7405 Hex Inverter with Open-Collector Outputs

Overview

The 7405 is a hex inverter integrated circuit belonging to the 7400 series of TTL logic devices. This component features six independent inverter gates with open-collector outputs, making it particularly useful for applications requiring wired-AND functionality or interfacing with higher voltage circuits. The open-collector outputs allow the device to sink current but not source it, requiring pull-up resistors for proper operation in most applications.

As part of the standard TTL family, the 7405 operates with a nominal 5V power supply and provides standard TTL logic levels. The device is packaged in a 14-pin DIP (Dual In-line Package) format, which was the industry standard for through-hole mounting during its peak popularity.

Features

• Six independent inverter gates in single package
• Open-collector outputs for wired-AND applications
• Standard TTL switching voltages
• 14-pin DIP package for easy prototyping and through-hole mounting
• Wide operating temperature range (typically 0°C to 70°C commercial grade)
• Compatible with most TTL and 5V CMOS logic families
• Outputs can sink up to 16mA (typical)
• High noise immunity characteristic of TTL devices

Applications

The 7405 finds use in numerous digital logic applications, particularly where open-collector outputs are beneficial:

• Logic level inversion
• Wired-AND logic configurations
• Bus driver applications
• Interfacing with higher voltage circuits (with appropriate pull-up resistors)
• LED driving circuits
• Relay or solenoid drivers
• General purpose digital logic circuits
• Signal conditioning circuits
• Debouncing switch inputs

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (V_CC): -0.5V to +7V
• DC Input Voltage (V_I): -0.5V to V_CC + 0.5V
• DC Output Voltage (V_O): -0.5V to V_CC + 0.5V
• DC Input Diode Current (I_IK): ±20mA
• Operating Temperature Range: 0°C to 70°C (commercial grade)
• Storage Temperature Range: -65°C to 150°C

Recommended Operating Conditions

• Supply Voltage (V_CC): 4.75V to 5.25V
• High-Level Input Voltage (V_IH): 2V min
• Low-Level Input Voltage (V_IL): 0.8V max
• Operating Free-Air Temperature: 0°C to 70°C

DC Characteristics

• High-Level Output Current (I_OH): -400μA max
• Low-Level Output Current (I_OL): 16mA max
• Input Clamp Voltage (V_IK): -1.5V max at I_IK = -18mA
• High-Level Input Current (I_IH): 40μA max at V_IH = 2.7V
• Low-Level Input Current (I_IL): -1.6mA max at V_IL = 0.4V

AC Characteristics

• Propagation Delay Time (t_PLH, t_PHL): 22ns max (typical 15ns)
• Output Transition Time (t_TLH, t_THL): 15ns max

Package Information

14-Pin DIP (Dual In-line Package)

• Package Type: PDIP (Plastic Dual In-line Package)
• Pin Count: 14
• Row Spacing: 300 mil (7.62mm)
• Pin Spacing: 100 mil (2.54mm) between adjacent pins
• Package Width: 6.35mm max
• Package Length: 19.3mm max
• Lead Material: Copper alloy
• Lead Finish: Solder-plated or tin-plated

Pin Configuration

• Pin 1: 1A (Input for Gate 1)
• Pin 2: 1Y (Output for Gate 1)
• Pin 3: 2A (Input for Gate 2)
• Pin 4: 2Y (Output for Gate 2)
• Pin 5: 3A (Input for Gate 3)
• Pin 6: 3Y (Output for Gate 3)
• Pin 7: GND (Ground)
• Pin 8: 4Y (Output for Gate 4)
• Pin 9: 4A (Input for Gate 4)
• Pin 10: 5Y (Output for Gate 5)
• Pin 11: 5A (Input for Gate 5)
• Pin 12: 6Y (Output for Gate 6)
• Pin 13: 6A (Input for Gate 6)
• Pin 14: V_CC (Positive Supply Voltage)

Functional Description

The 7405 performs the logical inversion (NOT) function. Each of the six gates follows the truth table where a high input (H) produces a low output (L), and a low input (L) produces a high-impedance output (Z). The open-collector outputs require external pull-up resistors to provide the high logic level when the output transistor is off.

The electrical characteristics of the 7405 are typical of standard TTL devices, with a nominal supply voltage of 5V. The device exhibits the standard TTL input characteristics, including input clamping diodes that help limit input voltage excursions.

Design Considerations

When using the 7405 in circuit designs, several important factors should be considered:

• Pull-up Resistors: The open-collector outputs require pull-up resistors to provide the high logic level. The resistor value must be chosen based on the desired speed and power consumption.
• Power Supply Decoupling: Like all TTL devices, proper decoupling with 0.1μF capacitors near the power pins is recommended.
• Fan-out: The 7405 can typically drive 10 standard TTL inputs while maintaining proper logic levels.
• Wired-AND Configuration: Multiple open-collector outputs can be tied together with a single pull-up resistor to create a wired-AND function.
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