DS12885N+

Overview

The DS12885N+ is a real-time clock and calendar IC designed as a drop-in replacement for legacy IBM AT computer clocks. It provides timekeeping for seconds, minutes, hours, day, date, month, and year with automatic leap-year compensation through 2099. The device integrates 114 bytes of battery-backed static RAM and features a multiplexed byte-wide interface supporting both Intel and Motorola bus timing modes. It includes one time-of-day alarm, three maskable interrupts, and a programmable square-wave output. Primary power operates between 4.5V and 5.5V, while the backup supply accepts 2.5V to 4V. The component is housed in a 24-pin DIP package and supports industrial temperature ranges.

Feature Summary

• Multiplexed parallel interface compatible with Intel and Motorola bus protocols
• 114 bytes of nonvolatile battery-backed static RAM
• Automatic leap-year correction and daylight saving time options
• Programmable square-wave output and time-of-day alarm

Applications

• Embedded systems requiring precise timekeeping
• Utility meters for data logging
• Security systems with timestamp requirements
• Network hubs, bridges, and routers

Procurement Notes

Verify the specific suffix 'N+' indicates RoHS compliance when sourcing. Confirm the package type matches the required 24-DIP (0.600 inch) footprint. Ensure the design accommodates an external 32.768kHz crystal on pins X1 and X2, as this variant does not integrate the oscillator source internally unlike the DS12887 series.

Selection Notes

Select the DS12885N+ when a parallel interface is required for direct CPU connection without additional protocol controllers. Choose this part over the DS12C887 if a century byte is not needed, as the DS12885 lacks address 32h for century storage. Ensure the application can provide a stable 32.768kHz crystal with a 6pF load capacitance for accurate operation.

Part Context

The DS12885 family serves as a direct hardware replacement for the older DS1285 and DS1287 RTCs. While the DS12887 integrates a quartz crystal and lithium battery into the package, the DS12885 requires external components for these functions. This distinction makes the DS12885 suitable for designs where board space allows for discrete crystal and battery placement.

Replacement Considerations

The M48T86MH1E is listed as a substitute part number.