BQ3287E (OBSOLETE)

RTC Module With 242x8 NVSRAM, Alarm Wake-up, RAM Clear Input on EA Version

This Product is no longer available

Replaced By BQ3285E – The device has SIMILAR FUNCTIONALITY but is not functionally equivalent to the compared device.  

TI does not recommend using this part in a new design. This product continues to be in production to support existing customers.

Description

The CMOS bq3287E/bq3287EA 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 242 bytes of general nonvolatile storage. A 32.768kHz output is available for sustaining power-management activities. Wake-up capability is provided by an alarm interrupt, which is active in battery-backup mode. The bq3287EA version is identical to the bq3287E, with the addition of the RAM clear input.

The bq3287E is a fully compatible real-time clock for IBM AT-compatible computers and other applications. The bq3287E write-protects the clock, calendar, and storage registers during power failure. The integral backup energy source then maintains data and operates the clock and calendar.

As shipped, the real time clock is turned off to maximize battery capacity for in-system operation.

The bq3287E is functionally equivalent to the bq3285E, except the battery (16,20) and crystal pins (2,3) are not accessible. These pins are connected internally to a coin cell and quartz crystal. The coin cell is sized to provide 10 years of data retention and clock operation in the absence of power. For a complete description of features, operating conditions, electrical characteristics, bus timing, and pin descriptions, see the bq3285E data sheet.

Features

  • Direct clock/calendar replacement for IBM\xAE AT-compatible computers and other applications
  • Functionally compatible with the DS1287/DS1287A and MC146818A/ MC146818B
  • 242 bytes of general nonvolatile storage
  • Provides a 32.768kHz output for power management
  • System wake-up capability-alarm interrupt active in battery-backup mode
  • Integral lithium cell and crystal
  • 160 ns cycle time allows fast bus operation
  • 14 bytes for clock/calendar and control
  • Time of day in seconds, minutes, and hours
    • 12- or 24-hour format
    • Optional daylight saving adjustment
  • Calendar in day of the week, day of the month, months, and years with automatic leap year 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
  • Better than one minute per month clock accuracy

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