Y2K-Compliant Watchdog RTC with NV Control

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The DS1500 is a full-function, year 2000-compliant, real-time clock/calendar (RTC) with an alarm, watchdog timer, power-on reset, battery monitors, 256 bytes of on-board nonvolatile (NV) SRAM, NV control for backing up an external SRAM, and a 32.768kHz output. User access to all registers within the DS1500 is accomplished with a byte-wide interface as shown in Figure 7. The RTC registers contain century, year, month, date, day, hours, minutes, and seconds data in 24-hour binary-coded decimal (BCD) format. Corrections for day of month and leap year are made automatically.
DS1500: Typical Operating Circuit DS1500: Typical Operating Circuit Enlarge+

Key Features

  • BCD-Coded Century, Year, Month, Date, Day, Hours, Minutes, and Seconds with Automatic Leap-Year Compensation Valid Up to the Year 2100
  • Programmable Watchdog Timer and RTC Alarm
  • Century Register; Y2K-Compliant RTC
  • Automatic Battery Backup and Write Protection to External SRAM
  • +5V or +3.3V Operation
  • Precision Power-On Reset
  • Power-Control Circuitry Supports System Power-On from Date/Day/Time Alarm or Key Closure
  • 256 Bytes User NV RAM
  • Auxiliary Battery Input
  • Accuracy Better than ±1 Minute/Month at +25°C
  • Day-of-Week/Date Alarm Register
  • Battery Voltage-Level Indicator Flags
  • Optional Industrial Temperature Range: -40°C to +85°C


  • Battery-Backed Systems
  • Consumer Electronics
  • Office Equipment
  • Remote Systems
  • Telecom Switches
Product Reliability Reports: DS1500.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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