BQ4845S-A4G4

Overview

The BQ4845S-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 features a parallel interface with 16 bytes of nonvolatile control for external SRAM. The device operates on a +5V supply (4.75V to 5.5V) with less than 500nA backup current. Key functions include an independent watchdog timer, power-fail interrupt, programmable periodic and alarm interrupts, and battery-low warning. It supports direct connection to a 32.768kHz crystal and a 3V backup battery.

Feature Summary

• Integrates RTC, 100-year calendar, and CPU supervisor in 28-pin SOIC
• On-chip battery-backup switchover with <500nA backup mode current
• Independent watchdog timer with programmable time-out period
• Programmable periodic interrupt (30.5μs to 500ms) and alarm interrupt

Applications

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

Procurement Notes

Verify the specific suffix 'A4G4' against the official Texas Instruments datasheet PN484501.eps. The standard commercial temperature range part is designated as bq4845, while the industrial range (-40°C to +85°C) is bq4845N. Confirm that the 'A4' designation does not imply a restricted or obsolete variant before procurement.

Selection Notes

Select this component for applications requiring a parallel interface RTC with integrated CPU supervision. Ensure the system design accommodates the 28-pin SOIC footprint. Verify compatibility with the required 32.768kHz crystal specifications (DT-26 or equivalent) and confirm that the external SRAM write-protection logic aligns with the CEOUT pin behavior during power transitions.

Part Context

This part belongs to the bq4845 family from Texas Instruments. The 'S' indicates a 28-pin SOIC package. The base model bq4845 offers 5% voltage tolerance, while bq4845Y offers 10%. The 'N' suffix denotes the industrial temperature range (-40°C to +85°C), whereas the standard commercial range is 0°C to +70°C.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. Users should consult Texas Instruments for current alternatives or verify if the bq4845YS-A4TRG4 serves as a compatible package/variant replacement.