BQ4845P-A4

Overview

The BQ4845P-A4 is a low-power microprocessor peripheral integrating a real-time clock, 100-year calendar, and CPU supervisor in a 28-pin plastic DIP package. It features a parallel interface for direct connection to system buses. The device includes an on-chip battery-backup switchover circuit with nonvolatile control for external SRAM, utilizing BC and VOUT pins. Clock operation current in backup mode is less than 500nA. Supply voltage ranges from 4.75V to 5.5V, with an operating temperature range of 0°C to +70°C.

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-fail interrupt warning and microprocessor reset valid to VCC = VSS.
• Features an independent watchdog timer with programmable time-out periods ranging from 1.5s to 3s.
• Provides conditional chip enable output (CEOUT) and backup battery output (VOUT) to write-protect and power external SRAM.

Applications

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

Procurement Notes

Verify the specific suffix 'A4' against the manufacturer's official documentation to confirm exact electrical tolerances and temperature ratings. The standard datasheet defines the base bq4845 as commercial grade (0°C to +70°C) with 5% voltage tolerance. Ensure the ordered component matches the required industrial or commercial specifications before integration.

Selection Notes

Select this component for applications requiring a parallel RTC interface with integrated CPU supervision. The P suffix indicates a 28-pin PDIP package suitable for through-hole mounting. Verify that the system design accommodates the 4.75V to 5.5V supply range and provides a 3V backup cell connection on the BC pin for continuous operation during power loss.

Part Context

The BQ4845P-A4 belongs to the bq4845 family of Real-Time Clocks with CPU Supervisors manufactured by Texas Instruments. This series is designed to provide timekeeping and system monitoring functions for microprocessor-based systems. The device simplifies design by combining RTC, calendar, and supervisor functions into a single 28-pin IC.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided source material. Consult the manufacturer's latest documentation for potential cross-references or updated product recommendations.