BQ4845YP-A4E3

Overview

The BQ4845YP-A4E3 is a parallel real-time clock (RTC) with an integrated CPU supervisor, manufactured by Texas Instruments. It provides time-of-day and calendar functions in BCD format, supporting up to a 100-year range with automatic leap year adjustment. The device features on-chip battery-backup switchover for external SRAM, maintaining data during power loss. Key electrical parameters include a supply voltage of 4.75V to 5.5V, less than 500nA backup current, and operation within a commercial temperature range of 0°C to +70°C. It includes a watchdog timer, programmable interrupts, and power-fail detection.

Feature Summary

• Integrates a 100-year calendar, time-of-day clock, and CPU supervisor in a single 28-pin package.
• Features on-chip battery-backup switchover circuitry to maintain external SRAM nonvolatility.
• Includes an independent watchdog timer with programmable time-out periods ranging from 1.5s to 3s.
• Generates interrupts for power-fail, periodic events, and alarm conditions, with alarm capability active in battery-backup mode.

Applications

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

Procurement Notes

Verify the specific suffix 'A4E3' against the official datasheet ordering information. The standard documentation lists 'P' for 28-pin DIP and 'Y' for 10% voltage tolerance. Confirm that the 'E3' suffix denotes lead-free compliance or specific packaging variations without altering the core functionality. Ensure the component matches the commercial temperature grade (0°C to +70°C) required for the application.

Selection Notes

Select this component when a parallel interface RTC with integrated CPU supervision is required. It is suitable for systems needing direct connections to 32.768kHz crystals and 3V backup batteries. Consider the 28-pin PDIP or SOIC package availability. Verify that the microprocessor system supports the parallel bus timing requirements, specifically the address access time and write recovery times specified in the AC characteristics.

Part Context

The BQ4845 series is designed as a low-power microprocessor peripheral. The 'Y' variant indicates a 10% voltage tolerance compared to the standard 5% version. The device replaces discrete RTC and supervisor components, simplifying board design. It is part of Texas Instruments' legacy portfolio for industrial and consumer electronics requiring reliable timekeeping and system monitoring.

Replacement Considerations

Direct pin-compatible replacements may be limited due to the specific parallel interface and supervisor integration. Review the BQ4845YS-A4N or similar variants for equivalent functionality. Cross-reference with other parallel RTCs if the CPU supervisor feature is not strictly required. Verify that any substitute maintains the same 28-pin package dimensions and electrical specifications.