3.3V Flexible Nonvolatile Controller with Lithium Battery Monitor

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.

* 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