SMJ68CE16L-55JDM Legacy Hermetic 128K×8 CMOS Static RAM (SRAM) Overview
The SMJ68CE16L-55JDM from Texas Instruments is a high-reliability 128K×8 static random-access memory (SRAM) engineered for legacy industrial, aerospace, and defense systems. Part of TI’s trusted portfolio of hermetic memory components, it delivers 快速、无刷新临时数据存储-是速度、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、55ns 的存取时间和宽温度范围使其成为维护需要在恶劣条件下保持稳定性能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-55JDM 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） | 55 | 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） | 85 | 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-55JDM 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 70ns plastic SRAMs with this model in our 18MHz industrial PLCs, and production line downtime from memory errors dropped by 45%,” confirms a senior engineer at a leading manufacturing technology firm.
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Its 55ns access time is 21% faster than 70ns SRAMs, eliminating data lag in mid-to-high-speed legacy systems (15–20MHz controllers). For example, a factory sensor hub using a 70ns SRAM took 1.4ms to process 300 8-bit sensor data points; switching to this 55ns model cut processing time to 1.1ms. This ensured the PLC received data in time to adjust motor speeds, reducing defective parts by 28% in high-speed assembly lines—directly boosting operational efficiency.
As a CMOS SRAM, it uses 65% less power than TTL alternatives (85mW vs. 240mW), extending backup battery life in industrial systems by 25% during power outages. This is a make-or-break benefit for safety-critical equipment like emergency shutdown controllers, where prolonged battery life prevents costly operational gaps or safety risks.
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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, complexity, and potential failure points. Its -55°C to +125°C temperature range also outperforms commercial-grade SRAMs (limited to 0°C–70°C), ensuring consistent performance in freezing warehouse sensors, hot engine bays, or coastal radar systems.
Typical Applications of SMJ68CE16L-55JDM
The SMJ68CE16L-55JDM excels in legacy and mission-critical systems where speed, ruggedness, and compatibility are non-negotiable. Key use cases include:
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- Aerospace and Defense (avionics data buffers, missile guidance system memory, satellite ground station loggers, flight test data recorders)
- Industrial Automation (15–20MHz legacy PLCs, factory sensor hubs, high-speed production line controllers, emergency shutdown systems)
- Test and Measurement (ruggedized signal generators, environmental stress test equipment, legacy oscilloscope memory modules, dynamic data acquisition tools)
- 能源与电力（石油/天然气井监测控制器、风力涡轮机传感器存储器、高压变电站数据处理器）
- Security and Surveillance (military perimeter sensor data buffers, legacy outdoor camera recording modules, radar system data storage)
德州仪器在全封闭 CMOS 存储器领域的专长
As a Texas Instruments product, the SMJ68CE16L-55JDM leverages TI’s 70+ years of leadership in industrial and military-grade semiconductors. TI’s hermetic CMOS SRAMs are not just designed for performance—they are engineered for 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 or upgraded. For businesses managing legacy infrastructure, TI’s components ensure continuity without sacrificing performance or reliability.
常见问题（FAQ）
What is the SMJ68CE16L-55JDM, and how does it support legacy industrial systems?
The SMJ68CE16L-55JDM is a 128K×8 hermetic CMOS static RAM (SRAM) designed for legacy industrial, aerospace, and defense systems. It stores temporary data without requiring power refresh (a key benefit of SRAM technology) and retains 131,072 independent 8-bit data values. Via its CMOS-compatible parallel interface, it reads and writes data in 55ns, syncing seamlessly with 15–20MHz legacy controllers (e.g., TI 54LS TTL PLCs) to ensure real-time performance without lag or data loss.
Why is 55ns access time critical for 15–20MHz industrial PLCs?
15–20MHz PLCs operate on cycles of 50–67 nanoseconds (ns) per instruction. A 55ns access time aligns perfectly with this range: it ensures the SRAM delivers data to the PLC exactly when needed, avoiding delays that disrupt control commands. Slower 70ns SRAMs create a 10–20ns lag per cycle, which accumulates over hundreds of instructions to cause 10–20ms delays. These delays can misalign production line conveyors, miscalculate sensor readings, or even trigger false safety alerts—all of which lead to downtime or defective products.
JDM-32 套件如何提高恶劣环境下的可靠性？
The JDM-32 package is a hermetic ceramic J-lead dual in-line package (DIP) — a design optimized for harsh conditions. Unlike plastic DIPs (which absorb moisture and corrode over time), the JDM-32’s ceramic enclosure is sealed with an inert gas, blocking contaminants like salt (coastal environments), dust (factories), or chemicals (oil/gas sites) from reaching the chip. Its J-lead pins also form larger, more vibration-resistant solder joints with PCBs than straight pins, reducing failure risk in high-vibration systems like factory robots or aircraft.
What advantages does CMOS technology offer over TTL for this SRAM?
CMOS technology delivers two key benefits over TTL (Transistor-Transistor Logic) for this SRAM: lower power consumption and better noise immunity. At 85mW (typical quiescent power), it uses 65% less energy than TTL SRAMs (which consume ~240mW), extending battery life in backup-powered systems. It also has a wider noise margin (0.4V for low levels, 0.5V for high levels) vs. TTL’s 0.3V margin, making it more resistant to electrical interference from factory motors or radar systems—cutting data corruption errors by 40%.
Is the SMJ68CE16L-55JDM compatible with mixed-signal legacy systems (TTL + CMOS)?
Yes, it is fully compatible with mixed-signal legacy systems that use both TI 54LS TTL controllers and 74HC/74HCT CMOS sensors. Its CMOS input/output levels are TTL-compatible (VIL ≤ 0.8V, VIH ≥ 2.0V), so it can read data from CMOS sensors and send commands to TTL controllers without needing logic level translators. Additionally, it fits existing JDM-32 sockets, so technicians can replace older SRAMs without modifying PCBs—saving time and avoiding the cost of redesigning legacy infrastructure.
