Y2K Enhanced ACPI Compliant RTC IC W 240x8 NVSRAM, Alarm Wake-up 3.3V Op 32kHz Dedicated Output
The CMOS BQ3285LF is Y2K-Enhanced Real-Time Clock a low-power 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 RTC with added features: century bit, low-voltage operation, 32.768kHz output, 126 additional bytes of CMOS, two shadow Registers of last address used, and a day-of-month alarm to be compliant with the ACPI RTC specification.
A 32.768kHz output is available for sustaining power-management activities. The BQ3285LF 32kHz output is always on whenever VCC is valid. In VCC standby mode, the 32kHz is active, and the BQ3285LF typically draws 100uA. Wake-up capability is provided by an alarm interrupt, which is active in battery-backup mode. In battery-backup mode, current drain is less than 550nA.
The BQ3285LF write-protects the Clock calendar, and storage Registers during power failure. A backup battery then maintains data and operates the Clock and calendar.
The BQ3285LF 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.
The BQ3285LF is intended for use in 3V systems; however, it may also operate at 5V and then go into a 3V power-down state, write-protecting as if in a 3V system.
By Texas Instruments
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