DS12885S+T&R

Overview

The DS12885S+T&R is a real-time clock (RTC) and calendar integrated circuit manufactured by Analog Devices Inc./Maxim Integrated. It provides timekeeping for seconds, minutes, hours, day, date, month, and year with automatic leap-year compensation through 2099. The device includes 114 bytes of battery-backed static RAM and supports both Intel and Motorola multiplexed bus interfaces. It operates on a primary supply of 4.5V to 5.5V and switches automatically to a backup supply upon power failure. The component is housed in a 24-SOIC package and functions within a commercial temperature range of 0°C to +70°C.

Feature Summary

• Multiplexed byte-wide interface supporting selectable Intel or Motorola bus timing modes
• 114 bytes of general-purpose, battery-backed nonvolatile static RAM
• Automatic power-fail detection and switching circuitry between VCC and VBAT supplies
• Programmable square-wave output and time-of-day alarm with maskable interrupts

Applications

• Embedded systems requiring precise timekeeping
• Utility meters for data logging and billing cycles
• Security systems needing event timestamping
• Network hubs, bridges, and routers for synchronization

Procurement Notes

Verify the specific ordering suffix against manufacturer documentation to confirm packaging type and temperature grade. The 'T&R' designation indicates Tape and Reel packaging. Confirm that the commercial temperature range (0°C to +70°C) meets the operational requirements of the target environment. Ensure compatibility with the system's voltage levels and bus timing mode before integration.

Selection Notes

Select this component when a drop-in replacement for IBM AT computer clock/calendar functionality is required. It is suitable for designs utilizing parallel interfaces rather than serial protocols like I2C or SPI. Consider the 114-byte RAM capacity for application-specific data storage needs. Verify that the external 32.768kHz crystal selection aligns with the oscillator load capacitance specifications to ensure accurate timekeeping.

Part Context

The DS12885 family is designed as a direct replacement for the legacy DS1285 and DS1287 RTCs. The DS12885 variant specifically utilizes an external quartz crystal and battery connection, unlike the DS12887 which integrates these components in an EDIP package. This model belongs to the broader Maxim Integrated RTC portfolio known for high reliability and long-term data retention capabilities.

Replacement Considerations

Public confirmed substitute part numbers: DS12885SN+, DS12885Q+.