DS1339U-3+T&R

Real Time Clock Overview

The DS1339U-3+T&R is a low-power serial real-time clock (RTC) manufactured by Analog Devices Inc./Maxim Integrated. It provides seconds, minutes, hours, day, date, month, and year information with automatic leap-year compensation valid up to the year 2100. The device features two programmable time-of-day alarms and a programmable square-wave output accessible via an I2C serial interface. It includes a built-in power-fail detect circuit that automatically switches to a backup supply to maintain timekeeping. The component operates within a voltage range of 2.7V to 5.5V on VCC and supports an operating temperature range of -40°C to +85°C.

Real Time Clock Feature Summary

• I2C Serial Interface for communication with microcontrollers
• Automatic Power-Fail Detect and Switch Circuitry
• Two Programmable Time-of-Day Alarms
• Programmable Square-Wave Output (1Hz, 4.096kHz, 8.192kHz, 32.768kHz)
• Trickle-Charge Capability for battery or super capacitor maintenance

Real Time Clock Applications

• Handhelds (GPS, POS Terminals)
• Consumer Electronics (Set-Top Box, Digital Recording, Network Appliance)
• Office Equipment (Fax/Printers, Copier)
• Medical Devices (Glucometer, Medicine Dispenser)
• Telecommunications (Routers, Switches, Servers)

Real Time Clock Procurement Notes

Verify the specific ordering suffix '+T&R' corresponds to the tape-and-reel packaging format as indicated in distributor listings. Confirm the 'U-3' designation aligns with the required 3.0V nominal supply voltage specifications. Ensure compliance with RoHS requirements associated with the '+' suffix. Cross-reference the manufacturer part number with official Analog Devices documentation to confirm availability status and lead times prior to procurement.

Real Time Clock Selection Notes

Select this component when a low-power RTC with I2C interface and automatic power failover is required. The 'U-3' variant is suitable for systems with a 3.0V nominal supply voltage, operating between 2.7V and 5.5V. Consider the integrated trickle charger if direct battery charging from the main supply is needed. Ensure the application requires the 8-pin µSOP package form factor and operates within the -40°C to +85°C temperature range.

Real Time Clock Part Context

The DS1339 series includes variants such as DS1339C with an integrated crystal and other voltage options like DS1339U-2+ (2.0V) and DS1339U-33+ (3.3V). The DS1339U-3+T&R specifically denotes the 3.0V version in an 8-pin µSOP package supplied in a tape-and-reel format. It serves as a drop-in replacement for older Dallas Semiconductor RTC designs while offering modern I2C compatibility and UL recognition.

Real Time Clock Replacement Considerations

DS1339U-33+T&R

Real Time Clock FAQ

How does the DS1339 handle power failures?

The DS1339 has a built-in power-sense circuit that detects when VCC falls below the power-fail threshold (VPF). It automatically switches to the backup supply connected to the VBACKUP pin, maintaining time, date, and alarm operation without interruption.

What is the function of the Trickle Charger Register?

The Trickle Charger Register allows the DS1339 to charge a backup source, such as a lithium cell or super capacitor, directly from the VCC supply. Users can configure diode selection and resistor values (250Ω, 2kΩ, or 4kΩ) to control the charging current.

Can the DS1339 operate in both 12-hour and 24-hour formats?

Yes, the clock operates in either the 24-hour or 12-hour format with an AM/PM indicator. The mode is selected via bit 6 of the hours register. In 12-hour mode, bit 5 indicates AM or PM.