DS1321S/T&R

Overview

The DS1321S/T&R is a flexible nonvolatile controller with a lithium battery monitor, designed to convert CMOS SRAMs into nonvolatile memory. It operates within an industrial temperature range of -40°C to +85°C and accepts a supply voltage between 4.75V and 5.5V. The device supports up to four SRAM channels and features a low operating current of 50µA in battery backup mode. Packaged in a 16-pin SOIC format, it provides automatic power-fail detection and processor reset capabilities.

Feature Summary

• Converts standard CMOS SRAMs into nonvolatile memory by managing power switching between system supply and backup battery.
• Monitors lithium cell voltage to provide advanced warning of impending battery failure via an active-low output signal.
• Automatically switches to battery backup supply upon detecting power failure while unconditionally write-protecting the SRAM.

Applications

• Battery-backed data storage systems requiring nonvolatile memory
• Processor-based systems needing power-fail detection and reset generation
• Industrial equipment requiring reliable data retention during power outages

Procurement Notes

Verify that the specific ordering suffix matches the required package type, as the base part number covers multiple packages. Confirm RoHS compliance status for the specific reel variant. Ensure the design accommodates the open-drain nature of the Battery Warning and Reset outputs by including appropriate pull-up resistors. Check for any specific manufacturing date codes if long-term availability is critical.

Selection Notes

Select this component when designing systems that require converting external CMOS SRAMs into nonvolatile memory without complex logic. It is suitable for applications needing precise power-fail detection and automated battery health monitoring. Consider the available memory configurations, which allow for flexible organization of one to four SRAM banks based on the MODE pin state.

Part Context

This component belongs to the DS1321 series from Analog Devices / Maxim Integrated. It is specifically the surface-mount version packaged in a 16-pin Small Outline (SO) configuration. The series is engineered to solve application problems related to maintaining data integrity in volatile memory during power interruptions.

Replacement Considerations

DS1321E+T&R

FAQ

How does the DS1321S handle write protection during a power failure?

When VCCI falls out of tolerance, the device inhibits the four chip enable outputs to accomplish write protection, holding them high to prevent data corruption.

What is the function of the Freshness Seal Mode?

Freshness Seal Mode prevents the battery from providing backup power until VCCI exceeds the trip point, ensuring no battery energy is drained during storage or shipping before the system is first activated.