock ICs manufactured by Nisshinbo Micro Devices. This family shares core functionalities such as BCD format counting and alarm circuits, differing primarily in pin configurations and interrupt outputs between the R2221x and R2223x sub-series.

Real Time Clock Replacement Considerations

The R2223L-E2 is a functional alternative within the same family, offering similar specifications but with distinct interrupt pin assignments (INTRA/INTRB instead of INTR). Substitution requires verification of interrupt signal routing and register configuration compatibility.