説明

The AS1801 serial real-time clock is a low-power clock/calendar with two programmable time-of-day alarms and a programmable square-wave output. Address and data are transferred serially through an I²C bus. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator.

The AS1801 provides a clean clock/calendar start function by clearing the ‘wait_for_start’ flag in the control register. The flag is set whenever a clock/calendar setting takes place and the counter operation is stopped until restarted by clearing the flag. In addition to the basic timekeeping functions the device offers dual power pins for primary and backup power supplies as well as a trickle charger at pin VBAT for the backup battery.

The AS1801 provides two modes of frequency trimming for the external quartz crystal in steps of 3.81 ppm within an 8-second interval and in steps 5.8 ppm within a 2-day period. None, one or both methods can be used simultaneously. A backup counter counts the seconds during read access to the clock/calendar registers and adds them after the end of the access hence, making sure that date and time stay correct even if the access takes longer than one second

主な機能

• Real-Time Clock (RTC) Counts Seconds, Minutes, Hours, Day, Date, Month, and Year with Leap-Year Compensation Valid Up to 2100
• 24-hour / 12-hour format with AM/PM Indicator
• Trickle-Charger
• I²C Serial Interface
• Two Time-of-Day Alarms
• Oscillator Frequency Trimming (every 8 seconds, every 2 days)
• Oscillator Stop Flag (deep power down detection)
• Wait-for-Start Flag for clean clock start
• Back-up counter allows long access times (>1s) of the serial interfaces
• Programmable Square-Wave Output - Defaults to 1Hz on Power-up
• Available in 8-Pin TDFN 2x2mm
• -40ºC to +85ºC Operating Temperature Range

ｱﾌﾟﾘｹｰｼｮﾝ

The device is ideal for handhelds like GPS, POS Terminal, Consumer Electronics like Set-Top Box, VCR/ Digital Recording; Office Equipment such as Fax/Printer, Copier; Medical implements such as Glucometer, Medicine Dispenser; Telecommunications like Router, Switch, Server; and many other applications like Utility Meters, Vending Machines, Thermostats and Modems.

Block diagram for AS1801 Real Time Clock