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



Complies with EU RoHS directive. PB Free
  • 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.
  • * The I2C-BUS is a trademark of NXP Semiconductors.

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
    • When VDD deteriorates, internal source is switched to VBAT.
  • Timer function
    • Timer function can be set up between 1/4096 second and 4095 minutes.
  • Alarm function
    • Alarm function can be set to day of week, day, hour, and minute.
  • Temp. sensor function
    • The temperature data are output to a register by a temp. sensor function. (Bank.2_Add17h)

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.

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)

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