DS1556W-120IND

Real Time Clock Overview

The DS1556W-120IND+ is a nonvolatile, Y2K-compliant real-time clock/calendar integrated with 128KB static RAM. Operating at 3.3V within an industrial temperature range of -40°C to +85°C, it utilizes a parallel interface and 32-pin EDIP package. The device integrates a lithium energy source and crystal, providing over 10 years of data retention without power. It features programmable alarms, watchdog timers, and automatic leap-year compensation.

Real Time Clock Feature Summary

• Integrated 128KB NV SRAM with RTC registers mapped to the top 16 memory locations
• Y2K-compliant BCD-coded calendar with automatic leap-year correction valid through 2100
• Internal lithium battery ensures >10 years data retention; battery disconnected until first power application
• Programmable alarm and watchdog timer with interrupt or reset output capabilities

Real Time Clock Applications

• Industrial systems requiring precise timekeeping in harsh environments
• Data logging equipment needing nonvolatile timestamping
• Embedded controllers utilizing parallel bus interfaces for system management

Real Time Clock Procurement Notes

Verify the specific suffix IND+ confirms the industrial temperature grade (-40°C to +85°C) and lead-free status. Confirm the W variant corresponds to the 32-pin EDIP package rather than the PowerCap module. Ensure compatibility with 3.3V logic levels as specified for this model number.

Real Time Clock Selection Notes

Select this component when a combined RTC and substantial nonvolatile memory buffer is required on a single parallel bus. The 3.3V supply requirement distinguishes it from the 5V DS1556 variants. Consider the 32-pin DIP form factor for through-hole mounting if surface-mount PowerCap options are unsuitable.

Real Time Clock Part Context

This part belongs to the Maxim Integrated DS1556 family of timekeeping RAMs. The 'W' designation indicates the 3.3V operating voltage version, while 'IND' specifies the extended industrial temperature range. It serves as a direct replacement for older Dallas Semiconductor RTC modules in legacy designs.

Real Time Clock Replacement Considerations

Direct replacements include other DS1556 variants with matching voltage and package constraints. Verify pinout compatibility when substituting between 5V and 3.3V versions, as VCC requirements differ. Check for equivalent timing parameters if replacing faster access time devices.