DS1339AU+

Real Time Clock Overview

The DS1339AU+ is a low-current, I2C 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 up to the year 2200. The device operates on a primary supply voltage (VCC) ranging from 1.71V to 5.5V and supports a backup supply (VBACKUP) between 1.3V and 3.7V. It features two programmable time-of-day alarms, a programmable square-wave output, and an automatic power-fail detect and switch circuitry that maintains timekeeping during power outages. The component is housed in an 8-pin µSOP package.

Real Time Clock Feature Summary

• I2C Serial Interface: Supports standard mode up to 400kHz for address and data transfer.
• Automatic Power-Fail Switching: Built-in circuit detects power failures and switches to VBACKUP without software intervention.
• Calendar and Clock: Counts seconds through year with leap-year correction; supports 12-hour and 24-hour formats.
• Trickle-Charger Capability: Internal circuit allows charging of backup batteries or super capacitors via selectable resistors.

Real Time Clock Applications

• Handheld devices such as GPS units and POS terminals
• Consumer electronics including set-top boxes and digital recorders
• Office equipment like fax machines, printers, and copiers
• Medical devices such as glucometers and medicine dispensers

Real Time Clock Procurement Notes

Verify the specific suffix 'AU+' against the manufacturer's current ordering guide to confirm package type and environmental compliance status. Confirm availability through authorized distributors as stock levels fluctuate. Ensure the selected variant matches the required voltage range and temperature specifications for the target application environment.

Real Time Clock Selection Notes

Select this RTC when a drop-in replacement for the DS1339 is required with extended calendar capabilities up to 2200. Ensure the system design accommodates the 32.768kHz external crystal requirements, specifically supporting crystals with up to 60kΩ ESR. Verify that the I2C bus pull-up voltages are compatible with the SDA and SCL pin limits relative to VCC.

Real Time Clock Part Context

The DS1339AU+ belongs to the Maxim Integrated DS1339A family of low-power serial real-time clocks. It serves as a direct functional upgrade to the earlier DS1339 model, adding century bit support and improved oscillator stability. The 'AU' designation typically indicates the µSOP-8 surface-mount package, while '+' denotes lead-free/RoHS compliance according to manufacturer standards.

Real Time Clock Replacement Considerations

The DS1339A is explicitly documented as a drop-in replacement for the DS1339. When substituting, verify that the legacy part's crystal load capacitance matches the DS1339A's 6pF requirement. Ensure that any previous software handling of the century bit is updated to accommodate the new register map at address 05h.