BQ4845YS-A4NTR

Overview

The BQ4845YS-A4NTR 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 parameters include less than 500nA current consumption 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 down to VSS.
• Features independent watchdog timer with programmable time-out periods ranging from 1.5s to 3s.
• 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 industrial temperature grade (-40°C to +85°C) indicated by the 'N' suffix against system requirements. Confirm the tape-and-reel packaging ('TR') matches automated assembly equipment specifications. Ensure the 28-pin SOIC footprint aligns with the PCB layout design before finalizing orders.

Selection Notes

Select this component when a parallel interface RTC with integrated CPU supervision is required. The 'Y' suffix indicates a 10% voltage tolerance, suitable for standard 5V logic systems. The 'S' package option provides surface-mount compatibility. Ensure the application utilizes a 32.768kHz crystal connected to X1/X2 pins for accurate timekeeping.

Part Context

This part belongs to the bq4845 family of real-time clocks manufactured by Texas Instruments. The specific suffixes define the package type (SOIC), temperature range (Industrial), and shipping method (Tape & Reel). It serves as a comprehensive timing and supervision solution for embedded microprocessor systems requiring reliable timekeeping during power outages.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. Verify pinout and register compatibility if considering alternative RTCs with similar parallel interfaces.