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 fast, non-refresh temporary data storage—ideal for applications where speed, environmental resilience, and legacy compatibility are non-negotiable. Its J-lead DIP (JDM-32) package, 55ns access time, and wide temperature range make it a staple for maintaining older electronics that demand consistent performance in harsh conditions. ICメーカー は、信頼性の高いテキサス・インスツルメンツ半導体のポートフォリオの一部として、この工業用グレードのメモリ・コンポーネントを提供しています。
Technical Parameters for SMJ68CE16L-55JDM Industrial SRAM
| パラメータ | 価値 | 単位 |
|---|---|---|
| 機能 | 128K×8スタティック・ランダム・アクセス・メモリ（SRAM） | |
| メモリ構成 | 131,072 × 8 | Bits (1024 Kbits / 128 Kbytes total) |
| アクセス時間（最大） | 55 | ns（5V、25℃の場合） |
| 電源電圧範囲 | 4.5から5.5 | V（単一電源、CMOS互換） |
| 静止時許容損失（代表値） | 85 | mW（5V、無負荷時） |
| パッケージタイプ | JDM-32（Jリードデュアルインラインパッケージ、32ピン、ハーメチックセラミック） | |
| 動作温度範囲 | -55 から +125 | °C (工業用/軍用グレード) |
主な機能的特徴
| 特徴 | 仕様 |
|---|---|
| インターフェース・タイプ | 8ビットパラレル（CMOS互換アドレス/データ/制御ピン） |
| ロジックファミリーの互換性 | TI 74HC/74HCT CMOS、54LS TTL（ミックスドシグナル・レガシーシステム対応） |
| ノイズ・マージン（最小） | 0.4V（ローレベル）、0.5V（ハイレベル）（産業グレードの安定性） |
| 出力ドライブ電流 | -8mA（シンク）、+4mA（ソース）（代表値、CMOS準拠） |
| 信頼性基準 | MIL-STD-883準拠（気密性、温度サイクル、ESD保護） |
他のレガシー・メモリー・ソリューションにない利点
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)
- Energy and Power (oil/gas well monitoring controllers, wind turbine sensor memory, high-voltage substation data processors)
- Security and Surveillance (military perimeter sensor data buffers, legacy outdoor camera recording modules, radar system data storage)
ハーメチックCMOSメモリにおけるテキサス・インスツルメンツの専門知識
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.
よくある質問（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.
How does the JDM-32 package improve reliability in harsh environments?
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.
このSRAMにとって、CMOS技術はTTLに比べてどのような利点がありますか？
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.