DS1321

Flexible Nonvolatile Controller with Lithium Battery


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Description

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.
DS1321: Functional Block Diagram DS1321: 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 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
  • Optional 5% or 10% power-fail detection
  • 16-pin PDIP, 16-pin SO and 20-pin TSSOP packages
  • Industrial temperature range of -40°C to +85°C
Part NumberCE Cntrl.Smart Socket w/Int. Batt.Li Batt. MonitorPwr. Fail OutRAMs ControlledVSUPPLY
(V)
Package/PinsOper. Temp.
(°C)
Budgetary
Price
See Notes
DS1321 YesNoYesYes45
PDIP/16
SOIC (N)/16
TSSOP/20
-40 to +85$5.26 @1k
See All Non-Volatile RAM Controllers (6)
Pricing 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 and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Technical Documents

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

Quality and Environmental Data

Product Reliability Reports: DS1321.pdf 
Lead-Free Package Tin (Sn) Whisker Reports

Additional Resources

UL Certified

CAD Symbols and Footprints

  • DS1321+
  • DS1321E+
  • DS1321S+
  • DS1321S+T&R
  • Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

    Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

    Quality Management System >
    Environmental Management System >

     
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