DS1390U-3+T&R

Real Time Clock Overview

The DS1390U-3+T&R is a low-voltage serial peripheral interface (SPI) real-time clock and calendar manufactured by Analog Devices Inc./Maxim Integrated. It provides hundredths of a second, seconds, minutes, hours, day, date, month, and year information with automatic leap-year compensation valid up to the year 2100. The device operates on a single supply voltage ranging from 2.7V to 3.3V and supports an industrial temperature range of -40°C to +85°C. It features a programmable time-of-day alarm, power-fail detection circuitry that automatically switches to a backup supply, and trickle-charging capability for external batteries.

Real Time Clock Feature Summary

• SPI-compatible bidirectional bus interface supporting Modes 1 and 3 at frequencies up to 1MHz at 1.8V or 4MHz at 3.0V/3.3V
• Real-time clock counts hundredths of seconds through year with leap-year compensation valid until 2100
• Power-fail detect and switch circuitry with temperature-compensated voltage reference monitoring VCC status
• Trickle-charge capability with selectable current-limiting resistors for battery maintenance

Real Time Clock Applications

• Hand-held devices requiring precise timekeeping
• GPS and telematics systems for embedded time stamping
• Medical devices needing reliable calendar functions
• Embedded systems utilizing SPI communication protocols

Real Time Clock Procurement Notes

Verify the specific ordering suffix '+T&R' corresponds to the tape-and-reel packaging format when sourcing components. Confirm that the '-3' designation aligns with the required 2.7V to 3.3V operating voltage range for your system design. Ensure compatibility with the 10-pin µSOP package dimensions during PCB layout planning.

Real Time Clock Selection Notes

Select this component if the application requires an SPI interface rather than I2C or 3-wire alternatives within the DS139x family. The DS1390 variant specifically provides an open-drain SQW/INT output pin, distinguishing it from the RST-focused DS1391. Consider the 10-pin µSOP footprint constraints and verify that the 2.7V minimum supply voltage meets the system's power budget requirements.

Real Time Clock Part Context

This part belongs to the DS1390–DS1394 series of low-voltage RTCs. While the DS1391 replaces the interrupt pin with a reset function and the DS1392/DS1393 utilize a 3-wire interface, the DS1390 maintains the standard SPI configuration with dedicated data input/output lines and a configurable square wave/interrupt output.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation.