General Description

    The low-voltage serial-peripheral interface (SPI™) AT1390/AT1391/AT1394 and the low-voltage 3-wire AT1392/AT1393 real-time clocks (RTCs) are clocks/cal-endars that provide hundredths of a second, 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 an AM/PM indicator. One programmable time-of-day alarm is provided. A temperature-compensated voltage reference monitors the status of V_CC and automatically disables the bus interface and switches to the backup supply if a power failure is detected. On the AT1390, a single open-drain output provides a CPU interrupt or a square wave at one of four selectable frequencies. The AT1391 replaces the SQW/INT pin with a RST output/ debounced input.

    The AT1390, AT1391, and AT1394 are programmed serially through an SPI-compatible, bidirectional bus. The AT1392 and AT1393 communicate over a 3-wire serial bus, and the extra pin is used for either a sepa-rate interrupt pin or a RST output/debounced input.

     All five devices are available in a 10-pin µSOP package, and are rated over the industrial temperature range.

Applications

• Hand-Held Devices 

• GPS/Telematics Devices 

• Embedded Time Stamping 

• Medical Devices

Features

• Real-Time Clock Counts Hundredths of Seconds, Seconds, Minutes, Hours, Day, Date, Month, and Year with Leap-Year Compensation Valid Up to 2100

• Output Pin Configurable as Interrupt or Square Wave with Programmable Frequency of 32.768kHz, 8.192kHz, 4.096kHz, or 1Hz (AT1390/AT1393/AT1394 Only)

• One Time-of-Day Alarm

• Power-Fail Detect and Switch Circuitry

• Reset Output/Debounced Input (AT1391/AT1393) 

• Separate SQW and INT Output (AT1392)

• Trickle-Charge Capability

• SPI Supports Modes 0 and 2 (AT1394)

• SPI Supports Modes 1 and 3 (AT1390/AT1391)

• 3-Wire Interface (AT1392/AT1393)

• 4MHz at 3.0V and 3.3V

• 1MHz at 1.8V

• Three Operating Voltages: 1.8V ±5%, 3.0V ±10%,and 2.97 to 5.5V (AT1394:3.3V ±10%)

• Industrial Temperature Range: -40℃ to +85℃ 

• Underwriters Laboratories (UL) Recognized

•