BQ4845S-A4N

Overview

The BQ4845S-A4N is a low-power parallel real-time clock and CPU supervisor integrated in a 28-pin SOIC package. It provides time-of-day counting, a 100-year calendar, and nonvolatile control for external SRAM via battery backup. The device operates on a +5V supply (4.75V to 5.5V) with less than 500nA current in backup mode. Key features include an independent watchdog timer, power-fail interrupt, programmable periodic and alarm interrupts, and a microprocessor reset output that remains valid during battery backup.

Feature Summary

• Parallel RTC interface with 16 bytes of clock/calendar registers and direct connection for a 32.768kHz crystal.
• On-chip battery-backup switchover circuit maintains external SRAM data using a 3V backup cell.
• Microprocessor reset output (RST) active when VCC falls below threshold or upon watchdog timeout.
• Programmable watchdog timer with selectable time-out periods ranging from 23.4ms to 3s.

Applications

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

Procurement Notes

Verify component status as the BQ4845S-A4N may be discontinued. Confirm availability through authorized distributors or secondary markets. Ensure the industrial temperature range (-40°C to +85°C) matches system requirements. Check for lead-free compliance and RoHS status before procurement.

Selection Notes

Select this part for applications requiring a parallel interface RTC with integrated CPU supervision. The 'S' suffix indicates a 28-pin SOIC package, while 'N' denotes the industrial temperature grade. Ensure the design accommodates the required 3V backup battery input and external SRAM connections for nonvolatile memory support.

Part Context

This component belongs to the bq4845 family of real-time clocks. The bq4845 integrates a clock, calendar, and CPU supervisor. Variants include the bq4845Y with different voltage tolerances and the bq4847 which offers additional EEPROM storage capabilities alongside the RTC functions.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. Consider evaluating the bq4845YS-A4TRG4 or other members of the bq4845 series for potential compatibility, subject to pinout and parameter verification.