DS12885SN+T&R

Overview

The DS12885SN+T&R is a real-time clock (RTC) and calendar IC in a 24-SOIC surface-mount package. It provides timekeeping for seconds, minutes, hours, day, date, month, and year with leap-year compensation through 2099. The device includes 114 bytes of battery-backed static RAM and supports both Intel and Motorola multiplexed bus interfaces. Primary power operates between 4.5V and 5.5V, while the backup supply accepts 2.5V to 4V. It features an automatic power-fail detection circuit that switches to the backup source. The industrial temperature range spans from -40°C to +85°C.

Feature Summary

• Multiplexed byte-wide interface supporting selectable Intel or Motorola bus timing modes
• 114 bytes of nonvolatile, battery-backed static RAM with RAM clear function
• Automatic power-fail detect and switch circuitry for continuous operation during primary power loss
• 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 package designation matches the 24-SOIC form factor and confirm the tape-and-reel packaging configuration. Ensure the operating environment falls within the specified -40°C to +85°C industrial temperature range. Check that the system design accommodates the required 4.5V to 5.5V primary supply voltage and appropriate battery backup connections.

Selection Notes

Select this component when a drop-in replacement for legacy IBM AT clock/calendar designs is required. Choose the DS12885 over the DS12C887 if a century byte at address 32h is not needed, as the DS12885 utilizes that address for general-purpose RAM. Ensure the application can support the external 32.768kHz crystal oscillator requirements and layout constraints.

Part Context

This part belongs to the DS12885 family, which serves as a direct successor to the DS1285 and DS1287. The family includes variants like the DS12887, which integrates a quartz crystal and lithium energy source into a single encapsulated DIP package. The DS12885SN+T&R specifically denotes the standard commercial/industrial version without integrated energy sources, supplied in a reel format.

Replacement Considerations

The DS12885 is designed as a direct pin-compatible replacement for the Dallas Semiconductor DS1285 and DS1287. When substituting older parts, verify that the existing board layout supports the 24-SOIC package dimensions and that the external crystal parameters meet the specified load capacitance requirements.