DS1211

Nonvolatile Controller X 8 Chip

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Overview

Controller circuitry with monitoring and logic functions to make CMOS RAM nonvolatile
Controls up to 8 memories
Monitors V_cc and write-protects when out of tolerance
Consumes less than 100nA battery current
Tests battery condition on power-up
Supports redundant batteries
Thermal operating ranges:
- DS1211: 0°C to +70°C
- DS1211-IND: -40° to +85°C
Voltage/tolerances: 5V ±5% or ±10%

The DS1211 Nonvolatile Controller x8 Chip performs five circuit functions required to render standard CMOS RAM nonvolatile:

Monitor V_cc using a precise comparator that detects power-fail and inhibits chip-enable

Monitor battery status and warn the processor of low status

Switch power between a battery and V_cc, whichever is greater

Write-protect data

Provide for automatically switching between two batteries Power-fail detection occurs in the range of 4.75V to 4.5V with the tolerance Pin 3 grounded. If Pin 3 in connected to V_cco, then power-fail detection occurs in the range of 4.5 volts to 4.25 volts.

By combining the DS1211 nonvolatile controller/decoder chip and lithium batteries, nonvolatile RAM operation can be achieved for up to eight CMOS memories.