RX8900SA :I2C-Bus Interface Real Time Clock Module
(Built-in 32.768 kHz-DTCXO, High Stability and Power Switching)

  • Built in frequency adjusted 32.768 kHz crystal unit and DTCXO.
  • Interface Type
    I2C-Bus interface (400kHz)
  • Interface voltage range
    2.5V to 5.5V
  • Temp. compensated voltage range
    2.0V to 5.5V
  • Clock supply voltage range
    1.6V to 5.5V
  • Selectable clock output(32.768 kHz, 1024 Hz, 1 Hz)
  • The various functions include full calendar, alarm, timer, temp. sensor function.
  • Epson prepared Linux driver for development
  • https://www5.epsondevice.com/en/information/support/linux_rtc/
    The registered trademark Linux® is used pursuant to a sublicense from LMI(Linux Mark Institute)

Complies with EU RoHS directive.


Block diagram

Block diagram


  • High Stability
    • UA ± 3.4 x 10-6 / -40 °C to +85 °C ( Equivalent to ±9 seconds of month deviation )
    • UB ± 5.0 x 10-6 / -40 °C to +85 °C ( Equivalent to ±13 seconds of month deviation )
    • UC ± 5.0 x 10-6 / -30 °C to +70 °C ( Equivalent to ±13 seconds of month deviation )
  • 32.768 kHz frequency output function
    • FOUT pin output (C-MOS output), CL=30 pF
    • Output selectable: 32.768 kHz, 1024 Hz, 1 Hz
  • Available automatic battery backup switch-over function
    • Charge from VDD to backup battery connected to VBAT is possible.
      VDD voltage drop(VDET3) detection and automatically switches to the backup battery.
      This circuit is optimal to backup with a secondary battery and a large capacitor.
  • Timer function
    • Timer period is adjustable in 1/4096 second from 4095 minutes
  • Alarm function
    • Available dual-alarm, weekly and monthly
  • Temp. sensor function
    • Available readout temperature data from embedded temp sensor. (Bank.2_Add17h)

Specifications (characteristics)

Refer to application manual for details.

Electrical Characteristics

Item Symbol Conditions Min. Typ. Max. Unit
Operating voltage VDD Interface voltage 2.5 3.0 5.5 V
Temp. compensated Voltage VTEM Temp. compensated voltage 2.0 3.0 5.5 V
Clock supply voltage VCLK Internal clock 1.6 3.0 5.5 V
Operating temperature TOPR No condensation -40 +25 +85 *3 °C
Stability Δ f/f UA Ta=-40°C to+85°C
±3.4 *1 x10-6
UB Ta=-40°C to+85°C
±5.0 *2
UC Ta=-30°C to+70°C
Current consumption(1) lDD1 fSCL=0Hz,/INT=VDD,
VDD=VBAT FOUT:OFF Temp. Compensation
interval 2.0 s.
VDD=5V - 0.72 1.5 µA
Current consumption(2) lDD2 VDD=3V - 0.70 1.4

*1 Equivalent to ±9 seconds of month deviation.
*2 Equivalent to ±13 seconds of month deviation.
*3 Please contact us about +85°C < TOPR

32.768 kHz-DTCXO Frequency temperature characteristics (Example)


Pin function

Signal Name I / O Function
T1(CE) input Use by the manufacture for testing.
( Do not connect externally.)
SCL input Serial clock input pin.
FOUT output The pin outputs the reference clock signal.
( CMOS output )
VBAT - Battery supply.
This pin has charge capability to backup battery.
VDD - Connected to a positive power supply
FOE input The input pin for the FOUT output control.
/ INT output Interrupt output (N-ch. open drain).
GND - Connected to a ground
T2(VPP) - Use by the manufacture for testing.
( Do not connect externally.)
SDA I/O Data input and output pin.

Terminal connection/External dimensions

Terminal connection External dimensions

(Unit: mm)

The metal case inside of the molding compound may be exposed on the top or bottom of this product.
This purely cosmetic and does not have any effect on quality, reliability or electrical specs.

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).

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