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• PCF2127A Datasheet
• PCF2129A Datasheet
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Highly accurate RTCs with embedded quartz crystal

The NXP Semiconductors PCF2127A and PCF2129A are CMOS Real Time Clock and Calendar (RTC) devices with integrated Temperature Compensated Crystal Oscillator (TCXO) and a 32.768 kHz quartz crystal optimized for very high accuracy and very low power consumption. The NXP Semiconductors PCF2127A RTC has 512 bytes of general purpose static RAM. The PCF2127A and PCF2129A RTCs include features such as a selectable I²C-bus or SPI-bus, a backup battery switch-over circuit, a programmable watchdog function, a timestamp function, and more. Both the PCF2127A and PCF2129A also feature typical accuracy of ±3 ppm from -15 ºC to +60 ºC. These NXP RTC devices with integrated TCXO and quartz crystal are ideal for a variety of applications, including electronic metering for electricity, water, and gas, timekeeping instruments with high precision, GPS equipment to reduce time to first fix, applications requiring accurate process timing, and products with long automated unattended operation time.

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Equipped with a temperature-compensated crystal oscillator, these RTCs eliminate the need for a heated quartz or GPS frequency references.

• Time keeping with accuracy of ±3 ppm typically
  
• Fully integrated quartz oscillator
  
• Time-stamp function
  
• Battery switch-over circuit
  
• System reset generation
  
• 512 bytes of RAM (PCF2127)
  
• Factory calibrated
  
• Clock operating down to 1.2 V
  
• Low supply current: 650 nA at 3 V
  
• 1-MHz Fast-mode Plus I2C-bus and 6-MHz SPI interface

• Very accurate time references
  
• Accurate switching
  
• Utility meters
  
• Industrial applications
  
• HVAC equipment
  
• GPS, shorter cold start-up time (TTFF)
  
• Gaming machines
  
• Alarm systems
  
• Token for access control
  
• Cellular infrastructure