SPI Real-Time Clock/Calendar

PCF2123

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The PCF2123 is a CMOS Real-Time Clock (RTC) and calendar optimized for low power applications. Data is transferred serially via a Serial Peripheral Interface (SPI-bus) with a maximum data rate of 6.25 Mbit/s. An alarm and timer function is also available providing the possibility to generate a wake-up signal on an interrupt pin. An offset register allows fine tuning of the clock.

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Block Diagram

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PCF2123 Block Diagram

PCF2123 Block Diagram

Block diagram: PCF2123TS, PCF2123U

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Features

  • Real time clock provides year, month, day, weekday, hours, minutes, and seconds based on a 32.768 kHz quartz crystal
  • Low backup current while running: typical 100 nA at VDD = 2.0 V and Tamb = 25 ℃
  • Resolution: seconds to years
  • Watchdog functionality
  • Freely programmable timer and alarm with interrupt capability
  • Clock operating voltage: 1.1 V to 5.5 V
  • 3 line SPI-bus with separate, but combinable data input and output
  • Serial interface at VDD = 1.8 V to 5.5 V
  • 1 second or 1 minute interrupt output
  • Integrated oscillator load capacitors for CL = 7 pF
  • Internal Power-On Reset (POR)
  • Open-drain interrupt and clock output pins
  • Programmable offset register for frequency adjustment

Target Applications

  • Time keeping application
  • Battery powered devices
  • Metering
  • High duration timers
  • Daily alarms
  • Low standby power applications

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