DS17485E-5

Real Time Clock Overview

The DS17485E-5 is a real-time clock (RTC) IC designed as a successor to the industry-standard DS12885 and DS12887. It provides timekeeping for seconds, minutes, hours, day, date, month, and year with leap-year compensation through 2099. The device features a multiplexed byte-wide interface, one time-of-day alarm, three maskable interrupts, and a programmable square-wave output. It includes 114 bytes of general-purpose battery-backed NV SRAM plus 4096 bytes of extended battery-backed NV SRAM. Operating at +5.0V nominal, it supports automatic power-fail detection and switching to a backup supply.

Real Time Clock Feature Summary

• Incorporates industry-standard DS12887 PC clock functions plus enhanced features like a 64-bit silicon serial number and SMI recovery stack.
• Provides 4096 bytes of extended battery-backed NV SRAM in addition to 114 bytes of general-purpose user RAM.
• Features power-control circuitry that allows system power-on via external stimulus or time-and-date wake-up alarm.
• Includes automatic power-fail detect and switch circuitry to maintain operation on backup supply when primary power is lost.

Real Time Clock Applications

• Embedded Systems
• Utility Meters
• Security Systems
• Network Hubs, Bridges, and Routers

Real Time Clock Procurement Notes

Verify component authenticity by checking the manufacturer marking against the official datasheet specifications. Confirm the ordering suffix matches the required voltage range (+5V operation). Ensure the package type corresponds to the specific variant ordered, as pinouts may vary across the DS17x85 family.

Real Time Clock Selection Notes

Select this part for applications requiring a direct replacement for legacy DS12885/DS12887 designs with added nonvolatile memory. Choose the +5V version for systems operating within the 4.5V to 5.5V supply range. Consider the DS17487 if an integrated crystal and battery solution is preferred over discrete components.

Real Time Clock Part Context

The DS17485 belongs to the DS17x85 family of real-time clocks from Analog Devices / Maxim Integrated. This series serves as modern successors to the Dallas Semiconductor DS12885 and DS12887 standards, offering improved features such as extended NV SRAM and power control logic while maintaining compatibility with existing BIOS implementations.

Real Time Clock Replacement Considerations

Direct substitutes include other members of the DS17x85 family, such as the DS17285 (2KB extended RAM) or DS17885 (8KB extended RAM), provided the memory requirements align. For standalone modules with integrated battery and crystal, consider the DS17487.