The DS1321 Flexible Nonvolatile Controller with Lithium Battery Monitor is a CMOS circuit which
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 which affords precise voltage
detection at extremely low battery consumption. One DS1321 can support as many as four SRAMs
arranged in any of three memory configurations.
In addition to battery-backup support, the DS1321 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 DS1321
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.
Key Features
Converts CMOS SRAM into nonvolatile
memory
Unconditionally write-protects SRAM when
VCC is out of tolerance
Automatically switches to battery backup
supply 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
Notes: **This pricing is BUDGETARY, for comparing similar parts. Prices are in
U.S. dollars and subject to change. Quantity pricing may vary
substantially and international prices may differ due to local
duties, taxes, fees, and exchange rates. For volume-specific prices
and delivery, please see the price and availability page
or contact an authorized distributor.
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