The DS1314 Nonvolatile Controller with Battery Monitor is a CMOS circuit which solves the application
problem 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 write
protection 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 battery
consumption.
In addition to battery-backup support, the DS1314 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 DS1314
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.
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