DS1685-5+

Real Time Clock Overview

The DS1685-5+ is a real-time clock (RTC) designed for +5V operation within the Analog Devices/Maxim Integrated DS1685 family. It provides timekeeping and calendar functions with leap-year compensation valid through 2099, alongside 242 bytes of battery-backed nonvolatile RAM. The device features a multiplexed address/data bus interface and includes enhanced capabilities such as a 64-bit silicon serial number, power-control circuitry for system wake-up, and a 32kHz square-wave output. It operates within a commercial temperature range of 0°C to +70°C and is housed in a 24-pin PDIP package.

Real Time Clock Feature Summary

• Integrated 242-byte battery-backed NV SRAM divided into two banks for user data storage
• +5V primary supply operation with automatic switching to backup battery when VCC drops below the power-fail trip point
• Power-on control via external kickstart input or programmable date/time alarm
• Y2K compliant timekeeping algorithm with century register and daylight savings adjustment support

Real Time Clock Applications

• Embedded systems requiring persistent timekeeping
• Utility meters needing accurate logging intervals
• Security systems with event timestamping
• Network hubs, bridges, and routers for protocol synchronization

Real Time Clock Procurement Notes

Verify that the specific application requires the +5V voltage variant, as the DS1685 series also offers a +3V version. Confirm the 24-pin PDIP package meets the target PCB footprint requirements. Ensure the design accounts for the commercial temperature range limits of 0°C to +70°C during component selection.

Real Time Clock Selection Notes

Select this component when a standard PC-compatible RTC interface is required alongside substantial nonvolatile memory. The multiplexed bus architecture allows direct connection to standard microprocessors without additional demultiplexing logic. Consider the DS1687 if an integrated crystal and battery solution is preferred over discrete components.

Real Time Clock Part Context

The DS1685-5+ serves as a successor to industry-standard DS1285 and DS1385 RTCs, offering backward compatibility with existing BIOS implementations while adding modern enhancements. It belongs to the DS1685/DS1687 family, which distinguishes itself through the inclusion of extended user RAM and dedicated power-management outputs not found in earlier generations.

Real Time Clock Replacement Considerations

Direct pin-compatible replacements include other members of the DS1685 family, such as the DS1685E-5+ for surface-mount applications or the DS1685S-5+ for SO packages. Verify that any substitute maintains the same +5V operating voltage and multiplexed bus timing characteristics.