The Maxim DS1312S is a RAM Memory Controller.The DS1312 Nonvolatile Controller with Battery Monitor is a CMOS circuit which solves the applicationproblem of converting CMOS RAM into nonvolatile memory. Incoming power is monitored for an out-of-tolerance condition. When such a condition is detected, chip enable is inhibited to accomplish writeprotection and the battery is switched on to supply the RAM with uninterrupted power. Special circuitry uses a low-leakage CMOS process which affords precise voltage detection at extremely low batteryconsumption. In addition to battery-backup support, the DS1312 performs the important function of monitoring theremaining 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 majorityof its life, accurate battery monitoring requires loaded-battery voltage measurement. The DS1312 performs such measurement by periodically comparing the voltage of the battery as it supports an internalresistive load with a carefully selected reference voltage. If the battery voltage falls below the referencevoltage under such conditions, the battery will soon reach end-of-life. As a result, the Battery Warningpin is activated to signal the need for battery replacement.
