RX-8731LC (Built-in EEPROM and Unique ID-ROM I2C-Bus Interface Real Time Clock Module)

  • Built in frequency adjusted 32.768kHz crystal unit.
  • Interface Type
    I2C-Bus interface (400 kHz)
  • Operating voltage range
    1.7V to 5.5V
  • •Wide voltage for timekeeping
    1.3V to 5.5V
  • Low backup current
    0.35µA / 3V(Typ.)
  • 32.768kHz frequency output function
    C-MOS output With Control Pin
  • The various functions include full calendar, alarm, timer

Complies with EU RoHS directive.


Block diagram

Block diagram


  • Built in EEPROM and ID-ROM
    • Built in 10Byte ( 80bit) EEPROM
    • Built in 6Byte ( 48bit ) ID-ROM
  • Programmable I/O ports
    • 4Programmable I/O ports
  • Interface Type
    • I2C-Bus high-speed bus specifications. (400kHz)
  • 32.768kHz frequency output function
    • FOUT pin output (C-MOS output), CL=30pF
    • FOE pin enables output on/off control.
    • Output frequency is selectable.
      < 32.768kHz, 1024 Hz, 1 Hz >
  • The various interrupt function
    • Alarm interrupt function
    • Timer interrupt function
    • Update interrupt function

Specifications *Refer to application manual for details.

Recommend Operating Conditions

Item Symbol Condition Min. Typ. Max. Unit
Power voltage VDD - 1.7 3.0 5.5 V
Clock voltage VCLK - 1.3 3.0 5.5 V
Operating temperature TOPR - -40 +25 +85 °C

Frequency characteristics

Item Symbol Condition Rating Unit
Frequency tolerance Δ f/f Ta=+25°C
5±23 * ×10-6
Oscillation start-up time tSTA Ta=+25°C
1Max. s
Ta=-40°C to +85°C
3Max. s

* Please ask for tighter tolerance. (Equivalent to ±1 minute of monthly deviation)

Current consumption characteristics

Item Symbol Conditions Min. Typ. Max. Unit
lBK fSCL=0 Hz / IRQ = OFF
FOUT: output OFF(Hi-z)
VDD=5V - 0.45 1.5 µA
VDD=3V - 0.35 1.4
l32k fSCL=0 Hz / IRQ = OFF
FOUT:32.768kHz output CL=30pF
VDD=5V - 8.0 16.0 µA
VDD=3V - 5.0 10.0


Pin function

Signal Name Input/Output Function
SCL Input Serial Clock input pin.
SDA Bi-directional Data input and output pin.
A 0 Input Device address A0 input pin.
FOUT Output FOUT pin is 32.768kHz clock output pin (C-MOS) that output control is possible.
FOE pin control the frequency output from FOUT pin with FSEL1-bit and FSEL0-bit.
FOE Input
/ IRQ Output Interrupt output pin. (N-ch open drain)
Bi-directional Programmable I/O ports.
VDD - Connected to a positive power supply.
GND - Connected to a ground.

Terminal connection / External dimensions

Terminal connection External dimensions

(Unit: mm)

Stop using the glue
  Any glue must never use it after soldering LC-package to a circuit board.
  This product has glass on the back side of a package.
  When glue invasions between circuit board side and glass side, then glass cracks by thermal expansion of glue.
  In this case a crystal oscillation stops.Consider glue abolition or glue do not touch to LC-package

Footprint (Recommended)


(Unit: mm)

To maintain stable operation, provide a 0.1uF by-pass capacitor
at a location as near as possible to the power source terminal of the crystal product (between Vcc - GND).

Page Top