DS1339C-33

Real Time Clock Overview

The DS1339C-33 is a low-power I2C serial real-time clock (RTC) from Analog Devices/Maxim Integrated, housed in a 16-pin SOIC package with an integrated 32.768kHz crystal. It provides seconds, minutes, hours, day, date, month, and year information with automatic leap-year compensation valid up to the year 2100. The device operates on a primary supply voltage range of 2.97V to 5.5V and supports a backup supply between 1.3V and 3.7V. Key features include two programmable time-of-day alarms, a programmable square-wave output, and an oscillator stop flag. An internal power-fail detect circuit automatically switches to the backup supply to maintain timekeeping during main power loss.

Real Time Clock Feature Summary

• I2C Serial Interface: Supports standard (100kHz) and fast mode (400kHz) communication protocols for address and data transfer.
• Integrated Crystal: Includes a built-in 32.768kHz quartz crystal, eliminating the need for external oscillator components.
• Automatic Power Switching: Built-in power-sense circuit detects failures and switches to VBACKUP to preserve time and alarm data.
• Leap-Year Compensation: Automatically adjusts for months with fewer than 31 days and leap years through 2100.

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
• Telecommunications infrastructure including routers, switches, and servers

Real Time Clock Procurement Notes

Verify that the specific part number corresponds to the 16-pin SOIC package variant with the integrated crystal. Confirm the operating voltage requirement matches the system's 3.3V rail, as indicated by the '-33' suffix. Ensure compatibility with the I2C bus voltage levels and check for RoHS compliance status if required by assembly specifications.

Real Time Clock Selection Notes

Select this component when a compact RTC solution with an integrated crystal is required to save board space. It is suitable for applications needing dual alarms and trickle-charging capabilities for backup batteries or supercapacitors. Consider the 16-pin SOIC footprint constraints and ensure the design accommodates the necessary pull-up resistors for the SDA and SQW/INT lines.

Real Time Clock Part Context

The DS1339C-33 belongs to the DS1339 family of real-time clocks. The 'C' designation specifically indicates the version with an integrated crystal, distinguishing it from the DS1339U which requires an external crystal. This family offers drop-in replacement capabilities for older Dallas Semiconductor RTCs while providing enhanced features like improved accuracy and additional alarm configurations.

Real Time Clock Replacement Considerations

The datasheet identifies the DS1339A as a drop-in replacement for the DS1339. Verify pinout compatibility and register mapping before substituting. Other variants within the DS1339 series may differ in package type or crystal integration requirements.

Real Time Clock FAQ

["What is the function of the integrated crystal in the DS1339C?","The DS1339C includes a standard 32,768Hz crystal within the package, removing the need for external oscillator components and simplifying PCB layout."]

["How does the device handle power failures?","The DS1339C features a built-in power-sense circuit that monitors VCC. If VCC drops below the power-fail threshold (VPF), the device automatically switches to the VBACKUP supply to maintain timekeeping and alarm operations."]

["What are the available square-wave output frequencies?","The programmable square-wave output can be configured to 1Hz, 4.096kHz, 8.192kHz, or 32.768kHz via the Rate Select bits in the Control Register."]