Watchdog Timekeepers

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The DS1284/DS1286 watchdog timekeepers are self-contained real-time clocks, alarms, watchdog timers, and interval timers in a 28-pin JEDEC DIP and encapsulated DIP package. The DS1286 contains an embedded lithium energy source and a quartz crystal, which eliminates the need for any external circuitry. The DS1284 requires an external quartz crystal and a VBAT source, which could be a lithium battery. Data contained within 64 8-bit registers can be read or written in the same manner as byte-wide static RAM. Data is maintained in the watchdog timekeeper by intelligent control circuitry that detects the status of VCC and write protects memory when VCC is out of tolerance. The lithium energy source can maintain data and real time for over 10 years in the absence of VCC. Watchdog timekeeper information includes hundredths of seconds, seconds, minutes, hours, day, date, month, and year. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including correction for leap year. The DS1284/DS1286 operate in either 24-hour or 12-hour format with an AM/PM indicator. The devices provide alarm windows and interval timing between 0.01 seconds and 99.99 seconds. The real-time alarm provides for preset times of up to one week.

Key Features

  • Keeps Track of Hundredths of Seconds, Seconds, Minutes, Hours, Days, Date of the Month, Months, and Years; Valid Leap Year Compensation Up to 2100
  • Watchdog Timer Restarts an Out-of-Control Processor
  • Alarm Function Schedules Real-Time-Related Activities
  • Embedded Lithium Energy Cell Maintains Time, Watchdog, User RAM, and Alarm Information
  • Programmable Interrupts and Square-Wave Outputs Maintain JEDEC Footprint
  • All Registers are Individually Addressable via the Address and Data Bus
  • Accuracy is Better than ±1 Minute/Month at +25°C
  • Greater than 10 Years of Timekeeping in the Absence of VCC
  • 50 Bytes of User NV RAM
  • -40°C to +85°C Industrial Temperature Range

Technical Documents

App Note 504 Design Considerations for Maxim Real-Time Clocks

Additional Resources

Other Watchdog Clocks
Product Reliability Reports: DS1286.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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