DS1321

Controllers Overview

The DS1321 is a flexible nonvolatile memory controller with an integrated lithium battery monitor. It converts CMOS SRAMs into nonvolatile memory by automatically switching to battery backup during power failures and unconditionally write-protecting the SRAM when VCC is out of tolerance. The device supports up to four SRAMs in three configurable bank modes, monitors battery voltage for end-of-life warnings, and provides processor reset signals. Operating temperatures range from -40°C to +85°C.

Controllers Feature Summary

• Converts CMOS SRAMs into nonvolatile memory with automatic battery backup switching
• Unconditionally write-protects SRAM when VCC is out of tolerance
• Monitors lithium cell voltage and signals low-battery conditions via open-drain output
• Resets processor during power failure and holds reset during system power-up

Controllers Applications

• Battery-backed SRAM modules
• Nonvolatile memory systems requiring power-fail protection
• Processor-based systems needing power monitoring and reset generation

Controllers Procurement Notes

Verify package type (PDIP, SO, or TSSOP) and suffix (+ for lead-free/RoHS-compliant). Confirm operating temperature range (-40°C to +85°C). Check datasheet for specific electrical characteristics relevant to your application. Ensure pull-up resistors are connected to open-drain outputs (BW, RST) for proper operation.

Controllers Selection Notes

Select based on required SRAM configuration (Mode 0, 1, or 2) and package preference. Consider TOL pin setting for power-fail detection threshold (5% or 10%). Verify supply voltage compatibility (4.75V to 5.5V). Ensure battery voltage range (2.0V to 6.0V) matches the selected lithium cell.

Controllers Part Context

The DS1321 belongs to the family of flexible nonvolatile controllers designed to simplify the integration of SRAM with battery backup. It addresses common issues like data loss during power transitions and battery depletion. The device integrates power monitoring, write protection, and battery health checking into a single CMOS circuit.

Controllers Replacement Considerations

DS1321S+ (16-SOIC), DS1321E+ (20-TSSOP), DS1321+ (16-PDIP)

Controllers FAQ

How does the DS1321 handle battery replacement?

The DS1321 requires a minimum time duration between old battery detachment and new battery attachment (tBDBA) to deactivate the Battery Warning signal. If not met, the new battery must be detached and reattached to clear the warning.

What is the Freshness Seal Mode?

Freshness Seal Mode prevents battery drain during storage and shipping. The device only provides battery-backup power after VCCI exceeds VCCTP, ensuring the battery is not used until the system is activated for the first time.