DS1221S

Controllers Overview

The DS1221S is a nonvolatile controller and decoder chip designed to convert up to four CMOS RAMs into nonvolatile memories. It operates within a supply voltage range of 4.5V to 5.5V and features a 16-pin SOIC surface-mount package. The device includes a 2-to-4 decoder, power-fail detection at 4.25V to 4.50V, battery redundancy support for two batteries, and an optional security feature requiring a 64-bit access code.

Controllers Feature Summary

• Converts standard CMOS RAMs into nonvolatile memory systems by automatically protecting data during power loss events
• Integrates a 2-to-4 decoder capable of selecting one of four connected CMOS RAM banks
• Supports redundant battery configurations using two lithium batteries with automatic selection of the highest voltage source
• Includes an optional security mechanism that prevents unauthorized access through a mandatory 64-bit write/read verification sequence

Controllers Applications

• Battery-backed memory systems requiring data retention during power interruptions
• Industrial control applications needing protection against unauthorized memory access
• Embedded systems utilizing multiple CMOS RAM chips managed by a single controller

Controllers Procurement Notes

Verify component authenticity as this part is marked obsolete. Confirm package type matches design requirements. Check datasheet for specific ordering suffixes if industrial temperature ranges are needed. Ensure compatibility with existing CMOS RAM interfaces before procurement.

Controllers Selection Notes

Select this controller when designing systems requiring nonvolatile storage using discrete CMOS RAMs. Consider the 16-pin SOIC package for surface mount constraints. Evaluate the need for the optional security feature based on system access requirements. Verify battery voltage thresholds align with application needs.

Controllers Part Context

The DS1221S belongs to the DS1221 series of nonvolatile controllers manufactured by Analog Devices Inc./Maxim Integrated. It serves as a specialized interface between microprocessors and CMOS RAMs, ensuring data integrity during power transitions. The 'S' suffix denotes the 16-pin SOIC surface-mount package variant.

Controllers Replacement Considerations

Datasheet recommends consulting the DS1321 datasheet instead of new designs.