bq3285LC

The CMOS bq3285EC/LC is a lowpower microprocessor peripheral providing a time-of-day clock and 100-year calendar with alarm features and battery operation. The architecture is based on the bq3285/7 RTC with added features: low-voltage operation, 32.768kHz output, and an extra128bytesofCMOS.


A 32.768kHz output is available for sustaining power-management activities. The bq3285EC 32kHz out-put is always on whenever V_CC is valid. For the bq3285LC, the output is on when the oscillator is turned on. In V_CC standby mode, the 32kHz is active, and the bq3285LC typically draws 100A while the bq3285EC typically draws 300A. Wake-up capability is provided by an alarm interrupt, which is activein battery-backup mode. In battery
backup mode, current drain is less than 500nA.


The bq3285EC/LC write-protects the clock, calendar, and storage registers during power failure. A backup battery then maintains data and oper-ates the clock and calendar.


The bq3285EC/LC 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 backupbattery.


The bq3285EC is intended for use in 5V systems. The bq3285LC is intended for use in 3V systems; the bq3285LC, however, may also operate at 5V and then go into a 3V power-down state, write-protecting asifina3Vsystem.