The CD74HCT138M96 is a high-speed CMOS (Complementary Metal-Oxide-Semiconductor) logic device that functions as a 3-to-8 line decoder/demultiplexer. This device is part of the 74HC/HCT family, which is known for its high-speed operation and low power consumption. The CD74HCT138 is widely used in various digital circuits for decoding applications, enabling efficient signal routing and management.
## Key Features
1. Functionality:
- The CD74HCT138 takes a 3-bit binary input and decodes it into one of eight mutually exclusive outputs. It can also be used as a demultiplexer with one active output based on the input combination.
2. Low Power Consumption:
- Designed to operate at low power levels, making it suitable for battery-operated devices and energy-efficient applications.
3. High-Speed Operation:
- Capable of operating at high speeds, ensuring quick response times in digital systems.
4. Active-Low Outputs:
- The outputs are active LOW, meaning that when a particular output is selected, it goes to a low state (0), while all other outputs remain high (1).
5. Enable Inputs:
- The device includes enable inputs that allow for additional control over the decoding process, enabling or disabling the entire circuit as needed.
6. Wide Supply Voltage Range:
- Compatible with a wide range of supply voltages, making it versatile for various applications.
7. Temperature Range:
- Suitable for operation in a broad temperature range, enhancing reliability in diverse environments.
## Specifications
| Parameter | Value |
|------------------------------|---------------------------------------------------|
| Logic Family | HCT (High-speed CMOS) |
| Number of Inputs | 3 |
| Number of Outputs | 8 |
| Output Type | Active LOW |
| Supply Voltage (Vcc) | 4.5V to 5.5V |
| Input Voltage (Vih) | Vcc * 0.7 (max), typically 2.1V at Vcc = 3V |
| Input Voltage (Vil) | Vcc * 0.3 (max), typically 0.9V at Vcc = 3V |
| Propagation Delay | 15 ns (typical at Vcc = 5V) |
| Power Dissipation | 1 mW (typical, static) |
| Operating Temperature Range | -40°C to +125°C |
| Input Current (Iin) | ±1 µA (maximum) |
| Fan-out | 10 LSTTL loads |
| Package Type | SOIC (Small Outline Integrated Circuit) |
| Pin Count | 16 pins |
| Output Drive Capability | 25 mA (maximum) |
## Pin Configuration
The CD74HCT138M96 is housed in a 16-pin package, with the following pin configuration:
| Pin | Name | Description |
|---------|-------------|------------------------------------------|
| 1 | A0 | Input 0 |
| 2 | A1 | Input 1 |
| 3 | A2 | Input 2 |
| 4 | GND | Ground |
| 5 | /E1 | Enable Input 1 (active LOW) |
| 6 | /E2 | Enable Input 2 (active LOW) |
| 7 | /E3 | Enable Input 3 (active LOW) |
| 8 | Y0 | Output 0 (active LOW) |
| 9 | Y1 | Output 1 (active LOW) |
| 10 | Y2 | Output 2 (active LOW) |
| 11 | Y3 | Output 3 (active LOW) |
| 12 | Y4 | Output 4 (active LOW) |
| 13 | Y5 | Output 5 (active LOW) |
| 14 | Y6 | Output 6 (active LOW) |
| 15 | Y7 | Output 7 (active LOW) |
| 16 | Vcc | Supply Voltage |
## Applications
The CD74HCT138M96 is widely utilized in various applications, including:
1. Data Routing:
- Effectively routes data signals in digital circuits by selecting one of several data sources based on binary input values.
2. Memory Addressing:
- Can be used in memory address decoding where specific address lines are activated to access particular memory locations.
3. Microcontroller Interface:
- Often used in microcontroller systems for peripheral device selection and control.
4. LED Control:
- Useful in controlling multiple LEDs in applications where individual addressing is required.
5. Multiplexing/Demultiplexing:
- Functions efficiently as a demultiplexer, directing an input signal to one of several outputs based on control signals.
## Conclusion
The CD74HCT138M96 from Harris Corporation is a versatile and efficient 3-to-8 line decoder/demultiplexer offering high-speed performance coupled with low power consumption. Its wide range of applications and robust feature set make it an essential component in various digital electronics, enhancing functionality and efficiency in modern circuitry. For detailed implementation guidance and application notes, refer to the manufacturer’s datasheet and technical documents.
