DS1556WP-120IND+

Real Time Clock Overview

The DS1556WP-120IND+ is a nonvolatile, Y2K-compliant timekeeping RAM module integrating a real-time clock (RTC), 128k x 8 SRAM, crystal, and lithium energy source. It operates at 3.3V with a 120ns access time in a 34-pin PowerCap package. The RTC provides century, year, month, date, day, hours, minutes, and seconds data in BCD format with automatic leap-year compensation up to 2100. Clock registers reside in the top 16 RAM locations for identical static RAM access. The device features programmable watchdog timer, alarm, power-on reset, and battery voltage-level indicator.

Real Time Clock Feature Summary

• Integrated NV SRAM, RTC, Crystal, Power-Fail Control Circuit, and Lithium Energy Source
• Y2K Compliant with Century Byte Register and Automatic Leap-Year Compensation Valid Up to 2100
• Totally Nonvolatile with Over 10 Years of Operation in the Absence of Power
• Programmable Watchdog Timer and RTC Alarm with Battery-Backup Wake-up Capability

Real Time Clock Applications

• Systems requiring precise timekeeping and nonvolatile data storage during power outages
• Industrial control systems operating in extended temperature ranges (-40°C to +85°C)
• Embedded devices needing Y2K compliance and battery-backed memory retention

Real Time Clock Procurement Notes

Verify that the separate DS9034PCX or DS9034I-PCX PowerCap module is ordered, as it is required for the 34-pin PowerCap package configuration. Confirm the industrial temperature grade (-40°C to +85°C) matches system requirements. Ensure VCC supply tolerance aligns with the device's ±10% specification for proper power-fail write protection operation.

Real Time Clock Selection Notes

Select the DS1556WP-120IND+ when surface-mount assembly is preferred over through-hole DIP packaging. This variant requires an external PowerCap module containing the crystal and battery, allowing the main silicon to be soldered before high-temperature reflow processes. Choose this part if 3.3V logic levels are standard in the target design and 120ns access speed meets interface timing constraints.

Real Time Clock Part Context

This component belongs to the Maxim Integrated DS1556 family of nonvolatile timekeeping RAMs. It shares functional similarities with the DS1251 and DS1746 series but offers specific integration of the RTC and SRAM in a single module. The 'WP' suffix denotes the 34-pin PowerCap package style, while 'IND+' indicates the industrial temperature range and lead-free/RoHS compliance.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers: None identified in verified documentation.