Dual Positive-Edge-Triggered D-Type Flip-Flops with Set and Reset# CD74AC74 Dual D-Type Positive-Edge-Triggered Flip-Flop Technical Documentation
*Manufacturer: HARRIS*
## 1. Application Scenarios
### Typical Use Cases
The CD74AC74 is a dual D-type flip-flop with direct clear and preset inputs, making it suitable for various digital logic applications:
Data Storage and Transfer
- Temporary data storage in microprocessor systems
- Pipeline registers for data synchronization
- Shift register configurations when cascaded
- Data bus interfacing and buffering
Timing and Control Circuits
- Frequency division (divide-by-2, 4, 8, etc.)
- Clock synchronization circuits
- Pulse shaping and waveform generation
- Event sequencing and timing control
State Machine Implementation
- Sequential logic circuits
- Finite state machine design
- Control logic for digital systems
- Counter and timer circuits
### Industry Applications
Consumer Electronics
- Digital televisions and set-top boxes
- Audio/video processing equipment
- Gaming consoles and peripherals
- Smart home automation systems
Computing Systems
- Memory address registers
- I/O port control circuits
- Bus interface logic
- Peripheral control units
Industrial Automation
- Process control systems
- Motor control circuits
- Sensor data acquisition
- Programmable logic controller (PLC) interfaces
Communications Equipment
- Data transmission systems
- Modem and router logic
- Signal processing circuits
- Protocol implementation logic
### Practical Advantages and Limitations
Advantages:
- High-Speed Operation : Typical propagation delay of 8.5 ns at 5V
- Low Power Consumption : CMOS technology ensures minimal static power
- Wide Operating Voltage : 2V to 6V supply range
- High Noise Immunity : 0.5VCC noise margin typical
- Symmetric Output Drive : Balanced source/sink capability
- Direct Set/Reset : Asynchronous preset and clear functions
Limitations:
- Limited Drive Capability : Maximum output current of 24mA
- ESD Sensitivity : Requires proper handling procedures
- Temperature Constraints : Operating range -55°C to +125°C
- Power Supply Sensitivity : Requires stable, well-regulated power
- Clock Edge Requirements : Strict setup and hold time compliance
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Timing Violations
- Pitfall : Inadequate setup/hold time margins causing metastability
- Solution : Ensure minimum 5 ns setup time and 0 ns hold time at 5V
- Implementation : Use proper clock distribution and buffer circuits
Power Supply Issues
- Pitfall : Voltage spikes and noise affecting reliability
- Solution : Implement decoupling capacitors (100nF ceramic close to VCC)
- Implementation : Use separate power planes and proper grounding
Signal Integrity Problems
- Pitfall : Ringing and overshoot on high-speed signals
- Solution : Implement series termination resistors (22-100Ω)
- Implementation : Control trace impedance and minimize stubs
### Compatibility Issues with Other Components
Mixed Logic Families
- TTL Compatibility : Direct interface with TTL inputs possible
- CMOS Compatibility : Excellent with other AC/ACT series devices
- Level Shifting Required : When interfacing with 3.3V or lower voltage devices
- Drive Capability : May require buffers when driving multiple loads
Clock Distribution
- Clock Source Compatibility : Works with crystal oscillators and clock generators
- Fan-out Limitations : Maximum of 50 AC inputs per output
- Timing Alignment : Consider propagation delays in clock distribution networks
### PCB Layout Recommendations
Power Distribution
- Place 100nF decoupling capacitor within 5mm of each VCC pin
- Use
