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4-wire Serial Interface Real Time Clock (RTC) Module

Product Specifications

The R2045 is a real-time clock module, built in CMOS real-time clock IC and crystal oscillator, connected to the CPU by four signal lines, CE, SCLK, SI, and SO, and configured to perform serial transmission of time and calendar data to the CPU. The oscillation frequency is adjusted to high precision (0±5ppm: 13 sec. per month at 25°C). 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. 0.48µA 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 two selectable supply voltage monitoring threshold settings.

The 32-kHz clock output function (N-channel Open drain output) is intended to output sub-clock pulses for the external microcomputer. The oscillation adjustment circuit is intended to adjust time by correcting deviations in the oscillation frequency of the crystal oscillator.


Built in crystal unit 32.768 kHz, The oscillation frequency is adjusted to high precision (0±5ppm: at 25°C)
Timekeeping supply voltage 1.15 V to 5.5 V
Supply Current Typ. 0.48 µA (VDD=3V)
Connected to the CPU Four signal lines (CE, SCLK, SI, and SO)
Functions 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
With Oscillation halt sensing Flag to judge the validity of internal data
Supply voltage monitoring circuit with two supply voltage monitoring threshold settings
Automatic identification of leap years up to the year 2099
Selectable 12-hour and 24-hour mode settings
Built-in Circuits Oscillation adjustment circuit for correcting temperature frequency deviation or offset deviation
Clock Output 32.768 kHz (N-channel open drain output)
Package SOP14



SOP1410.1 mm × 7.4 mm
1 NC
3 32KOUT
4 NC
7 CE
8 NC
9 NC
11 VSS
12 SI
13 SO
14 NC

R2045 for Consumer


  • Home appliances such as refrigerators, rice cookers, and electric pots
  • Digital appliances such as laptops, digital TVs, DSCs, camcorders, mobile phones, and private LAN system
  • Office appliances such as copiers, printers, facsimiles, scanners, and projectors


R2045S operate PRODUCT LONGEVITY PROGRAM (ten-year supply is maintained as of January, 2016).
This program has been introduced to help customers select the most appropriate part for applications that require long life cycles.


Product Name   Package Quantity per Reel
R2045S-E2-F ConsumterPLP SOP14 1,000



Technical Support

Package *1 Reliability *2
SOP14 R2045S

*1: The package file includes package dimensions, taping specifications, taping reels dimensions.
*2: Reliability file includes a reliability test report and a reflow profile.

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