BQ3285ESSTRG4

Overview

The BQ3285ESSTRG4 is a CMOS real-time clock (RTC) and calendar IC from Texas Instruments, part of the bq3285E/L family. It provides time-of-day tracking with a 100-year calendar, alarm features, and 242 bytes of general nonvolatile SRAM. Designed for IBM AT-compatible systems, it operates on a 4.5V to 5.5V supply (bq3285E variant) with less than 0.5µA battery load. Key interfaces include multiplexed address/data lines compatible with Intel or Motorola bus timing. The device supports programmable square-wave outputs, three maskable interrupt sources, and automatic leap-year adjustment. It requires only an external 32.768kHz crystal and backup battery for operation.

Feature Summary

• 242 bytes of general nonvolatile storage with automatic power-fail write protection
• Multiplexed bus interface compatible with Intel and Motorola architectures
• Programmable square-wave output ranging from 1Hz to 32.768kHz
• Three individually maskable interrupts: periodic, alarm, and update-ended
• Alarm interrupt active in battery-backup mode for system wake-up capability

Applications

• IBM AT-compatible computer systems
• Microprocessor peripheral clock/calendar modules
• Battery-backed data logging applications
• Power management systems requiring wake-up alarms

Procurement Notes

Verify component authenticity through authorized distributors or direct manufacturer channels. Confirm RoHS compliance status as specified in current datasheets. Check for moisture sensitivity level (MSL 2) handling requirements during storage and assembly. Ensure proper ESD precautions are taken due to CMOS construction. Validate that the specific suffix 'G4' aligns with lead-free manufacturing standards if required by your assembly process.

Selection Notes

Select the bq3285E variant for 4.5V–5.5V system supplies; use bq3285L for 2.7V–3.6V systems. Ensure the host processor supports multiplexed address/data bus cycles. Verify compatibility with Intel or Motorola bus timing via the MOT pin configuration. Confirm availability of a 32.768kHz crystal with 6pF load capacitance. Check if the 24-pin SSOP package fits the PCB footprint constraints.

Part Context

The BQ3285ESSTRG4 belongs to the bq3285E/L series of low-power RTCs. The 'ESS' denotes a 24-lead SSOP package, while 'STR' indicates tape-and-reel packaging. The 'G4' suffix typically signifies lead-free and RoHS-compliant manufacturing. This component serves as a drop-in replacement for legacy RTCs like the DS1285 and MC146818A in many industrial and computing designs.

Replacement Considerations

Functionally compatible with Dallas Semiconductor DS1285 and Motorola MC146818A. Pin configurations closely match these legacy parts, facilitating direct board upgrades. Verify voltage level compatibility when replacing bq3285L (3V) with bq3285E (5V) variants, as they are not electrically interchangeable without circuit modification.