DS12885T+

Overview

The DS12885T+ is a real-time clock (RTC) and calendar integrated circuit manufactured by Analog Devices Inc./Maxim Integrated. It serves as a drop-in replacement for legacy IBM AT computer clocks, providing timekeeping for seconds, minutes, hours, day, date, month, and year with leap year compensation through 2099. The device features 114 bytes of battery-backed static RAM and supports both Intel and Motorola bus timing modes via a multiplexed parallel interface. It operates within a supply voltage range of 4.5V to 5.5V, drawing a maximum current of 15mA during active operation. The component is housed in a 32-TQFP surface-mount package and functions reliably across a commercial temperature range of 0°C to 70°C.

Feature Summary

• Integrated RTC/Calendar with Leap Year Compensation through 2099
• 114 Bytes of Battery-Backed Static RAM
• Multiplexed Parallel Interface Supporting Intel and Motorola Modes
• Automatic Power-Fail Detection and Switching Circuitry

Applications

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

Procurement Notes

Verify the specific ordering suffix 'T+' against the manufacturer's datasheet to confirm the package type and environmental compliance status. Confirm that the required operating temperature range aligns with the commercial specification (0°C to 70°C). Ensure the primary power supply remains stable between 4.5V and 5.5V to prevent unintended switching to backup power. Check for availability of compatible lithium coin-cell batteries for the VBAT input if long-term data retention is required during power outages.

Selection Notes

Select the DS12885T+ when a direct parallel interface replacement for older IBM AT systems is required. This model is suitable for applications needing nonvolatile memory alongside timekeeping functions. Consider the 32-TQFP package constraints for PCB layout. If industrial temperature ranges (-40°C to +85°C) are necessary, verify if an alternative variant from the same family is available, as this specific part number specifies commercial grade limits.

Part Context

The DS12885T+ belongs to the DS12885 family of real-time clocks, which also includes variants like the DS12887 and DS12C887A. These devices share core functionalities such as the RTC engine and RAM architecture but differ in packaging and additional features like integrated crystals or century bytes. The T+ suffix indicates the 32-pin Thin Quad Flat Package (TQFP) configuration, distinguishing it from DIP or PLCC options found in other family members.

Replacement Considerations

The DS12885T+ is designed as a direct pin-compatible replacement for the DS1285 and DS1287. When substituting older components, ensure the host system supports the multiplexed address/data bus timing. Verify that the external 32.768kHz crystal meets the specified load capacitance requirements to maintain accuracy.