DS1685-3+

Real Time Clock Overview

The DS1685-3+ is a 3V real-time clock (RTC) manufactured by Analog Devices Inc./Maxim Integrated. It operates within a temperature range of 0°C to +70°C and utilizes a multiplexed address/data bus interface. The device provides timekeeping with a calendar valid through 2099, including leap-year compensation. It features 242 bytes of battery-backed nonvolatile RAM and incorporates a 64-bit silicon serial number. Power control circuitry supports system power-on via date/time alarms or key closures.

Real Time Clock Feature Summary

• Incorporates industry-standard DS1287 PC clock functions with Y2K compliance and leap-year compensation valid through 2099.
• Provides 242 bytes of user-accessible nonvolatile SRAM divided into two memory banks for data retention during power loss.
• Features power-control circuitry allowing system wake-up from date/time alarms or kickstart inputs via the PWR output pin.
• Includes a 32kHz square-wave output and a crystal-select bit for compatibility with 6pF or 12.5pF load capacitance crystals.

Real Time Clock Applications

• Embedded systems requiring precise timekeeping and nonvolatile storage.
• Utility meters needing reliable clock/calendar functionality.
• Security systems utilizing alarm-based wake-up capabilities.
• Network hubs, bridges, and routers requiring RTC synchronization.

Real Time Clock Procurement Notes

Verify component authenticity through official manufacturer channels or authorized distributors. Confirm RoHS compliance status as indicated by the '+' suffix in the part number. Ensure the operating voltage matches the specific 3V variant requirements for the target application design.

Real Time Clock Selection Notes

Select the DS1685-3+ when a 3V supply is available and an industrial temperature range is not required. Choose this PDIP package version for through-hole mounting applications. Consider alternative packages like TSSOP or PLCC if space constraints or surface-mount technology are necessary for the PCB layout.

Real Time Clock Part Context

The DS1685-3+ belongs to the DS1685/DS1687 family of 3V/5V Real-Time Clocks. It serves as a successor to earlier industry-standard PC RTCs such as the DS1285 and DS1385. The device integrates enhanced features like a silicon serial number and auxiliary battery input support while maintaining backward compatibility with existing BIOS implementations.

Real Time Clock Replacement Considerations

The DS1685-5+ is a direct replacement offering identical functionality but designed for 5V operation. For extended temperature ranges, the DS1685E-3+ (TSSOP) or DS1685EN-3+ variants provide similar features with industrial grade specifications.