Overview
The SN74LS138 is a 3-line to 8-line decoder/demultiplexer integrated circuit produced by Texas Instruments. This Schottky-clamped TTL MSI (Medium Scale Integration) circuit is designed for high-performance applications, particularly in memory decoding and data-routing systems. It is known for its short propagation delay times, making it suitable for use in high-speed memory systems.
Key Specifications
| Parameter | Value |
|---|---|
| Package Type | PDIP (N), SOIC (D), SOP (NS) |
| Pins | 16 |
| Operating Temperature Range (°C) | 0 to 70 |
| Voltage Supply Source | Single Supply |
| Voltage - Supply | 4.75 V ~ 5.25 V |
| Current - Output High, Low | 400µA, 8mA |
| Mounting Type | Through Hole |
| Package / Case | 16-DIP (0.300", 7.62mm), 16-SOIC, 16-SOP |
Key Features
- Designed specifically for high-speed memory decoders and data transmission systems.
- Features three enable inputs to simplify cascading and/or data reception.
- Schottky-clamped for high performance to suppress line-ringing and simplify system design.
- Fully buffered inputs, each representing only one normalized load to its driving circuit.
- Two active-low and one active-high enable inputs reduce the need for external gates or inverters.
- An enable input can be used as a data input for demultiplexing applications.
Applications
The SN74LS138 is primarily used in high-performance memory decoding and data-routing applications. It is particularly useful in:
- High-speed memory systems to minimize system decoding delays.
- Data transmission systems requiring fast and reliable decoding.
- Demultiplexing applications where an enable input can be used as a data input.
- Cascading decoders to implement larger decoding systems (e.g., 24-line or 32-line decoders) without the need for external inverters.
Q & A
- What is the primary function of the SN74LS138?
The SN74LS138 is a 3-line to 8-line decoder/demultiplexer, designed for high-performance memory decoding and data-routing applications.
- What are the key package types available for the SN74LS138?
The SN74LS138 is available in PDIP (N), SOIC (D), and SOP (NS) packages.
- What is the operating temperature range of the SN74LS138?
The operating temperature range is from 0°C to 70°C.
- What is the voltage supply range for the SN74LS138?
The voltage supply range is from 4.75 V to 5.25 V.
- What are the current output specifications for the SN74LS138?
The current output specifications are 400µA for high output and 8mA for low output.
- How do the enable inputs of the SN74LS138 simplify system design?
The two active-low and one active-high enable inputs reduce the need for external gates or inverters, making system design simpler and more efficient.
- Can the SN74LS138 be used in demultiplexing applications?
- How does the Schottky-clamped design benefit the SN74LS138?
The Schottky-clamped design suppresses line-ringing and simplifies system design, enhancing overall performance.
- What are some common applications of the SN74LS138?
- Can the SN74LS138 be cascaded to implement larger decoding systems?
