DS1557WP-120IND

Real Time Clock Overview

The DS1557WP-120IND is a nonvolatile, Y2K-compliant timekeeping RAM device integrating a real-time clock (RTC), 512k x 8 static RAM, and a lithium energy source. It operates at 3.3V with an access time of 120ns. The RTC provides century, year, month, date, day, hours, minutes, and seconds in BCD format with automatic leap year compensation valid to 2100. Features include a programmable watchdog timer, alarm, power-fail write protection, and battery voltage-level indicator. The device uses a parallel interface and is housed in a 34-pin PowerCap module.

Real Time Clock Feature Summary

• Integrated NV SRAM (512k x 8) and Real-Time Clock with Century Byte Register
• Automatic Leap Year Compensation Valid Up to the Year 2100
• Programmable Watchdog Timer and RTC Alarm with IRQ/FT Output
• Power-Fail Write Protection and Precision Power-On Reset

Real Time Clock Applications

• Systems requiring nonvolatile timekeeping and data retention
• Industrial control systems operating in -40°C to +85°C environments
• Equipment needing CPU watchdog monitoring via RST or IRQ outputs

Real Time Clock Procurement Notes

Verify the specific suffix IND+ for industrial temperature range (-40°C to +85°C) and 3.3V operation. Confirm that the required PowerCap base (DS9034PCX+) is ordered separately as it is not included with the component. Check for any manufacturer errata related to specific production revisions before finalizing design integration.

Real Time Clock Selection Notes

Select this part when a combined RTC and large NV SRAM solution is needed in a single package. Ensure the system supports parallel memory interfaces with appropriate address and data bus widths. Verify that the 3.3V supply tolerance aligns with the device's VPF and VSO thresholds for reliable power-fail detection and battery switchover.

Real Time Clock Part Context

The DS1557 belongs to the Maxim Integrated DS155x family of timekeeping RAM devices. It combines the functionality of a standalone RTC with high-density static RAM, eliminating the need for external battery-backed SRAM chips. The WP variant indicates surface-mount packaging within the PowerCap module form factor.

Real Time Clock Replacement Considerations

Direct replacements within the same family include the DS1557P-70IND+ for 5V operation or commercial temperature ranges. For different densities, consider the DS1556 series, though pinouts and capacities differ. Verify compatibility with existing PCB land patterns if substituting with other PowerCap modules.