Overview
The SN74HC148D is an 8-line to 3-line priority encoder produced by Texas Instruments. This device is part of the HC series, known for its high-speed CMOS logic. It features priority decoding of the inputs, ensuring that only the highest-order data line is encoded. The SN74HC148D is designed to encode eight data lines into a 3-line (4-2-1) binary (octal) output. It includes input enable (EI) and output enable (EO) signals, which facilitate cascading multiple stages without the need for external circuitry.
Key Specifications
| Parameter | Min | Max | Unit | |
|---|---|---|---|---|
| VCC Supply Voltage | 2 | 5 | 6 | V |
| VIH High-Level Input Voltage | 1.5 (VCC=2V), 3.15 (VCC=4.5V), 4.2 (VCC=6V) | V | ||
| VIL Low-Level Input Voltage | 0.5 (VCC=2V), 1.35 (VCC=4.5V), 1.8 (VCC=6V) | V | ||
| IOH High-Level Output Current | -20 μA, -4 mA, -5.2 mA | A | ||
| IOL Low-Level Output Current | 20 μA, 4 mA, 5.2 mA | A | ||
| tpd Propagation Delay | 16 ns (VCC=2V), 23 ns (VCC=4.5V), 21 ns (VCC=6V) | ns | ||
| TJ Junction Temperature | -55 to 150 | °C | ||
| ICC Supply Current | 8 μA (VCC=2V), 80 μA (VCC=6V) | μA |
Key Features
- Wide operating voltage range of 2V to 6V
- Outputs can drive up to 10 LSTTL loads
- Low power consumption, with a maximum ICC of 80 μA at 6V
- Typical propagation delay of 16 ns at VCC = 2V
- ±4-mA output drive at 5V
- Low input current of 1 μA max
- Encode eight data lines to 3-line binary (octal)
- Input enable (EI) and output enable (EO) signals for cascading
Applications
- N-Bit encoding
- Code converters and generators
- Prioritization in digital systems where multiple inputs need to be encoded into a smaller binary representation
- Cascading encoders for larger input sets
Q & A
- What is the primary function of the SN74HC148D?
The SN74HC148D is an 8-line to 3-line priority encoder, which encodes eight data lines into a 3-line binary (octal) output, prioritizing the highest-order data line.
- What is the operating voltage range of the SN74HC148D?
The operating voltage range is from 2V to 6V.
- How many LSTTL loads can the outputs of the SN74HC148D drive?
The outputs can drive up to 10 LSTTL loads.
- What is the typical propagation delay of the SN74HC148D at VCC = 2V?
The typical propagation delay is 16 ns at VCC = 2V.
- What are the input enable (EI) and output enable (EO) signals used for?
The EI and EO signals are used for cascading multiple stages without the need for external circuitry.
- What is the maximum supply current (ICC) of the SN74HC148D at VCC = 6V?
The maximum supply current is 80 μA at VCC = 6V.
- What is the junction temperature range of the SN74HC148D?
The junction temperature range is from -55°C to 150°C.
- Can the SN74HC148D be used in safety-critical applications?
No, it is not recommended for use in safety-critical applications without proper evaluation and validation.
- What are some common applications of the SN74HC148D?
Common applications include N-Bit encoding, code converters, and generators, as well as prioritization in digital systems.
- How should unused inputs of the SN74HC148D be handled?
Unused inputs must be held at VCC or GND to ensure proper device operation.
