DS1391U-33+T&R

Real Time Clock Overview

The DS1391U-33+T&R is a low-voltage real-time clock (RTC) from Analog Devices/Maxim Integrated, operating within a supply voltage range of 2.97V to 5.5V. It features an SPI-compatible bidirectional bus interface supporting Modes 1 and 3 at frequencies up to 4MHz. The device provides timekeeping for hundredths of seconds through year, with automatic leap-year compensation valid until 2100. Key functional blocks include a programmable time-of-day alarm, power-fail detection circuitry, and trickle-charging capability for backup sources. It utilizes a 10-pin µSOP package and operates across the industrial temperature range of -40°C to +85°C.

Real Time Clock Feature Summary

• SPI Interface: Supports Modes 1 and 3 with SCLK frequencies up to 4MHz at 3.0V/3.3V.
• Timekeeping: Counts hundredths of seconds, seconds, minutes, hours, day, date, month, and year with BCD format.
• Power Management: Includes power-fail detect and switch circuitry; supports trickle charging via selectable resistors.
• Reset Functionality: Features an RST output/debounced input pin for pushbutton reset requests.

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 tape-and-reel packaging when sourcing components. Confirm that the '-33' designation aligns with the required 2.97V to 5.5V supply voltage range for the target application. Ensure compatibility with SPI Modes 1 and 3 for system integration.

Real Time Clock Selection Notes

Select this component if an SPI interface is preferred over I2C or 3-wire alternatives within the DS139x family. The DS1391 variant is distinct due to its RST pin configuration, replacing the SQW/INT pin found in other models like the DS1390. Verify that the 10-pin µSOP package fits the PCB layout constraints.

Real Time Clock Part Context

This part belongs to the DS1390–DS1394 series of low-voltage RTCs. While sharing core timekeeping and power management features, the DS1391 is specifically differentiated by its RST output/debounced input pin instead of a square-wave/interrupt output. It shares the same package and electrical characteristics as the DS1390 and DS1394.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. Consider verifying availability of the base model DS1391U-33+ or checking for end-of-life notices from the manufacturer.