SMJ68CE16L-45JDM Legacy Hermetic 128K×8 CMOS Static RAM (SRAM) Overview
The SMJ68CE16L-45JDM from Texas Instruments is a high-reliability 128K×8 static random-access memory (SRAM) engineered for high-speed legacy industrial, aerospace, and defense systems. Part of TI’s trusted portfolio of hermetic memory components, it delivers 超快、无刷新临时数据存储-它是对速度、环境适应性和传统兼容性要求极高的应用的理想之选。其 J 引线 DIP（JDM-32）封装、45ns 访问时间和宽温度范围使其成为在苛刻条件下维护需要一致、高性能数据处理的老式电子设备的主要选择。 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。
Technical Parameters for SMJ68CE16L-45JDM Industrial SRAM
| 参数 | 价值 | 单位 |
|---|---|---|
| 功能 | 128K×8 静态随机存取存储器 (SRAM) | |
| 内存配置 | 131,072 × 8 | 比特（1024 千比特/共 128 千字节） |
| 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） | 88 | 毫瓦（5V 时，无负载） |
| 包装类型 | JDM-32（J 引线双列直插式封装，32 引脚，密封陶瓷） | |
| 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（支持混合信号传统系统） |
| 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） |
| 可靠性标准 | 符合 MIL-STD-883（密封性、温度循环、ESD 保护） |
与其他传统内存解决方案相比的优势
The SMJ68CE16L-45JDM outperforms generic SRAMs, plastic-packaged alternatives, and slower memory options, starting with its hermetic JDM-32 package. Unlike plastic DIPs (which degrade in 2–3 years due to moisture or corrosion), its ceramic enclosure and vacuum seal ensure 10+ years of reliability—critical for systems where replacement is costly or dangerous. “We replaced 60ns plastic SRAMs with this model in our 22MHz aerospace radar systems, and target tracking errors dropped by 32%,” confirms a senior engineer at a leading defense electronics firm.
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Its 45ns access time is 25% faster than 60ns SRAMs, eliminating micro-lag in high-speed legacy systems (20–25MHz controllers). For example, a factory sensor hub using a 60ns SRAM took 1.2ms to process 250 8-bit sensor data points; switching to this 45ns model cut processing time to 0.9ms. This ensured the PLC received data in time to adjust motor speeds, reducing defective parts by 33% in high-speed assembly lines—directly boosting throughput and lowering waste.
As a CMOS SRAM, it uses 62% less power than TTL alternatives (88mW vs. 230mW), extending backup battery life in industrial systems by 29% during power outages. This is a critical benefit for safety-critical equipment like emergency shutdown controllers, especially in remote sites (e.g., offshore wind farms) where backup power is limited.
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The JDM-32’s J-lead design creates stronger solder joints than standard through-hole pins, reducing vibration-induced failures in automotive or aerospace systems. Unlike modern surface-mount SRAMs, it fits legacy PCBs designed for J-lead packages—avoiding costly redesigns or adapter boards that add size and failure risks. Its -55°C to +125°C temperature range also outperforms commercial-grade SRAMs (0°C–70°C), ensuring performance in freezing arctic sensors, hot engine bays, or coastal radar systems.
Typical Applications of SMJ68CE16L-45JDM
The SMJ68CE16L-45JDM excels in legacy and mission-critical systems where ultra-fast speed, ruggedness, and compatibility are non-negotiable. Key use cases include:
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- Aerospace and Defense (avionics telemetry buffers, missile guidance system memory, radar target tracking loggers, high-speed flight test data recorders)
- Industrial Automation (20–25MHz legacy PLCs, factory high-speed sensor hubs, precision machine tool controllers, automotive assembly line sync systems)
- Test and Measurement (high-frequency oscilloscopes, dynamic strain gauges, ruggedized signal generators, environmental stress test equipment)
- Energy and Power (oil/gas well high-speed monitoring controllers, wind turbine pitch control sensor memory, high-voltage substation data processors)
- Security and Surveillance (military perimeter radar data buffers, legacy high-speed camera recording modules, threat detection system memory)
德州仪器在全封闭 CMOS 存储器领域的专长
As a Texas Instruments product, the SMJ68CE16L-45JDM leverages TI’s 70+ years of leadership in industrial and military-grade semiconductors. TI’s hermetic CMOS SRAMs are engineered for both performance and longevity—each unit undergoes rigorous testing to meet strict global standards: temperature cycling (-55°C to +125°C for 1,000 cycles), humidity resistance (85% RH at 85°C for 1,000 hours), and electrostatic discharge (ESD) protection (2kV human-body model, per MIL-STD-883 Method 3015).
This commitment to durability has made TI a trusted partner for industry leaders like Boeing (aerospace), Siemens (industrial automation), and Lockheed Martin (defense)—all of which rely on TI’s legacy memory components to maintain critical older systems that cannot be easily replaced. For businesses managing high-speed legacy infrastructure, TI’s components ensure continuity without sacrificing speed, efficiency, or reliability.
常见问题（FAQ）
What is the SMJ68CE16L-45JDM, and how does it support high-speed legacy systems?
The SMJ68CE16L-45JDM is a 128K×8 hermetic CMOS SRAM designed for high-speed legacy industrial, aerospace, and defense systems. It stores temporary data without power refresh (a core SRAM benefit) and retains 131,072 independent 8-bit values. Via its CMOS-compatible parallel interface, it reads/writes data in 45ns—fast enough to sync with 20–25MHz controllers (e.g., TI 54LS TTL PLCs) and eliminate micro-lag that disrupts high-speed operations.
为什么 45ns 的访问时间对 20-25MHz 的工业 PLC 至关重要？
20–25MHz PLCs operate on 40–50ns cycles. A 45ns access time aligns perfectly with this range, ensuring the SRAM delivers data exactly when the PLC needs it. Slower 60ns SRAMs create a 10–20ns lag per cycle, which accumulates over 1,000 cycles to cause 10–20ms delays. These delays misalign high-speed conveyors, miscalculate sensor readings, or trigger false safety alerts—leading to costly downtime or defective products.
JDM-32 套件如何提高恶劣环境下的可靠性？
JDM-32 的密封陶瓷外壳将 SRAM 封闭在惰性气体中，阻隔了盐分（沿海）、灰尘（工厂）或化学物质（油气田），这些物质会使塑料 DIP 退化。它的 J 引线引脚可与印刷电路板形成较大的抗震焊点，这对工厂机器人或飞机至关重要，因为振动会破坏标准的通孔焊点。与塑料 SRAM 的 2-3 年寿命相比，这种设计可确保 10 年以上的使用寿命。
对于这种 SRAM，CMOS 技术比 TTL 技术有哪些优势？
CMOS technology cuts power use by 62% (88mW vs. 230mW for TTL), extending backup battery life in critical systems. It also has a wider noise margin (0.4V–0.5V vs. TTL’s 0.3V), making it more resistant to electrical interference from factory motors or radar—reducing data corruption errors by 42% and minimizing unplanned downtime.
Is the SMJ68CE16L-45JDM compatible with mixed-signal legacy systems (TTL + CMOS)?
它能与使用 TI 54LS TTL 控制器和 74HC/74HCT CMOS 传感器的混合信号系统无缝配合。它的 CMOS I/O 电平与 TTL 兼容（VIL ≤ 0.8V，VIH ≥ 2.0V），因此无需逻辑转换器。它还适合现有的 JDM-32 插座，技术人员无需修改 PCB 即可替换旧的 SRAM，从而节省了时间，避免了昂贵的基础架构大修。
