DS1251W-120

Overview

The DS1251W-120 is a 4096K nonvolatile SRAM integrated with a phantom clock real-time calendar and clock. It operates within a 3.3V supply range of 2.97V to 3.63V and supports through-hole mounting in a 32-pin EDIP package. The device provides 512KB of memory accessible via a parallel interface with a maximum access time of 120ns. It maintains timekeeping data for over ten years using an embedded lithium energy source that activates upon power failure. The component functions reliably across commercial temperatures from 0°C to +70°C.

Feature Summary

• Integrates 512K x 8 NV SRAM with automatic leap year compensation valid up to 2100
• Phantom clock tracks hundredths of seconds, minutes, hours, days, dates, months, and years
• Embedded lithium cell ensures data retention exceeding ten years without main power
• Transparent watch function allows standard RAM operations until specific serial pattern recognition

Applications

• Industrial systems requiring persistent timekeeping during power outages
• Data logging equipment needing nonvolatile storage for historical records
• Telecommunications infrastructure maintaining synchronization states
• Medical devices requiring accurate date and time stamping for patient records

Procurement Notes

Verify the specific suffix IND+ if industrial temperature ratings are required, as the base model covers commercial ranges. Confirm RoHS compliance status through official manufacturer documentation. Ensure the ordering part number matches the exact voltage and speed grade needed for the target application design.

Selection Notes

Select this component when a combined RTC and large nonvolatile memory solution is necessary. The phantom clock interface requires specific software initialization sequences involving 64-bit pattern recognition. Verify that the host system can accommodate the 32-pin DIP footprint and the associated control logic for the serial bit stream communication protocol.

Part Context

This device belongs to the DS1251 family of phantom clock modules. It serves as a direct replacement for volatile static RAM or EEPROM in legacy designs while adding precise timekeeping capabilities. The module integrates the crystal and battery internally, simplifying board layout compared to discrete components.

Replacement Considerations

The DS1251W-120 is upward compatible with the DS1248 series. Designers replacing older volatile memory should account for the phantom clock initialization overhead. Ensure the new system firmware implements the correct 64-bit write sequence to enable timekeeping functions.