Description

Product Category: Real-time Clocks (RTC)

The CMOS bq4285 is a low-power microprocessor peripheral providing a time-of-day clock and 100-year calendar with alarm features and battery operation. It is a direct clock/calendar replacement for IBM AT-compatible computers and other applications, closely matching MC146818A pin configuration. The bq4285 has 114 bytes of general nonvolatile storage and allows automatic backup and write protect control to external SRAM. With a fast cycle time of 160 ns, it enables fast bus operation. It offers selectable Intel or Motorola bus timing (PLCC) and Intel bus timing (DIP and SOIC). The load under battery operation is less than 0.5 µA. The clock/calendar and control occupy 14 bytes of memory. The calendar includes day of the week, day of the month, months, and years with automatic leap-year adjustment. The time of day is displayed in seconds, minutes, and hours in either 12- or 24-hour format, with optional daylight saving adjustment. Data can be stored in BCD or binary format. The bq4285 also features a programmable square wave output and three individually maskable interrupt event flags: periodic rates from 122 µs to 500 ms, time-of-day alarm once per second to once per day, and end-of-clock update cycle. It is available in a 24-pin plastic DIP or SOIC package.

Specifications and features

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;

Automatic backup and write protect control to external SRAM;

160 ns cycle time allows fast bus operation;

Selectable Intel or Motorola bus timing (PLCC), Intel bus timing (DIP and SOIC);

Less than 0.5 µA load under battery operation;

14 bytes for clock/calendar and control;

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;

BCD or binary format for clock and calendar data;

Programmable square wave output;

Three individually maskable interrupt event flags: periodic rates from 122 µs to 500 ms, time-of-day alarm once per second to once per day, and end-of-clock update cycle;

24-pin plastic DIP or SOIC.

Application Scenarios

The CMOS bq4285 Real-time Clock (RTC) is designed as a peripheral for microprocessors, particularly for IBM AT-compatible computers. It can also be used in other applications that require a time-of-day clock and a calendar with alarm features. The bq4285 is suitable for devices that need accurate timekeeping while operating on battery power, thanks to its low-power consumption of less than 0.5 µA. With its 114 bytes of general nonvolatile storage, it offers storage space for various data needs. The bq4285 is a versatile RTC solution, allowing programmable square wave outputs and supporting interrupt event flags for time-sensitive applications. Its compatibility with DS1285 and MC146818A pin configuration simplifies system integration. The bq4285 is available in 24-pin plastic DIP or SOIC packages, making it easy to incorporate into various designs.

Comparison

- Low-power operation with less than 0.5 µA load under battery operation.

- 114 bytes of general nonvolatile storage for data retention.

- Selectable Intel or Motorola bus timing for flexible integration.

- Programmable square wave output and interrupt event flags for time-sensitive applications.

- Compatibility with DS1285 and MC146818A pin configuration.

- Available in 24-pin plastic DIP or SOIC packages for easy incorporation into designs.

- Limited storage capacity compared to some other RTC solutions.