BQ3285 RTC IC with 114x8 NVSRAM |

BQ3285 (NRND)

RTC IC with 114x8 NVSRAM

RTC IC with 114x8 NVSRAM - BQ3285


The CMOS bq3285 is a low-power microprocessor peripheral providing a time-of-day clock and 100-year calendar with alarm features and battery operation. Other features include three maskable interrupt sources, square wave output, and 114 bytes of general nonvolatile storage.

The bq3285 write-protects the clock, calendar, and storage registers during power failure. A backup battery then maintains data and operates the clock and calendar.

The bq3285 is a fully compatible real-time clock for IBM AT compatible computers and other applications. The only external components are a 32.768kHz crystal and a backup battery.


  • Direct clock/calendar replacement for IBM® AT-compatible computers and other applications
  • Functionally compatible with the DS1285
    • Closely matches MC146818A pin configuration
  • 114 bytes of general nonvolatile storage
  • 160ns cycle time allows fast bus operation
  • Selectable Intel or Motorola bus timing
  • Less than 0.5µA load under battery operation
  • 14 bytes for clock/calendar and control
  • BCD or binary format for clock and calendar data
  • Calendar in day of the week, day of the month, months, and years, with automatic leap-year adjustment
  • Time of day in seconds, minutes, and hours
    • 12- or 24-hour format
    • Optional daylight saving adjustment
  • Programmable square wave output
  • Three individually maskable interrupt event flags:
    • Periodic rates from 122us to 500ms
    • Time-of-day alarm once per second to once per day
    • End-of-clock update cycle
  • 24-pin plastic DIP or SOIC

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