Overview
The SN74HC157DR, produced by Texas Instruments, is a quadruple 2-line to 1-line data selector/multiplexer. This device is part of the 74HC series, known for its high-speed silicon gate CMOS technology. It is designed to select one of two data sources for each of its four channels, making it an excellent choice for multiplexing and data routing applications. The device operates asynchronously, with each output being controlled by the same address select (A/B) and strobe (G) inputs. A high level at the strobe terminal forces all outputs low, regardless of the state of other inputs.
Key Specifications
| Parameter | Unit | Min | 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) |
| ICC (Supply Current) | μA | 8 | 160 | 160 |
| tpd (Propagation Delay) | ns | 11 (VCC=6V) | 25 (VCC=4.5V) | 63 (VCC=2V) |
| IOH (Output Current High) | mA | -6 | -7.8 | |
| IOL (Output Current Low) | mA | 6 | 7.8 | |
| TA (Operating Free-Air Temperature) | °C | -55 | 125 |
Key Features
- Wide operating voltage range of 2V to 6V
- Outputs can drive up to 15 LSTTL loads
- Low power consumption, with a maximum ICC of 160 μA
- Typical propagation delay of 11ns at VCC = 6V
- ±6mA output drive at 5V
- Low input current of 1μA max
- Standard CMOS inputs with high impedance
- Schmitt-trigger inputs are not available in this model, but it has standard CMOS inputs
Applications
The SN74HC157DR is suitable for various applications including:
- Data selection and multiplexing in digital systems
- Data routing and switching in communication systems
- Control systems where multiple data sources need to be selected dynamically
- Embedded systems requiring low power consumption and high-speed data processing
Q & A
- What is the operating voltage range of the SN74HC157DR?
The operating voltage range is from 2V to 6V.
- How many data selectors/multiplexers are included in the SN74HC157DR?
The device includes four 2-line to 1-line data selectors/multiplexers.
- What is the typical propagation delay of the SN74HC157DR at VCC = 6V?
The typical propagation delay is 11ns at VCC = 6V.
- What is the maximum output current drive at 5V?
The maximum output current drive is ±6mA at 5V.
- How does the strobe input affect the outputs of the SN74HC157DR?
A high level at the strobe terminal forces all outputs low, regardless of the state of other inputs.
- What is the recommended bypass capacitor for the power supply?
A 0.1μF bypass capacitor is recommended, and using multiple bypass capacitors in parallel can help reject different frequencies of noise.
- What are the key considerations for the layout of the SN74HC157DR on a PCB?
Key considerations include placing bypass capacitors near the positive supply terminal, providing a short ground return path, using wide traces to minimize impedance, and keeping the device, capacitors, and traces on the same side of the board whenever possible.
- Can the SN74HC157DR drive a load with a total capacitance greater than 50 pF?
While the device can drive a load with a total capacitance less than or equal to 50 pF, larger capacitive loads can be applied but are not recommended to exceed 50 pF.
- What is the maximum junction temperature for the SN74HC157DR?
The maximum junction temperature is 125°C.
- What are the typical applications of the SN74HC157DR?
Typical applications include data selection, multiplexing, and data routing in digital and communication systems.
