Octal D-Type Flip-Flops with 3-State Outputs# CD74ACT374E Octal D-Type Flip-Flop with 3-State Outputs
*Manufacturer: HARRIS*
## 1. Application Scenarios
### Typical Use Cases
The CD74ACT374E serves as an 8-bit transparent latch with 3-state outputs , making it ideal for:
- Data bus buffering and isolation in microprocessor systems
- Temporary data storage between asynchronous systems
- Input/output port expansion for microcontroller interfaces
- Pipeline registers in digital signal processing applications
- Bus-oriented systems requiring multiple drivers on a single bus
### Industry Applications
- Industrial Control Systems : Interface between sensors and control processors
- Automotive Electronics : ECU communication buses and sensor data aggregation
- Telecommunications : Data routing and temporary storage in switching systems
- Consumer Electronics : Memory address latching and display driver interfaces
- Medical Devices : Patient monitoring system data acquisition
### Practical Advantages
- High-speed operation with typical propagation delay of 8.5ns at 5V
- 3-state outputs enable bus sharing and reduce system component count
- Wide operating voltage range (4.5V to 5.5V) compatible with TTL levels
- High noise immunity characteristic of ACT logic family
- Low power consumption compared to bipolar equivalents
### Limitations
- Limited drive capability (24mA output current) may require buffers for heavy loads
- Single supply operation restricts use in mixed-voltage systems
- No internal pull-up/pull-down resistors require external components for floating inputs
- Temperature range (military grade: -55°C to 125°C) may be over-specified for commercial applications
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Clock Signal Integrity
- Pitfall : Excessive clock skew causing metastability
- Solution : Implement proper clock distribution networks with matched trace lengths
Output Enable Timing
- Pitfall : Bus contention during output enable/disable transitions
- Solution : Ensure output enable signals change when clock is inactive
Power Supply Decoupling
- Pitfall : Inadequate decoupling causing signal integrity issues
- Solution : Place 0.1μF ceramic capacitors within 0.5cm of VCC and GND pins
### Compatibility Issues
Voltage Level Compatibility
- TTL Compatibility : Direct interface with TTL devices without level shifters
- CMOS Compatibility : Requires attention to input threshold levels (1.5V VIH min)
- Mixed 3.3V/5V Systems : May require level translation for proper operation
Timing Constraints
- Setup time: 4.5ns minimum
- Hold time: 0ns minimum
- Clock pulse width: 5ns minimum
### PCB Layout Recommendations
Power Distribution
- Use dedicated power and ground planes
- Implement star-point grounding for mixed-signal systems
- Ensure low-impedance power paths to all VCC pins
Signal Routing
- Keep clock signals away from high-speed data lines
- Route output enable signals with similar care as clock signals
- Maintain consistent characteristic impedance for bus lines
Thermal Management
- Provide adequate copper area for heat dissipation
- Consider thermal vias for high-frequency operation
- Ensure proper airflow in high-density layouts
## 3. Technical Specifications
### Key Parameter Explanations
DC Characteristics
- VOH (Output High Voltage) : Minimum 4.4V at IOH = -24mA
- VOL (Output Low Voltage) : Maximum 0.55V at IOL = 24mA
- II (Input Current) : ±1μA maximum at VCC = 5.5V
- ICC
