Overview
The SN74HC148DG4 is an 8-line to 3-line priority encoder produced by Texas Instruments. This device is part of the 74HC series, known for its high-speed CMOS logic. The SN74HC148 is designed to encode eight data lines into a 3-line binary (octal) output, making it useful in various digital encoding and decoding applications. The device includes input enable (EI) and output enable (EO) signals, which facilitate cascading multiple stages without the need for additional external circuitry.
Key Specifications
| Parameter | Unit | Min | Typ | Max |
|---|---|---|---|---|
| VCC Supply Voltage | V | 2 | 5 | 6 |
| VIH High-Level Input Voltage | V | 1.5 (VCC=2V) | 3.15 (VCC=4.5V) | 4.2 (VCC=6V) |
| VIL Low-Level Input Voltage | V | 0.5 (VCC=2V) | 1.35 (VCC=4.5V) | 1.8 (VCC=6V) |
| VOH High-Level Output Voltage | V | 1.9 (IOH=-20μA) | 4.4 (IOH=-4mA) | 5.9 (IOH=-5.2mA) |
| VOL Low-Level Output Voltage | V | 0.1 (IOL=20μA) | 0.17 (IOL=4mA) | 0.26 (IOL=5.2mA) |
| ICC Supply Current | μA | 8 | 80 | 160 |
| tpd Propagation Delay | ns | 16 (VCC=2V) | 23 (VCC=4.5V) | 21 (VCC=6V) |
| TJ Junction Temperature | °C | - | - | 150 |
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
- 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
- Priority encoding in digital systems
- Cascaded encoding for larger input sets
Q & A
- What is the primary function of the SN74HC148?
The SN74HC148 is an 8-line to 3-line priority encoder, encoding eight data lines into a 3-line binary (octal) output.
- What is the operating voltage range of the SN74HC148?
The operating voltage range is from 2V to 6V.
- How many LSTTL loads can the outputs of the SN74HC148 drive?
The outputs can drive up to 10 LSTTL loads.
- What is the typical propagation delay of the SN74HC148 at VCC = 2V?
The typical propagation delay is 16 ns at VCC = 2V.
- What are the input enable and output enable signals used for?
The input enable (EI) and output enable (EO) signals allow for cascading multiple stages without additional external circuitry.
- What is the maximum junction temperature for the SN74HC148?
The maximum junction temperature is 150°C.
- What are some common applications of the SN74HC148?
Common applications include N-Bit encoding, code converters and generators, and priority encoding in digital systems.
- How does the SN74HC148 handle input transients?
The device must consider wrong addresses during input transients and transient lows on GS when all inputs are high.
- What type of packages is the SN74HC148 available in?
The SN74HC148 is available in various packages including SOIC, PDIP, SO, and LCCC.
- What is the recommended power supply bypass capacitor for the SN74HC148?
A 0.1-μF capacitor is recommended to prevent power disturbances.
