Overview
The 74LS138P-E, produced by Renesas Electronics America Inc., is a high-speed 1-of-8 Decoder/Demultiplexer integrated circuit. This device is part of the 74xx family of transistor-transistor-logic gates and is fabricated using the low power Schottky barrier diode process. It is ideally suited for high-performance memory decoding and data routing applications, offering high noise resistance and low power consumption typical of TTL circuitry.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Supply Voltage (VCC) | 4.5 | 5 | 5.5 | V |
| Operating Ambient Temperature Range (TA) | -55 | 25 | 125 | °C |
| Input HIGH Voltage (VIH) | 2.0 | V | ||
| Input LOW Voltage (VIL) | 0.7 (54LS), 0.8 (74LS) | V | ||
| Output Current — High (IOH) | -0.4 | mA | ||
| Output Current — Low (IOL) | 4.0 (54LS), 8.0 (74LS) | mA | ||
| Propagation Delay Time (tPLH, tPHL) | 2-40 ns | ns | ||
| Power Dissipation | 32 mW | mW |
Key Features
- Designed for high-speed operation using Schottky barrier diode process.
- Decoding capability with three binary weighted inputs (A0, A1, A2) and eight mutually exclusive active LOW outputs (O0–O7).
- Multiple input enables: two active LOW (E1, E2) and one active HIGH (E3) for easy parallel expansion.
- ESD protection with input clamp diodes.
- Uniform propagation delays.
- Supply voltage range from 4.5V to 5.5V.
- Inputs allow voltages higher than VCC.
- Low power consumption: typical 32 mW.
- Schottky clamped for high performance and to contain line ringing).
- Operating temperature range: -55°C to +125°C).
Applications
- High-performance memory decoding and data routing.
- Line decoders and demultiplexers).
- Memory circuits and servers).
- Digital systems and telecom circuits).
Q & A
- What is the primary function of the 74LS138 IC?
The primary function of the 74LS138 IC is to decode or demultiplex, converting three binary inputs into eight mutually exclusive outputs.
- How many enable inputs does the 74LS138 IC have?
The 74LS138 IC has three enable inputs: two active LOW (E1, E2) and one active HIGH (E3).
- What is the typical power dissipation of the 74LS138 IC?
The typical power dissipation of the 74LS138 IC is 32 mW.
- What is the operating temperature range of the 74LS138 IC?
The operating temperature range of the 74LS138 IC is from -55°C to +125°C.
- How can the 74LS138 IC be used for demultiplexing?
The 74LS138 IC can be used as an 8-output demultiplexer by using one of the active LOW Enable inputs as the data input and the other Enable inputs as strobes.
- What is the propagation delay time of the 74LS138 IC?
The propagation delay time of the 74LS138 IC ranges from 2 to 40 ns depending on the load conditions.
- How can multiple 74LS138 ICs be expanded for higher decoding capabilities?
Multiple 74LS138 ICs can be expanded to create higher decoding capabilities, such as a 1-of-24 decoder using three LS138 devices or a 1-of-32 decoder using four LS138s and one inverter.
- What kind of protection does the 74LS138 IC have against static discharge?
The 74LS138 IC has ESD protection with input clamp diodes connected to VCC and ground.
- What are the typical output current capabilities of the 74LS138 IC?
The 74LS138 IC can drive up to 10 low-power Schottky TTL equivalent loads, with output currents of up to 8 mA for low-level outputs.
- In what types of applications is the 74LS138 IC commonly used?
The 74LS138 IC is commonly used in high-performance memory decoding, data routing, line decoders, memory circuits, servers, digital systems, and telecom circuits.
