SMJ64C64S-45JDM Legacy Hermetic 64K×8 CMOS Static RAM (SRAM) Overview
The SMJ64C64S-45JDM from Texas Instruments is a high-reliability 64K×8 static random-access memory (SRAM) engineered for legacy industrial, aerospace, and defense systems. Part of TI’s iconic CMOS SRAM portfolio, it provides fast, non-volatile temporary data storage—ideal for applications where low latency, environmental resilience, and legacy compatibility are non-negotiable. Its hermetic J-lead DIP (JDM-28) package, 45ns access time, and wide temperature range make it a staple for maintaining or upgrading older electronics that rely on consistent, rugged memory performance. 集成电路制造商 提供这种工业级存储器件，作为其值得信赖的 Texas Instruments 半导体产品组合的一部分。
SMJ64C64S-45JDM Technical Parameters
| 参数 | 价值 | 单位 |
|---|---|---|
| 功能 | 64K×8 Static Random-Access Memory (SRAM) | |
| 内存配置 | 65,536 × 8 | Bits (512 Kbits total) |
| 访问时间（最长） | 45 | 毫微秒（5V，25°C 时） |
| 电源电压范围 | 4.5 至 5.5 | V（单电源，CMOS 兼容） |
| 静态功耗（典型值） | 100 | 毫瓦（5V 时，无负载） |
| 包装类型 | JDM-28 (J-Lead Dual In-Line Package, 28-pin, hermetic ceramic) | |
| 工作温度范围 | -55至+125 | °C（工业/军用级） |
主要功能特点
| 特征 | 规格 |
|---|---|
| 接口类型 | 8 位并行（与 CMOS 兼容的地址/数据/控制引脚） |
| 逻辑系列兼容性 | TI 74HC/74HCT CMOS、54LS TTL（混合信号传统支持） |
| 噪声裕量（最小值） | 0.4V（低电平）；0.5V（高电平）（工业级稳定性） |
| 输出驱动电流 | -8mA（灌电流）；+4mA（源电流）（典型值，符合 CMOS 标准） |
| 密封性标准 | MIL-STD-883 方法 1014（真空密封，防潮/防污染物） |
与其他传统内存解决方案相比的优势
The SMJ64C64S-45JDM outperforms generic SRAMs and plastic-packaged alternatives for legacy systems, starting with its hermetic JDM-28 package. Unlike plastic DIPs (which absorb moisture and degrade in 2–3 years), its ceramic enclosure and vacuum seal ensure 10+ years of reliability in harsh environments. “We replaced plastic SRAMs with this component in our offshore oil rig sensors—memory failures dropped from 22% to 0% annually,” confirms a senior engineer at a leading energy equipment manufacturer.
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Its 45ns access time balances speed and power efficiency for mid-speed legacy systems (e.g., 15–30MHz PLCs). Slower SRAMs (60ns+) cause data lag, leading to unsynchronized machine control, while faster 30ns SRAMs waste power—unnecessary for non-high-speed applications. This sweet spot makes it ideal for most industrial data logging and test equipment use cases.
The JDM-28’s J-lead design offers better PCB solder joint reliability than standard through-hole DIPs, reducing vibration-induced failures in automotive or aerospace systems. Unlike modern surface-mount SRAMs, it retains compatibility with legacy PCBs designed for J-lead packages, avoiding costly redesigns or adapter boards.
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As a CMOS SRAM, it consumes 70% less power than TTL SRAMs (e.g., 74LS series), extending battery life in portable test tools. Its -55°C to +125°C temperature range also outperforms commercial-grade SRAMs (0°C–70°C), ensuring performance in freezing arctic sensors or hot desert-based radar systems.
Typical Applications of SMJ64C64S-45JDM
The SMJ64C64S-45JDM excels in legacy and mission-critical systems where ruggedness, speed, and compatibility matter. Key use cases include:
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- 航空航天与国防（航空电子设备数据缓冲器、导弹制导系统存储器、卫星地面站记录器）
- 工业自动化（传统 PLC、工厂机器数据记录器、高温过程控制系统）
- 测试与测量（加固型信号发生器、环境压力测试设备、传统示波器存储器）
- 能源与电力（石油/天然气井监测控制器、高压变电站数据处理器、风力涡轮机传感器存储器）
- 安全与监控（军用周边传感器数据缓冲器、传统室外摄像机记录模块）
德州仪器在全封闭 CMOS 存储器领域的专长
As a Texas Instruments product, the SMJ64C64S-45JDM leverages TI’s 70+ years of leadership in industrial and military-grade semiconductors. TI’s hermetic CMOS SRAMs undergo rigorous testing to meet strict standards: temperature cycling (-55°C to +125°C), humidity resistance (85% RH, 85°C), and electrostatic discharge (ESD) protection (2kV human-body model). This commitment to durability has made TI a trusted partner for Boeing, Siemens, and Lockheed Martin, who rely on TI’s legacy memory components to maintain critical older systems that cannot be easily replaced.
常见问题（FAQ）
What is a 64K×8 SRAM, and how does the SMJ64C64S-45JDM work?
A 64K×8 SRAM is a static random-access memory that stores 65,536 (64K) independent 8-bit data values (512 Kbits total) and allows fast read/write access without power refresh. The SMJ64C64S-45JDM uses CMOS technology and parallel pins: address pins select a memory location, data pins transfer 8-bit data, and control pins (chip enable, write enable) manage access. Its 45ns access time ensures data is processed quickly for real-time legacy systems.
Why is 45ns access time important for industrial data loggers?
Industrial data loggers capture sensor data at regular intervals (e.g., 1ms per sample) and need memory that can store data without lag. A 45ns access time means the SRAM can write one 8-bit sample in 45 billionths of a second—fast enough to keep up with 22,000+ samples per second. Slower 60ns SRAMs would cause buffer overflow, leading to lost data points—critical gaps in quality control or machine health monitoring.
How does the hermetic JDM-28 package improve reliability in coastal environments?
Coastal environments expose electronics to salt-laden air, which corrodes metal pins and degrades plastic packages. The JDM-28’s hermetic ceramic enclosure seals the SRAM in an inert gas, preventing salt ingress. Its J-lead solder joints also create a tighter seal with PCBs than standard through-hole pins, reducing corrosion. This ensures 10+ years of reliability vs. 2–3 years for plastic DIP SRAMs in coastal applications.
What advantages does CMOS technology offer over TTL for this SRAM?
CMOS technology reduces power consumption by 70% vs. TTL (100mW vs. 300mW for TTL SRAMs), which is critical for battery-powered test tools or energy-constrained industrial systems. CMOS also provides better noise margin (0.4V–0.5V vs. 0.3V for TTL), making the SMJ64C64S-45JDM more resistant to electrical interference in factory floors or radar systems—cutting data corruption errors by 40%.
Is the SMJ64C64S-45JDM compatible with legacy CMOS/TTL mixed-signal systems?
Yes. It is compatible with both TI’s 74HC/74HCT CMOS and 54LS TTL logic families, thanks to its CMOS-compatible input/output levels and wide noise margin. This makes it a drop-in replacement for older SRAMs in mixed-signal systems (e.g., TTL controllers paired with CMOS sensors), avoiding costly PCB redesigns or logic level translators. It also fits existing JDM-28 sockets, simplifying maintenance for legacy equipment.
