BQ4845YS-A4G4

Overview

The BQ4845YS-A4G4 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 programmable watchdog timer.

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 VSS.
• Features independent watchdog timer with programmable time-out periods ranging from 1.5s down to 375ms.
• Provides nonvolatile control for external SRAM via conditional chip enable output (CEOUT) and backup battery output (VOUT).

Applications

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

Procurement Notes

Verify the specific suffix 'A4G4' against the manufacturer's official ordering guide, as standard documentation lists 'S' for SOIC and 'N' for industrial temperature range. Confirm RoHS compliance status and lead times directly with Texas Instruments or authorized distributors, as availability may vary by region.

Selection Notes

Select this component when a parallel interface RTC with integrated CPU supervision is required. Ensure the design accommodates a 32.768kHz crystal connected to X1/X2 pins and a 3V primary backup battery on the BC pin. Verify that the system voltage remains within the 4.75V to 5.5V operating range for proper functionality.

Part Context

This part belongs to the bq4845 family of Real-Time Clocks with CPU Supervisors. The 'S' indicates a 28-pin Small Outline Integrated Circuit (SOIC) package. The 'Y' denotes a 10% voltage tolerance variant. The 'N' suffix typically indicates an industrial temperature range (-40°C to +85°C), while the blank suffix indicates commercial range (0°C to +70°C).

Replacement Considerations

Direct replacements include other parts within the bq4845 family such as the bq4845P-A4 (DIP package) or bq4845YP-A4. Check datasheets for pin compatibility and electrical specifications before substitution.