This document describes the features and characteristics of DS1225AB and DS1225AD, two models of non-volatile static RAM. These RAMs have a minimum data retention of 10 years and automatically protect data during power loss. They can directly replace 8k x 8 volatile static RAM or EEPROM, with unlimited write cycles and low-power CMOS design. They come in a standard 28-pin DIP package with read and write access times of 70 ns. Additionally, they support a full voltage range and an optional industrial temperature range.
The DS1225AB and DS1225AD are 65,536‑bit fully static nonvolatile SRAMs organized as 8192 × 8 bits. Each device includes a self‑contained lithium energy source that powers the memory when VCC is lost, providing automatic write protection and up to ten years of data retention without external power. The parts are pin‑compatible with standard 28‑pin DIP SRAMs, EPROMs, and EEPROMs, allowing direct replacement in existing designs.
Electrical specifications include a 70 ns read and write cycle time, operating voltage ranges of 4.75‑5.25 V (AB) or 4.5‑5.5 V (AD), and an industrial temperature range of –40 °C to +85 °C. The devices feature low standby current, unlimited write cycles, and optional ±5 % VCC tolerance for the AB version. Detailed timing diagrams, absolute maximum ratings, and ordering information are provided for design integration.
| Memory size | 65,536 bits (8192 × 8) |
|---|---|
| Data retention time | 10 years |
| Industrial temperature range | -40 °C to +85 °C |
| Power supply voltage (DS1225AB) | 4.75 V – 5.25 V |
| Power supply voltage (DS1225AD) | 4.5 V – 5.5 V |
| Read cycle time | 70 ns |
| Write cycle time | 70 ns |
| Write protection voltage (DS1225AB) | 4.5 V – 4.75 V |
| Write protection voltage (DS1225AD) | 4.25 V – 4.5 V |
The device is guaranteed to retain data for up to ten years without external power.
The industrial version operates from –40 °C to +85 °C.
The lithium source connects to the RAM when VCC falls below about 3 V and disconnects when VCC rises above that level.
Both read and write access times are specified as 70 ns.