DS12885Q+

Overview

The DS12885Q+ is a real-time clock and calendar IC manufactured by Analog Devices Inc./Maxim Integrated. It serves as a direct replacement for legacy devices like the DS1285, featuring a multiplexed parallel interface in a 28-PLCC package. The device provides 114 bytes of battery-backed static RAM and tracks seconds, minutes, hours, days, dates, months, and years with leap-year compensation valid through 2100. It supports both 12-hour and 24-hour time formats with AM/PM indication. Primary power operates between 4.5V and 5.5V, while battery backup ranges from 2.5V to 4V. Maximum timekeeping current is 15mA at 4.5V–5.5V, operating within a commercial temperature range of 0°C to 70°C.

Feature Summary

• Integrated 114-byte NVSRAM accessible via AD6 logic level
• Hardware leap-year compensation valid up to the year 2100
• Programmable square-wave output and three maskable interrupts
• Daylight Savings Time option and selectable bus timing

Applications

• IBM AT computer clock/calendar systems
• Industrial data logging equipment requiring persistent timekeeping
• Embedded systems needing hardware-based calendar management

Procurement Notes

Verify RoHS compliance status directly with the manufacturer or authorized distributors, as historical records indicate potential variations between leaded and lead-free versions of this component family. Confirm availability as production status may vary across different manufacturing lots or regional supply chains. Ensure the specific ordering suffix matches the required package and environmental specifications for your design.

Selection Notes

Select the DS12885Q+ when a drop-in replacement for the DS1285 is required with additional general-purpose RAM storage. This part is suitable for designs utilizing multiplexed parallel buses where pin efficiency is critical. Consider the 28-PLCC surface-mount package for compact PCB layouts. Verify that the system voltage aligns with the 4.5V–5.5V supply range and that the 0°C to 70°C operating temperature meets environmental requirements.

Part Context

The DS12885 series belongs to the Dallas Semiconductor (now Maxim Integrated/Analog Devices) RTC family, designed to replace older MC146818B and DS1285 components. The 'Q' suffix denotes the 28-pin PLCC package variant, while the '+' indicates RoHS-compliant construction. This component integrates the clock functionality with non-volatile memory to maintain system time during primary power failures using a lithium coin-cell backup source.

Replacement Considerations

The DS12885T is listed as a direct replacement alternative with a 32-TQFP package. Designers transitioning from the DS1285 should verify pin compatibility, noting that the DS12885 adds RAM access control via AD6.