74C74

74C74 Dual D-Type Flip-Flop Technical Summary

Overview

The MM74C74 is a dual D-type flip-flop constructed using complementary MOS (CMOS) technology, incorporating both N-channel and P-channel enhancement transistors. This integrated circuit features two independent flip-flops, each with dedicated data, preset, clear, and clock inputs, along with complementary Q and Q̅ outputs. The device operates by transferring the logic level present at the data input to the output upon the positive-going transition of the clock pulse. The preset and clear functions are asynchronous, meaning they operate independently of the clock signal and are activated by a low logic level.

Designed for versatility, the 74C74 is compatible with a wide range of supply voltages and offers performance characteristics that make it suitable for various digital applications, including those requiring TTL compatibility.

Features

• Wide Supply Voltage Range: Operates from 3V to 15V, making it suitable for both low-voltage and standard voltage applications.
• Low Power Consumption: CMOS technology ensures minimal power dissipation, ideal for battery-operated devices.
• High Noise Immunity: Typical of CMOS devices, the 74C74 offers excellent noise immunity, ensuring reliable operation in electrically noisy environments.
• TTL Compatibility: Can interface directly with TTL logic families, providing seamless integration into existing systems.
• Independent Preset and Clear Inputs: Each flip-flop features asynchronous preset and clear inputs for immediate control over the output state.
• Dual Flip-Flops: Contains two independent D-type flip-flops in a single package, saving board space and reducing component count.
• Positive Edge-Triggered Clocking: Data is transferred to the output on the rising edge of the clock signal, ensuring precise timing control.

Applications

The 74C74 is widely used in digital systems where reliable data storage and transfer are required. Common applications include:

• Data Storage and Transfer: Used in registers, shift registers, and memory elements for temporary data storage.
• Frequency Division: Employed in counters and dividers to reduce clock frequencies by integer factors.
• Synchronization: Helps synchronize asynchronous signals to a clock domain, preventing metastability issues.
• State Machines: Forms the basic building block for sequential logic circuits, such as finite state machines.
• Debouncing Circuits: Used to eliminate switch bounce in mechanical switches, ensuring clean digital signals.
• Interface Circuits: Acts as a buffer or level shifter between different logic families, such as TTL and CMOS.

Electrical Characteristics

The following table summarizes the key electrical specifications of the 74C74 under typical operating conditions (V_DD = 5V, T_A = 25°C):

• Supply Voltage Range (V_DD): 3V to 15V
• Input High Voltage (V_IH): 3.5V (min) at V_DD = 5V
• Input Low Voltage (V_IL): 1.5V (max) at V_DD = 5V
• Output High Voltage (V_OH): 4.95V (min) at I_OH = -0.4mA
• Output Low Voltage (V_OL): 0.05V (max) at I_OL = 0.4mA
• Propagation Delay (t_PD): 60ns (max) from clock to Q output
• Setup Time (t_SU): 25ns (min) before clock rising edge
• Hold Time (t_H): 5ns (min) after clock rising edge
• Power Dissipation (P_D): 10µW (typical) per flip-flop at 100kHz

Package Information

The 74C74 is available in multiple package options to accommodate different assembly and space requirements. The most common packages include:

• 14-Pin Plastic Dual In-Line Package (PDIP):
  • Package Code: N
  • Dimensions: 19.3mm x 6.35mm x 4.57mm
  • Pin Pitch: 2.54mm
• 14-Pin Small Outline Integrated Circuit (SOIC):
  • Package Code: D
  • Dimensions: 8.65mm x 3.9mm x 1.5mm
  • Pin Pitch: 1.27mm
• 14-Pin Thin Shrink Small Outline Package (TSSOP):
  • Package Code: PW
  • Dimensions: 5mm x 4.4mm x 1.1mm
  • Pin Pitch: 0.65mm

Pin Configuration

The pinout for the 74C74 is as follows (top view):

• Pin 1: Clear (CLR) for Flip-Flop 1 (Active Low)
• Pin 2: Data (D) Input for Flip-Flop 1
• Pin 3: Clock (CLK) Input for Flip-Flop 1
• Pin 4: Preset (PRE) for Flip-Flop 1 (Active Low)
• Pin 5: Q Output for Flip-Flop 1
• Pin 6: Q̅ Output for Flip-Flop 1
• Pin 7: Ground (GND)
• Pin 8: Q̅ Output for Flip-Flop 2
• Pin 9: Q Output for Flip-Flop 2
• Pin 10: Preset (PRE) for Flip-Flop 2 (Active Low)
• Pin 11: Clock (CLK) Input for Flip-Flop 2
• Pin 12: Data (D) Input for Flip-Flop 2
• Pin 13: Clear (CLR) for Flip-Flop 2 (Active Low)
• Pin 14: Supply Voltage (V_DD)

Functional Description

The 74C74 operates as a positive-edge-triggered D-type flip-flop. When the clock input receives a rising edge, the logic level present at the D input is transferred to the Q output, while the Q̅ output assumes the complementary state. The preset (PRE) and clear (CLR) inputs, when activated (low), override the clock and data inputs, setting the Q output high or low, respectively. These inputs are asynchronous and do not require a clock pulse to take effect.

The device is designed to ensure reliable operation across its specified voltage range, with built-in protection against static discharge and latch-up, common concerns in CMOS devices.

Conclusion

The 74C74 dual D-type flip-flop is a versatile and reliable component for digital systems, offering a combination of low power consumption, high noise immunity, and TTL compatibility. Its independent preset and clear functions, along with positive-edge triggering, make it