onsemi MC74ACT14DR2G Hex Inverting Schmitt Trigger: Datasheet, Pinout, and Application Circuit Guide

The MC74ACT14DR2G from onsemi is a highly versatile and widely used integrated circuit belonging to the ACT advanced CMOS logic family. This device features six independent inverting Schmitt-trigger gates in a single compact package. The defining characteristic of a Schmitt trigger is its hysteresis voltage, which allows it to effectively clean up noisy signals and convert slow-moving input waveforms into sharp, well-defined digital outputs. This makes it an indispensable component for signal conditioning in a vast array of digital systems.

Datasheet Overview and Key Specifications

Understanding the datasheet is crucial for proper implementation. The MC74ACT14DR2G is designed for high-speed operation while maintaining low power consumption, typical of the ACT family which offers TTL-compatible inputs.

Key electrical characteristics include:

Supply Voltage Range (VCC): 4.5V to 5.5V (standard 5V operation).

High-Level Input Voltage (VIH): Minimum 2.0V.

Low-Level Input Voltage (VIL): Maximum 0.8V.

Hysteresis (ΔVT): Typically 1.0V at 5.0V VCC. This is the voltage difference between the positive-going (VT+) and negative-going (VT-) thresholds, which is the core of its noise immunity.

Propagation Delay (tPD): Very fast, typically 7.5ns at 5V, making it suitable for high-frequency applications.

Package: The "DR2G" suffix denotes a SOIC-14 surface-mount package, which is common for automated PCB assembly.

Pinout Configuration

The MC74ACT14DR2G comes in a 14-pin package. The pinout is standard for a Hex Inverter configuration:

Pins 1A to 6A: These are the inputs for the six individual Schmitt-trigger inverters.

Pins 1Y to 6Y: These are the corresponding outputs for each inverter.

Pin 7 (GND): Ground (0V reference).

Pin 14 (VCC): Positive supply voltage (typically +5V).

Application Circuit Guide

The primary function of the MC74ACT14 is to condition digital signals. Here are two fundamental application circuits:

1. Signal Debouncing (Switch Input):

A classic use case is debouncing a mechanical push button or switch. Without a Schmitt trigger, the mechanical chatter of a switch can be interpreted by a microcontroller as multiple rapid presses.

Circuit: Connect one side of the switch to VCC (5V). Connect the other side to ground through a pull-down resistor (e.g., 10kΩ). The node between the switch and the resistor is connected to the input of one MC74ACT14 inverter. The output of the inverter provides a clean, bounce-free inverted signal to the microcontroller's input pin. The hysteresis ensures that the noisy, slow transition during contact bounce is ignored, resulting in a single, clean logic transition.

2. Waveform Shaping (Oscillator / Pulse Generator):

The Schmitt trigger can be used to create a simple RC oscillator, converting a DC voltage into a square wave.

Circuit: Connect the output (e.g., 1Y) of an inverter back to its input (1A) through a resistor (R1). Place a capacitor (C1) from the input (1A) to ground. The values of R1 and C1 determine the oscillation frequency (f ≈ 0.8 / (R1 C1)). This circuit is excellent for generating clock signals or timing pulses where precise frequency is not critical. The remaining five inverters on the chip can be used for other tasks.

ICGOOODFIND

The onsemi MC74ACT14DR2G is an essential component for any digital designer's toolkit. Its robust signal conditioning capabilities, provided by its built-in hysteresis, make it perfect for cleaning up noisy inputs from sensors and switches, creating simple oscillators, and ensuring reliable data transmission in electrically noisy environments. Its high speed and hex configuration offer excellent functionality and value in a single, small-footprint IC.

Keywords:

Schmitt Trigger

Signal Conditioning

Hysteresis

Hex Inverter

Waveform Shaping