BQ3285LFSS-A1TR

Overview

The BQ3285LFSS-A1TR is a low-power CMOS real-time clock (RTC) and calendar integrated circuit manufactured by Texas Instruments. It provides time-of-day tracking with a 100-year calendar, alarm features, and 242 bytes of general nonvolatile storage. The device operates on a 2.7V to 3.6V supply voltage and supports parallel bus interfaces compatible with Intel or Motorola architectures. Key specifications include a battery backup current of less than 0.5µA, a 32.768kHz output for power management, and selectable square-wave frequencies. It functions within a commercial temperature range of 0°C to 70°C and is housed in a 24-pin SSOP package.

Feature Summary

• Direct replacement for IBM AT-compatible computers with DS1285 functionality
• 242 bytes of general nonvolatile SRAM storage
• Three individually maskable interrupt sources: periodic, alarm, and update-ended
• Battery-backed operation with less than 0.5µA load under battery conditions

Applications

• IBM AT-compatible computer systems
• Microprocessor peripheral timekeeping
• System wake-up via alarm interrupt in battery-backup mode

Procurement Notes

Verify the 'TR' suffix indicates tape-and-reel packaging if required by assembly equipment. Confirm the 'L' designation matches the 2.7V–3.6V operating voltage requirement. Check for end-of-life status as the base model has been discontinued; ensure availability through authorized distributors or secondary markets.

Selection Notes

Select this component when a parallel interface RTC with significant nonvolatile storage is needed. Ensure the system voltage aligns with the bq3285L range (2.7V–3.6V). Verify that the host processor can support the multiplexed address/data bus timing for either Intel or Motorola modes. Consider the 24-SSOP package constraints for PCB layout.

Part Context

This part belongs to the bq3285E/L family from Texas Instruments. The 'LFSS' indicates a lead-free, plastic SSOP package variant. The 'A1' suffix typically denotes a specific revision or manufacturing lot code. The 'TR' suffix specifies tape-and-reel packaging for automated placement.

Replacement Considerations

Functionally compatible with the Dallas Semiconductor DS1285 and closely matches MC146818A pin configurations. Direct substitutes may require verification of voltage levels and bus timing compatibility.