DS1390U-3+

Real Time Clock Overview

The DS1390U-3+ is a low-voltage real-time clock (RTC) 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 features an SPI-compatible bidirectional bus interface supporting Modes 1 and 3. It includes one programmable time-of-day alarm, power-fail detection with automatic switching to a backup supply, and trickle-charge capability for external batteries. The unit operates within a voltage range of 2.7V to 3.3V and is rated for industrial temperatures from -40°C to +85°C.

Real Time Clock Feature Summary

• SPI Interface: Supports Modes 1 and 3 with data rates up to 4MHz at 3.0V/3.3V.
• Timekeeping: Counts hundredths of seconds through year with leap-year correction.
• Power Management: Includes power-fail detect circuitry and automatic switch to VBACKUP.
• Alarm System: Features one programmable time-of-day/date alarm with interrupt generation.

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 'U-3+' against the manufacturer's current production status documentation. Confirm that the required SPI communication modes align with the host controller's capabilities, as this variant supports Modes 1 and 3. Ensure the system design accommodates the 2.7V to 3.3V operating voltage range and the 10-pin µSOP package dimensions.

Real Time Clock Selection Notes

Select the DS1390U-3+ when an SPI interface is preferred over I2C or 3-wire alternatives within the DS139x family. This model is suitable for applications requiring high-speed serial communication up to 4MHz. Designers must account for the specific SPI timing requirements and ensure the presence of an external 32.768kHz crystal with a 6pF load capacitance for accurate oscillator operation.

Real Time Clock Part Context

This component belongs to the DS1390–DS1394 series of low-voltage RTCs. While other models in the series utilize 3-wire interfaces or different SPI modes, the DS1390 specifically utilizes standard SPI Modes 1 and 3. The 'U' designation indicates the µSOP package, and the '-3+' suffix denotes the 3.0V nominal voltage variant with lead-free construction.

Real Time Clock Replacement Considerations

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