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R2221T/L, R2223T/L

2-wire Serial Interface Real Time Clock IC


Data Sheet

The R2221T/L,R2223T/L is a CMOS real-time clock IC connected to the CPU by two signal lines, SCL, SDA, and configured to perform serial transmission of time and calendar data to the CPU. The periodic interrupt circuit is configured to generate interrupt signals with six selectable interrupts ranging from 0.5 seconds to 1 month. The 2 alarm interrupt circuits generate interrupt signals at preset times. As the oscillation circuit is driven under constant voltage, fluctuation of the oscillator frequency due to supply voltage is small, and the time keeping current is small (TYP. 0.18µA at 3V). The oscillation halt sensing circuit can be used to judge the validity of internal data in such events as power-on; the supply voltage monitoring circuit is configured to record a drop in supply voltage below supply voltage monitoring threshold settings. The 32.768kHz clock output function (CMOS output with control pin) is intended to output sub-clock pulses for the external microcomputer. The oscillation adjustment circuit is intended to adjust time counts with high precision by correcting deviations in the oscillation frequency of the crystal oscillator. Since the package for these ICs are TSSOP10G (4.0 x 2.9 x 1.0: R2221T, R2223T) or QFN018018-12 (1.8 x 1.8 x 0.43: R2221L, R2223L), high density mounting of ICs on boards is possible.


Minimum Timekeeping supply voltage TYP:0.6 to 5.5v (Worst: 0.9V to 5.5v); VDD pin
Ultra low power consumption 0.18µA TYP at VDD=3V (0.65µA MAX.)
Two signal lines (SCL, SDA) required for connection to the CPU.
Time counters (counting hours, minutes, and seconds) and calendar counters (counting years, months, days, and weeks) (in BCD format)
Interrupt circuit configured to generate interrupt signals (with interrupts ranging from 0.5 seconds to 1 month) to the CPU and provided with an interrupt flag and an interrupt halt
2 alarm interrupt circuits (Alarm_W for week, hour, and minute alarm settings and Alarm_D for hour and minute alarm settings)
With Power-on flag to prove that the power supply starts from 0V
32-kHz clock output pin (CMOS push-pull output with control pin)
Supply voltage monitoring circuit with supply voltage monitoring threshold settings
Automatic identification of leap years up to the year 2099
Selectable 12-hour and 24-hour mode settings
High precision oscillation adjustment circuit
Built-in oscillation stabilization capacitors (CG and CD)
  • TSSOP10G (4.0mm x 2.9mm x 1.0mm: R2221T, R2223T)
  • QFN018018-12 (under development) (1.8mm x 1.8mm x 0.43mm: R2221L, R2223L)
CMOS process


  • Hand-held equipment
  • Copiers, Printers, Facsimiles, Scanners, Projectors
  • Communication equipment
  • Digital Home appliances
  • Water meter, Electric meter, Gus meter
  • Medical home equipment
  • Industrial equipment

Documents Download

Data Sheet Package Info. Mark Info. Quality Assurance Data
R2221T/L, R2223T/L QFN018018-12 R2221L Reliability
R2223L Reliability
TSSOP-10G R2221T Reliability
R2223T Reliability

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