DESCRIPTION
The DS1221 Nonvolatile Controller x 4 Chip is a CMOS circuit which solves the application problem of converting CMOS RAMs into nonvolatile memories. Incoming power is monitored for an out-of tolerance condition. When such a condition is detected, the chip enable outputs are inhibited to accomplish write protection and the battery is switched on to supply RAMs with uninterrupted power. An optional security code prevents unauthorized users from obtaining access to the memory space. The nonvolatile controller/decoder circuitry uses a low-leakage CMOS process which affords precise voltage detection at extremely low battery consumption. By combining the DS1221 with up to four CMOS memories and lithium batteries, nonvolatile operation can be achieved.

FEATURES
■ Converts CMOS RAMs into nonvolatile memories
■ Data is automatically protected during power loss
■ 2-to-4 decoder provides for up to 4 CMOS RAMs
■ Provides for redundant batteries
■ Test battery condition on power-up
■ Full ±10% operating range
■ Unauthorized access can be prevented with optional security feature
■ 16-pin 0.3-inch DIP saves PC board space
■ Optional 16-pin SOIC surface mount package
■ Optional industrial temperature range of -40°C to +85°C available