DS1557WP-120

Real Time Clock Overview

The DS1557WP-120 is a 4Meg (512k x 8) nonvolatile static RAM integrated with a Y2K-compliant real-time clock/calendar, lithium battery source, and power-fail control circuit. Operating at 3.3V within the commercial temperature range of 0°C to +70°C, it features a byte-wide interface where RTC registers reside in the top 16 RAM locations. The device includes programmable watchdog timer, alarm functions, and precision power-on reset. It provides over 10 years of data retention via an internal lithium cell that disconnects electrically until first power application.

Real Time Clock Feature Summary

• Integrated 512k x 8 NV SRAM with Y2K-compliant RTC, calendar, and lithium backup
• Automatic leap year compensation and BCD-coded time/date registers up to year 2100
• Programmable watchdog timer and alarm with interrupt output (IRQ/FT)
• Power-fail write protection and precision power-on reset (RST) for system safety

Real Time Clock Applications

• Data logging systems requiring long-term timestamp preservation
• Embedded controllers needing reliable real-time clock functionality
• Industrial equipment requiring watchdog timer protection
• Battery-backed memory applications with strict power-fail data integrity needs

Real Time Clock Procurement Notes

Verify the specific ordering suffix matches the required voltage and temperature grade. The DS1557WP-120 indicates a 3.3V supply and commercial temperature range. Ensure the PowerCap module (DS9034PCX+) is ordered separately if surface-mount integration is required, as the component relies on this external board for the lithium energy source connection.

Real Time Clock Selection Notes

Select the DS1557WP-120 when a 3.3V logic interface is required alongside nonvolatile timekeeping. Compare against the DS1557P-70 variants if a 5V supply or industrial temperature range (-40°C to +85°C) is necessary. Confirm that the 34-pin PowerCap package fits the PCB layout constraints, as this is the only available package type for this device family.

Real Time Clock Part Context

This component belongs to the Maxim Integrated DS1557 family of nonvolatile timekeeping RAMs. It combines standard SRAM accessibility with specialized RTC registers mapped to the highest address space. The device simplifies system design by integrating clock, calendar, and backup power management into a single IC, reducing the component count for time-sensitive embedded applications.

Real Time Clock Replacement Considerations

Direct replacements include other DS1557 variants such as DS1557P-70+ for 5V operation or DS1557WP-120IND+ for industrial temperature ranges. Verify pin compatibility and voltage levels before substitution. No cross-model functional differences exist beyond voltage and temperature specifications.