3 Volt/5 Volt Serialized Real-Time Clock with NV RAM Control

Please check latest availability status for a specific part variant.


The DS1688/DS1691 is a real-time clock (RTC) designed as a successor to the industry standard DS1285, DS1385, DS1485, and DS1585 PC real time clocks. This device provides the industry standard DS1285 clock function with the new feature of either +3.0 or +5.0V operation and automatic backup and write protection to an external SRAM. The DS1688 also incorporates a number of enhanced features including a silicon serial number, power on/off control circuitry, 114 bytes of user NV SRAM, power on elapsed timer, and power cycle counter.

Key Features

Incorporates industry standard DS1287 PC clock plus enhanced features:
  • +3 or +5V operation
  • 64-bit Silicon serial number
  • 64-bit customer specific ROM or additional serial number available
  • Power control circuitry supports system power on from date/time alarm or key closure
  • Automatic battery backup and write protection to external SRAM
  • Crystal select bit allows RTC to operate with
  • 6pF or 12.5pF crystal
  • 114 bytes user NV RAM
  • Auxiliary battery input
  • RAM clear input
  • Century register
  • 32kHz output for power management
  • 32-bit VCC powered elapsed time counter
  • 32-bit VBAT powered elapsed time counter
  • 16-bit power cycle counter
  • Compatible with existing BIOS for original DS1287 functions
  • Available as IC (DS1688) or stand-alone module with embedded battery and crystal (DS1691)
  • Timekeeping algorithm includes leap year compensation valid up to 2100

Technical Documents

App Note 499 Using the Multiplex Bus RTC Extended Features

Quality and Environmental Data

Product Reliability Reports: DS1691.pdf 
Lead-Free Package Tin (Sn) Whisker Reports

Additional Resources

RTC Calculator
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

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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