7474 Dual D-Type Positive-Edge-Triggered Flip-Flop with Preset and Clear

Overview

The 7474 is a dual D-type flip-flop integrated circuit featuring independent data, clock, set, and reset inputs for each flip-flop. This device is constructed with high-speed silicon-gate CMOS technology and provides the edge-triggered D-type flip-flop functionality with asynchronous clear and preset capabilities. The 7474 is widely used in digital systems for data storage, synchronization, and transfer applications.

Each flip-flop in the 7474 features direct asynchronous inputs (PRESET and CLEAR) that are independent of the clock. Data is transferred from the D input to the output on the positive-going edge of the clock pulse. The outputs include both true (Q) and complement (Q) signals for flexible system design.

Features

• Dual D-type positive-edge-triggered flip-flops with independent inputs
• Asynchronous set (PRESET) and reset (CLEAR) for each flip-flop
• Standard symmetrical output characteristics
• High noise immunity typical of CMOS devices
• Low power consumption: 20μA maximum ICC
• Wide operating voltage range: 2V to 6V
• High-speed operation: 50MHz typical clock frequency at 5V
• Balanced propagation delays
• Direct interface with TTL levels (with appropriate supply voltage)
• Available in multiple package options including PDIP, SOIC, and TSSOP

Applications

• Data storage and transfer in digital systems
• Buffer registers
• Shift registers
• Pattern generators
• Control circuits
• Frequency division
• Synchronization circuits
• General digital logic applications

Pin Configuration and Description

Pinout Diagram

[Visual representation of pinout would be inserted here in actual documentation]

Detailed Pin Description

• Pin 1, 13 (1CLR, 2CLR): Asynchronous Reset (active LOW) for each flip-flop
• Pin 2, 12 (1D, 2D): Data inputs for each flip-flop
• Pin 3, 11 (1CK, 2CK): Clock inputs (positive-edge triggered)
• Pin 4, 10 (1PR, 2PR): Asynchronous Preset (active LOW) for each flip-flop
• Pin 5, 9 (1Q, 2Q): True outputs for each flip-flop
• Pin 6, 8 (1Q, 2Q): Complementary outputs for each flip-flop
• Pin 7 (GND): Ground reference (0V)
• Pin 14 (VCC): Positive power supply (2V to 6V)

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (VCC): -0.5V to +7V
• Input Voltage (VI): -0.5V to VCC + 0.5V
• Output Voltage (VO): -0.5V to VCC + 0.5V
• Input Diode Current (IIK): ±20mA
• Output Diode Current (IOK): ±20mA
• Output Current (IO): ±25mA
• Supply Current (ICC): ±50mA
• Power Dissipation (PD): 500mW
• Storage Temperature Range (TSTG): -65°C to +150°C

Recommended Operating Conditions

Functional Description

Truth Table

Note: X = Don't Care, ↑ = LOW-to-HIGH transition

Timing Characteristics

Typical propagation delay times (VCC = 5V, TA = 25°C):

• Clock to Q: 13ns
• Preset to Q: 14ns
• Clear to Q: 14ns
• Setup Time (D to Clock): 10ns
• Hold Time (D after Clock): 3ns
• Maximum Clock Frequency: 50MHz

Package Information

Available Packages

• PDIP-14: Plastic Dual In-Line Package, 14 pins
• SOIC-14: Small Outline Integrated Circuit, 14 pins
• TSSOP-14: Thin Shrink Small Outline Package, 14 pins

Package Dimensions (PDIP-14)

• Body Length: 19.30mm (max)
• Body Width: 6.35mm (max)
• Lead Pitch: 2.54mm
• Package Height: 4.57mm (max)

Design Considerations

Power Supply Decoupling

A 0.1μF ceramic capacitor should be connected between VCC and GND, placed as close to the IC as possible to minimize noise and ensure stable operation.

Unused Inputs

All unused inputs should be tied to either VCC or GND through a resistor (typically 1kΩ to 10kΩ) to prevent floating input conditions that could lead to excessive power consumption or erratic operation.

Clock Signal Quality

For reliable operation, clock signals should have fast rise and fall times (typically < 100ns). Slow transitions may cause metastability or improper triggering.

Conclusion

The 7474