bq4285

The CMOS bq4285 is a low-power microprocessor peripheral providing a time-of-day clock and 100-year calendar with alarm features and bat-tery operation. Other features include three maskable interrupt sources, square wave output, and 114 bytes of generalnonvolatilestorage.


The bq4285 write-protects the clock,calendar, and storage registers during power failure. A backup battery then maintains data and operates theclockandcalendar.


The bq4285 is a fully compatible real-time clock for IBM AT-compatible computers and other applications.The only external components are a 32.768kHz crystalandabackupbattery.


The bq4285 integrates a batterybackup controller to make a standard CMOS SRAM nonvolatile during power-fail conditions. During powerfail, the bq4285 automatically writeprotects the external SRAM and provides a V_CC output sourced from the clockbackupbattery.