DS14285

Real Time Clock Overview

The DS14285 is a Real-Time Clock (RTC) with Non-Volatile Static RAM, designed as a direct replacement for the IBM AT computer clock. It provides timekeeping for seconds, minutes, hours, days, dates, months, and years with leap year compensation valid through 2100. The device features a multiplexed address/data bus interface compatible with Intel or Motorola timing protocols. It includes 114 bytes of general-purpose nonvolatile RAM and 14 bytes of control registers. The DS14285 operates on a +5V supply with automatic switching to a backup battery source during power failures.

Real Time Clock Feature Summary

• Direct replacement for IBM AT clock/calendar with functionally compatible interface to DS1285/DS1287
• Multiplexed bus interface supporting both Intel and Motorola timing modes via MOT pin
• Automatic write protection and external SRAM nonvolatility control using VCCO and CEO pins
• Programmable square wave output and three software-maskable interrupt sources

Real Time Clock Applications

• IBM AT compatible computer systems
• Industrial controllers requiring real-time tracking
• Embedded systems needing nonvolatile data retention during power loss

Real Time Clock Procurement Notes

Verify component status as the DS14285 series may be discontinued. Confirm package type availability (DIP, SOIC, PLCC) and temperature grade (commercial or industrial). Ensure ordering suffixes match required specifications, such as lead-free compliance (+) or tape and reel packaging (/T&R). Check for functional equivalents if original parts are unavailable.

Real Time Clock Selection Notes

Select the appropriate package variant based on board layout: DS14285 for DIP, DS14285S for SOIC, or DS14285Q for PLCC. Choose industrial temperature grades (suffix N) for environments outside 0°C to +70°C. For standalone operation without external crystals or batteries, consider the DS14287 module. Ensure external SRAM selection matches the voltage and current requirements supported by the VCCO output.

Real Time Clock Part Context

The DS14285 belongs to the Dallas Semiconductor RTC family, succeeding earlier models like the DS1285. It integrates clock/calendar functions with nonvolatile memory management. The device distinguishes itself from the DS14287 by requiring external components for the crystal oscillator and backup power source, whereas the DS14287 encapsulates these internally.

Real Time Clock Replacement Considerations

The DS1685S-5+ is listed as a similar available substitute. Verify pin compatibility and register mapping before substitution. Ensure the replacement supports the required bus timing mode and voltage levels.