BQ4845S-A4NG4

Overview

The BQ4845S-A4NG4 is a low-power parallel real-time clock (RTC) with an integrated CPU supervisor, manufactured by Texas Instruments. It provides time-of-day counting and a 100-year calendar in BCD format via a standard SRAM-like parallel interface. The device features on-chip battery-backup switchover for external SRAM, maintaining data during power loss. Key electrical parameters include a supply voltage range of 4.75 V to 5.5 V, less than 500 nA backup current, and operation temperatures from -40°C to +85°C. It includes a programmable watchdog timer, power-fail interrupt, and alarm capabilities.

Feature Summary

• Integrates a 16-byte RTC/calendar and CPU supervisor in a 28-pin SOIC package.
• Provides nonvolatile control for external SRAM via conditional chip enable (CEOUT) and backup output (VOUT).
• Includes an independent watchdog timer with programmable time-out periods ranging from 30.5 µs to 3 seconds.
• Generates interrupts for power failure, periodic events, and alarms, with alarm functionality active in battery-backup mode.

Applications

• Fax machines and copiers requiring precise timing and memory retention.
• Industrial control systems needing processor supervision and watchdog monitoring.
• Point-of-sale terminals and data loggers utilizing battery-backed SRAM.
• Computers and embedded systems requiring real-time clock and calendar functions.

Procurement Notes

Verify the specific suffix 'A4N' against the official datasheet ordering information, as standard variants are typically designated by package type (P or S), voltage tolerance (Blank or Y), and temperature range (Blank or N). Confirm availability status, as older components may be discontinued or subject to last-time buys. Ensure the source document matches the exact part number to avoid functional mismatches regarding voltage tolerances or industrial grade specifications.

Selection Notes

Select this component when a parallel interface RTC with integrated CPU supervision is required. It is suitable for designs needing direct connection to a 32.768 kHz crystal and a 3V backup battery without external diodes. Consider the 28-pin SOIC package for surface-mount applications. Ensure the system voltage falls within the 4.75 V to 5.5 V range for the bq4845 variant. Verify that the external SRAM requirements align with the CEOUT and VOUT switching characteristics.

Part Context

The BQ4845 series consists of parallel RTCs with CPU supervisors available in 28-pin DIP and SOIC packages. Variants include bq4845 (5% voltage tolerance) and bq4845Y (10% voltage tolerance). Temperature ranges cover commercial (0°C to +70°C) and industrial (-40°C to +85°C) grades. The G4 suffix indicates lead-free and RoHS-compliant manufacturing. This family is designed for microprocessor peripherals requiring timekeeping and memory protection.

Replacement Considerations

Publicly confirmed substitute part numbers for BQ4845S-A4NG4 are not identified in the provided documentation. Users should consult Texas Instruments application notes or distributor cross-reference tools for compatible alternatives with similar parallel interfaces and watchdog features.