3.3V Flexible Nonvolatile Controller with Lithium Battery Monitor

Simplify Making Up to Four SRAMs Nonvolatile

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The DS1323 flexible nonvolatile controller with lithium battery monitor is a CMOS circuit that solves the application problem of converting CMOS SRAMs into nonvolatile memory. Incoming power is monitored for an out-of-tolerance condition. When such a condition is detected, chip enable outputs are inhibited to accomplish write protection and the battery is switched on to supply the SRAMs with uninterrupted power. Special circuitry uses a low-leakage CMOS process that affords precise voltage detection at extremely low-battery consumption. One DS1323 can support as many as four SRAMs arranged in any of three memory configurations.

In addition to battery-backup support, the DS1323 performs the important function of monitoring the remaining capacity of the lithium battery and providing a warning before the battery reaches end-of-life. Because the open-circuit voltage of a lithium backup battery remains relatively constant over the majority of its life, accurate battery monitoring requires loaded-battery voltage measurement. The DS1323 performs such measurement by periodically comparing the voltage of the battery as it supports an internal resistive load with a carefully selected reference voltage. If the battery voltage falls below the reference voltage under such conditions, the battery will soon reach end-of-life. As a result, the Battery Warning pin is activated to signal the need for battery replacement.
DS1323: Functional Block Diagram DS1323: Functional Block Diagram Enlarge+

Key Features

  • Converts CMOS SRAM Into Nonvolatile Memory
  • Unconditionally Write Protects SRAM When VCC is Out of Tolerance
  • Automatically Switches to Battery Backup When VCC Power Failure Occurs
  • Flexible Memory Organization
    • Mode 0: 4 Banks with 1 SRAM Each
    • Mode 1: 2 Banks with 2 SRAMs Each
    • Mode 2: 1 Bank with 4 SRAMs Each
  • Monitors Voltage of a Lithium Cell and Provides Advanced Warning of Impending Battery Failure
  • Signals Low-Battery Condition on Active-Low Battery Warning Output Signal
  • Resets Processor When Power Failure Occurs and Holds Processor in Reset During System Power-Up
  • 10% Power-Fail Detection
  • Industrial Temperature Range: -40°C to +85°C

Technical Documents

App Note 3254 Battery Monitoring in NV SRAM Modules
App Note 202 NV SRAM Frequently Asked Questions
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