Texas Instruments SMJ64C64S-45JDM 64K×8 SRAM, JDM-28 - 45ns CMOS hermético

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. Fabricante de CI oferece este componente de memória de nível industrial como parte da sua carteira de semicondutores de confiança da Texas Instruments.

SMJ64C64S-45JDM Technical Parameters

Parâmetro	Valor	Unidade
Função	64K×8 Static Random-Access Memory (SRAM)
Configuração da memória	65,536 × 8	Bits (512 Kbits total)
Tempo de acesso (máximo)	45	ns (a 5V, 25°C)
Gama de tensão de alimentação	4,5 a 5,5	V (alimentação única, compatível com CMOS)
Dissipação de potência quiescente (típica)	100	mW (a 5V, sem carga)
Tipo de embalagem	JDM-28 (J-Lead Dual In-Line Package, 28-pin, hermetic ceramic)
Gama de temperaturas de funcionamento	-55 a +125	°C (de tipo industrial/militar)

Principais caraterísticas funcionais

Caraterística	Especificação
Tipo de interface	Paralelo de 8 bits (pinos de endereço/dados/controlo compatíveis com CMOS)
Compatibilidade de famílias lógicas	TI 74HC/74HCT CMOS, 54LS TTL (mixed-signal legacy support)
Margem de ruído (mín.)	0,4V (nível baixo); 0,5V (nível alto) (estabilidade de nível industrial)
Corrente de acionamento de saída	-8mA (dissipador); +4mA (fonte) (típico, compatível com CMOS)
Hermeticity Standard	MIL-STD-883 Method 1014 (vacuum-sealed against moisture/contaminants)

Vantagens em relação a soluções alternativas de memória antiga

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.

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.

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:

• Aeroespacial e Defesa (buffers de dados de aviónica, memória do sistema de orientação de mísseis, registadores de estações terrestres de satélite)
• Automação industrial (PLCs antigos, registadores de dados de máquinas de fábrica, sistemas de controlo de processos a altas temperaturas)
• Teste e Medição (geradores de sinais robustos, equipamento de teste de stress ambiental, memória de osciloscópio antiga)
• Energy and Power (oil/gas well monitoring controllers, high-voltage substation data processors, wind turbine sensor memory)
• Segurança e vigilância (buffers de dados de sensores de perímetro militar, módulos de gravação de câmaras exteriores antigas)

Experiência da Texas Instruments em memória CMOS hermética

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.

Perguntas frequentes (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.