Datasheet AS1801 Ultra-Low Power, IC Serial Real-Time Clock with Trickle Charger 1 General Description 2 Key Features Real-Time Clock (RTC) counts seconds, minutes, hours, day, The AS1801 serial real-time clock is a low-power clock/calendar with date, month, and year with leap-year compensation valid up to two programmable time-of-day alarms and a programmable square- 2100 wave output. Address and data are transferred serially through an IC bus. 24-hour / 12-hour format with AM / PM indicator The clock/calendar provides seconds, minutes, hours, day, date, Trickle-Charger month, and year information. The date at the end of the month is IC Serial Interface automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or Two Time-of-Day alarms 12-hour format with AM / PM indicator. Oscillator Frequency Trimming (every 8 seconds, every 2 days) The AS1801 provides a clean clock/calendar start function by Oscillator Stop Flag (deep power down detection) clearing the wait for start flag in the control register. The flag is set whenever a clock/calendar setting takes place and the counter Wait-for-Start Flag for clean clock start operation is stopped until restarted by clearing the flag. Back-up counter allows long access times (>1s) of the serial In addition to the basic timekeeping functions the device offers dual interfaces power pins for primary and backup power supplies as well as a Programmable Square-Wave Output - Defaults to 1Hz on trickle charger at pin VBAT for the backup battery. Power-up The AS1801 provides two modes of frequency trimming for the Available in 8-pin TDFN (2x2mm) 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 -40C to +85C Operating temperature range both methods can be used simultaneously. A backup counter counts the seconds during read access to the 3 Applications clock/calendar registers and adds them after the end of the access The device is ideal for handhelds like GPS, POS Terminal, hence, making sure that date and time stay correct even if the Consumer Electronics like Set-Top Box, VCR/Digital Recording access takes longer than one second. 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. Figure 1. AS1801 - Typical Application Diagram & ( ) * + )( +% % Note: SCLK and SDA are open drain outputs, pull-up resistors are external www.austriamicrosystems.com/Real-Time-Clocks/AS1801 Revision 1.8 1 - 26AS1801 Datasheet - Pin Assignments 4 Pin Assignments Figure 2. Pin Assignments (Top View) 1 8 VCC X1 X2 2 7 VBAT AS1801 SCLK 3 6 SQW/INT SDA 4 5 GND 4.1 Pin Description Table 1. Pin Description Pin Name Pin Number Description Connections for a Standard 32.768kHz Quartz Crystal. The internal oscillator circuitry is X1 1 designed for operation with a crystal having a specified load capacitance (CL) of 6pF. An external 32.768kHz oscillator can also drive the AS1801. In this configuration, the X1 pin is X2 2 connected to the external oscillator signal and the X2 pin is floated. GND 5 Ground. DC power is provided to the device on this pin. Serial Clock Input. Open Drain Input. SCLK is used to synchronize data movement on the SCLK 3 IC interface. SDA 4 Serial Data Input/Output. Open drain digital I/O IC data pin. Square-Wave/Interrupt Output. Programmable Square-wave or Interrupt CMOS output signal. If the oscillator is running, SQW is running with 1Hz per default. SQW/INT 6 bit INTCN=0: SQW output bit INTCN=1: INT output Low-Power Operation in Single Supply and Battery-Operated Systems and Low-Power Battery Backup. In systems using the trickle charger, the rechargeable energy source is VBAT 7 connected to this pin. Supply Voltage. DC power is provided to the device on this pin. If VCC > VBAT: VCC is used VCC 8 to power the device. If VCC < VBAT: VBAT is used to power the device. Exposed Pad Not Connected. This pin is not connected may be left floating. www.austriamicrosystems.com/Real-Time-Clocks/AS1801 Revision 1.8 2 - 26