Quad 2-Input Non-Inverting Multiplexers with 3-State Outputs# CD74AC257M96 Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The CD74AC257M96 is a quad 2-input multiplexer with 3-state outputs, primarily used for data routing and selection in digital systems. Key applications include:
- Data Bus Multiplexing : Routes multiple data sources to a common bus
- Memory Address Selection : Selects between different address sources in memory systems
- I/O Port Expansion : Expands microcontroller I/O capabilities through multiplexing
- Signal Routing : Directs analog or digital signals to different processing paths
- Test Equipment : Used in automated test systems for signal switching
### Industry Applications
- Automotive Electronics : Instrument clusters, infotainment systems
- Industrial Control : PLC systems, motor control units
- Telecommunications : Switching equipment, network routers
- Consumer Electronics : Smart home devices, audio/video systems
- Medical Devices : Patient monitoring equipment, diagnostic instruments
### Practical Advantages
- High-Speed Operation : Typical propagation delay of 7.5 ns at 5V
- Low Power Consumption : 4μA maximum ICC at 25°C
- Wide Operating Voltage : 2V to 6V supply range
- 3-State Outputs : Allows bus-oriented applications
- High Noise Immunity : Characteristic of AC logic family
### Limitations
- Limited Drive Capability : Maximum output current of 24mA
- ESD Sensitivity : Requires proper handling procedures
- Temperature Range : Commercial grade (0°C to 70°C)
- Package Constraints : SOIC-16 package limits power dissipation
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Output Bus Contention
- Issue : Multiple enabled outputs driving the same bus
- Solution : Implement proper output enable control sequencing
Pitfall 2: Power Supply Decoupling
- Issue : Inadequate decoupling causing signal integrity problems
- Solution : Use 100nF ceramic capacitor close to VCC pin
Pitfall 3: Unused Input Handling
- Issue : Floating inputs causing unpredictable behavior
- Solution : Tie unused inputs to VCC or GND through pull-up/down resistors
### Compatibility Issues
Voltage Level Compatibility
- TTL Interfaces : Direct compatibility with 5V TTL levels
- CMOS Interfaces : Compatible with 3.3V and 5V CMOS
- Mixed Voltage Systems : Requires level shifting when interfacing with lower voltage devices
Timing Considerations
- Setup/Hold Times : Ensure proper timing margins with clocked systems
- Propagation Delay : Account for 5-10 ns delay in critical timing paths
### PCB Layout Recommendations
Power Distribution
- Use star-point grounding for analog and digital sections
- Implement separate power planes for clean and noisy circuits
- Place decoupling capacitors within 5mm of power pins
Signal Routing
- Keep high-speed signals away from clock lines
- Use 45° angles instead of 90° for trace bends
- Maintain consistent impedance for critical signal paths
Thermal Management
- Provide adequate copper pour for heat dissipation
- Ensure proper ventilation in high-density layouts
- Consider thermal vias for improved heat transfer
## 3. Technical Specifications
### Key Parameters
| Parameter | Value | Conditions |
|-----------|-------|------------|
| Supply Voltage | 2.0V to 6.0V | - |
| High-Level Input Voltage | 2.1V min | VCC = 4.5V |
| Low-Level Input Voltage | 0.9V max | VCC = 4.5V |
| Propagation Delay | 7.
