BQ4845S-A4NTRG4

Overview

The BQ4845S-A4NTRG4 is a low-power microprocessor peripheral integrating a real-time clock, 100-year calendar, and CPU supervisor in a 28-pin SOIC package. It operates on a +5V supply (4.75V to 5.5V) with a parallel interface for direct connection to system data buses. The device features an on-chip battery-backup switchover circuit that maintains timekeeping and external SRAM data using a 3V backup cell. Key electrical characteristics include less than 500nA of clock operation current in backup mode and a power-fail interrupt warning. It provides nonvolatile control for external SRAM via conditional chip enable outputs.

Feature Summary

• Integrates a real-time clock counting seconds through years in BCD format with automatic leap year adjustment.
• Includes a CPU supervisor with power-on reset valid to VCC = VSS and a programmable independent watchdog timer.
• Features on-chip battery-backup switchover with nonvolatile control for external SRAM write-protection.
• Generates interrupts for power-fail warnings, programmable periodic intervals (30.5μs to 500ms), and alarm conditions.

Applications

• Fax machines
• Copiers
• Industrial control systems
• Point-of-sale terminals
• Data loggers

Procurement Notes

Verify the specific suffix 'TRG4' against the official Texas Instruments datasheet to confirm tape-and-reel packaging and RoHS compliance status. Confirm the industrial temperature range (-40°C to +85°C) associated with the 'N' designation. Ensure the source document explicitly lists this exact part number as available or discontinued, as ordering suffixes can alter availability or environmental certifications without changing core functionality.

Selection Notes

Select this component when a parallel interface RTC with integrated CPU supervision is required for 5V systems. It is suitable for designs needing nonvolatile external SRAM management during power failures. Verify compatibility with the target microprocessor's bus timing requirements, specifically address access times and write recovery periods. Ensure the application supports a 32.768kHz crystal load capacitance of 6pF and has space for a 3V backup battery input.

Part Context

This part belongs to the bq4845 family of Real-Time Clocks with CPU Supervisors from Texas Instruments. The 'S' indicates a 28-pin SOIC package, while 'N' denotes the industrial temperature range. The 'TRG4' suffix typically signifies tape-and-reel packaging and lead-free/RoHS compliance. This series is designed to replace discrete RTC and supervisor circuits by combining timekeeping, calendar functions, and memory protection in a single IC.

Replacement Considerations

Publicly confirmed substitute part numbers are not provided in the verified source material. Users should consult the latest Texas Instruments documentation for cross-reference information or updated product recommendations, as specific replacement mappings are not included in the provided datasheet excerpt.