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.

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