DS1390U-33+T&R

Real Time Clock Overview

The DS1390U-33+T&R is a low-voltage serial peripheral interface (SPI) real-time clock/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 within a supply voltage range of 2.97V to 5.5V and supports an SPI clock frequency of up to 4MHz at 3.0V and 3.3V. It features a temperature-compensated voltage reference for power-fail detection and switching to a backup supply. The component is housed in a 10-pin µSOP package and is rated for operation over the industrial temperature range of -40°C to +85°C.

Real Time Clock Feature Summary

• 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 frequencies of 32.768kHz, 8.192kHz, 4.096kHz, or 1Hz
• One time-of-day alarm with maskable bits for tenths/hundredths of seconds, seconds, minutes, hours, day, and date
• Power-fail detect and switch circuitry automatically switches to backup supply when VCC falls below the power-fail threshold

Real Time Clock Applications

• Hand-Held Devices
• GPS/Telematics Devices
• Embedded Time Stamping
• Medical Devices

Real Time Clock Procurement Notes

Verify the specific ordering suffix '+T&R' corresponds to the tape-and-reel packaging format required for automated assembly processes. Confirm that the '-33' designation aligns with the target system's nominal 3.3V operating voltage requirements. Ensure the 10-pin µSOP footprint matches the printed circuit board layout specifications before finalizing procurement orders.

Real Time Clock Selection Notes

Select this component when an SPI interface is preferred over I2C or 3-wire alternatives within the DS139x family. The DS1390 variant specifically provides a single SQW/INT output pin, distinguishing it from models with separate interrupt pins or reset outputs. Verify that the system design can accommodate the external 32.768kHz quartz crystal with a 6pF load capacitance required for accurate timekeeping.

Real Time Clock Part Context

This part belongs to the DS1390–DS1394 series of low-voltage RTCs with trickle chargers. While the DS1391 replaces the SQW/INT pin with a reset function and the DS1392 uses a 3-wire interface, the DS1390 utilizes a standard 4-wire SPI bus. All devices in this series share similar core timekeeping capabilities and power management features but differ in pin configurations and interface protocols.

Real Time Clock Replacement Considerations

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