Overview
The SN74ALS138ADBR is a high-speed 1-of-8 decoder/demultiplexer produced by Texas Instruments. This device is part of the Advanced Low-Power Schottky (ALS) family and is designed for high-performance applications, particularly in memory decoding and data transmission systems. It features three binary weighted inputs and provides eight mutually exclusive active-low outputs. The device is fabricated using the Schottky barrier diode process, ensuring high speed and low power consumption.
Key Specifications
| Parameter | Description |
|---|---|
| Manufacturer | Texas Instruments |
| Part Number | SN74ALS138ADBR |
| Category | Logic/Signal Switches, Multiplexers, Decoders |
| Package | SOIC (D) - 16 pins |
| Supply Voltage (VCC) | 4.5V to 5.5V |
| Operating Temperature Range | 0°C to 70°C |
| Input HIGH Voltage (VIH) | 2.0V |
| Input LOW Voltage (VIL) | 0.7V (54 series), 0.8V (74 series) |
| Output Current — High (IOH) | -0.4mA |
| Output Current — Low (IOL) | 4.0mA (54 series), 8.0mA (74 series) |
| Propagation Delay E3 (Enable to Output) | 17ns to 38ns |
Key Features
- High-Speed Operation: Fabricated with the Schottky barrier diode process for high-speed performance.
- Multiple Enable Inputs: Three enable inputs (two active-low and one active-high) for easy parallel expansion and cascading.
- Demultiplexing Capability: Can be used as an 8-output demultiplexer by using one of the active-low enable inputs as the data input.
- Low Power Dissipation: Typical power dissipation of 32 mW.
- Input Clamp Diodes: High-speed termination effects are limited by input clamp diodes.
- Compatibility: Fully compatible with all Motorola TTL families.
Applications
- High-Speed Memory Decoding: Ideal for high-speed bipolar memory chip select address decoding.
- Data Transmission Systems: Suitable for high-performance data-routing applications requiring short propagation delay times.
- Parallel Expansion: Can be expanded to a 1-of-24 decoder using three LS138 devices or to a 1-of-32 decoder using four LS138 devices and one inverter.
Q & A
- What is the primary function of the SN74ALS138ADBR?
The SN74ALS138ADBR is a high-speed 1-of-8 decoder/demultiplexer.
- What is the typical power dissipation of the SN74ALS138ADBR?
The typical power dissipation is 32 mW.
- How many enable inputs does the SN74ALS138ADBR have?
It has three enable inputs: two active-low and one active-high.
- What is the operating temperature range of the SN74ALS138ADBR?
The operating temperature range is from 0°C to 70°C.
- Can the SN74ALS138ADBR be used as a demultiplexer?
Yes, it can be used as an 8-output demultiplexer by using one of the active-low enable inputs as the data input.
- How can the SN74ALS138ADBR be expanded for more outputs?
It can be expanded to a 1-of-24 decoder using three LS138 devices or to a 1-of-32 decoder using four LS138 devices and one inverter.
- What is the propagation delay for the enable to output signal?
The propagation delay ranges from 17ns to 38ns.
- Is the SN74ALS138ADBR compatible with other TTL families?
Yes, it is fully compatible with all Motorola TTL families.
- What is the supply voltage range for the SN74ALS138ADBR?
The supply voltage range is from 4.5V to 5.5V.
- What are the input clamp diodes used for in the SN74ALS138ADBR?
The input clamp diodes are used to limit high-speed termination effects.
