BQ3285LFSS-A1TRG4

Overview

The BQ3285LFSS-A1TRG4 is a low-power CMOS real-time clock (RTC) and calendar IC from Texas Instruments, designed as a direct replacement for IBM AT-compatible systems. It operates on a 2.7V to 3.6V supply with battery backup support via the BC pin. The device provides 242 bytes of general nonvolatile storage and features a multiplexed parallel interface compatible with Intel or Motorola bus timing. Key specifications include a 32.768kHz output, programmable square wave, and three maskable interrupt sources. It supports BCD or binary time formats, automatic leap-year adjustment, and daylight saving time adjustments within a commercial temperature range of 0°C to 70°C.

Feature Summary

• Direct replacement for DS1285/MC146818A with functionally compatible pin configuration
• 242 bytes of general nonvolatile SRAM storage accessible via parallel interface
• Low power consumption with less than 0.5μA load under battery operation
• System wake-up capability through alarm interrupt active in battery-backup mode

Applications

• IBM AT-compatible computers and legacy PC architectures
• Industrial control systems requiring precise timekeeping
• Battery-backed data logging applications
• Embedded systems needing periodic or alarm-based interrupts

Procurement Notes

Verify component authenticity and check for end-of-life status, as this part may be discontinued by the manufacturer. Confirm that the TRG4 suffix indicates tape-and-reel packaging suitable for automated assembly processes. Ensure compatibility with existing PCB footprints and voltage levels before procurement.

Selection Notes

Select the bq3285L variant specifically for 3V system designs, as it differs from the 5V bq3285E. Ensure the design includes an external 32.768kHz crystal with 6pF load capacitance. Verify that the host processor can handle the multiplexed address/data bus timing requirements for either Intel or Motorola modes.

Part Context

This component belongs to the bq3285 family of real-time clocks. The LFSS-A1 designation identifies the specific lead-free SSOP package variant. It serves as a peripheral for microprocessors, providing time-of-day, calendar, and alarm functions without requiring complex external logic.

Replacement Considerations

Functionally compatible with the Dallas Semiconductor DS1285 and MC146818A. When substituting, verify that the replacement supports the same 24-pin SSOP package and maintains compatibility with the specific bus timing (Intel vs. Motorola) required by the host system.