DESCRIPTION
The DS1220AB and DS1220AD 16k Nonvolatile SRAMs are 16,384-bit, fully static, nonvolatile SRAMs organized as 2048 words by 8 bits. Each NV SRAM has a self-contained lithium energy source and control circuitry which constantly monitors VCC for an out-of-tolerance condition. When such a condition occurs, the lithium energy source is automatically switched on and write protection is unconditionally enabled to prevent data corruption. The NV SRAMs can be used in place of existing 2k x 8 SRAMs directly conforming to the popular bytewide 24-pin DIP standard. The devices also match the pinout of the 2716 EPROM and the 2816 EEPROM, allowing direct substitution while enhancing performance. There is no limit on the number of write cycles that can be executed and no additional support circuitry is required for microprocessor interfacing.

FEATURES
■ 10 years minimum data retention in the absence of external power
■ Data is automatically protected during power loss
■ Directly replaces 2k x 8 volatile static RAM or EEPROM
■ Unlimited write cycles
■ Low-power CMOS
■ JEDEC standard 24-pin DIP package
■ Read and write access times of 100 ns
■ Lithium energy source is electrically disconnected to retain freshness until power is applied for the first time
■ Full ±10% VCC operating range (DS1220AD)
■ Optional ±5% VCC operating range (DS1220AB)
■ Optional industrial temperature range of -40°C to +85°C, designated IND