Programmable Logic Devices in Digital Electronics: An Overview
by Yuvi K - December 16, 2023
What is Programmable Logic Device?
Programmable logic devices (PLDs) are digital semiconductor circuits created to be re-programmed according to user’s needs. PLDs are often used as cost-effective replacements for dedicated logic chips, allowing a variety of logic functions to be implemented in a single chip. They are widely used in the consumer electronics industry, where they are known as logic chips, because they are available in both integrated circuit (IC) and Printed Circuit Board (PCB) formats.
PLDs are used in a variety of applications, including digital logic, control systems, and data acquisition. Some examples include the memory devices used in computers, the digital signal processors (DSPs) used in telecommunications, the controllers used in industrial automation, and the sensors used in automotive systems.
In order to better understand the function of the PLDs, it is important to first understand the basic circuit components and their roles in digital circuitry.
Circuit Components
The basic components of a digital circuit include transistors, resistors, capacitors, diodes, and logic gates. Transistors control the current flow between two points by acting as a switch. Resistors act as a current-limiting device, and capacitors store energy within a circuit. Diodes create a voltage drop in a circuit, allowing certain components to remain “on” when the other components are “off”.
Logic gates are the core components of digital circuitry, and they are used to perform certain logic functions. The most basic logic gates are AND, OR, NOT, and NAND.
The AND gate performs a logical AND operation between two inputs, which means that if both inputs are “on”, then the output is “on” as well. The OR gate performs a logical OR operation between two inputs, which means that if either of the two inputs is “on”, then the output is “on” as well.
The NOT gate performs a logical NOT operation between two inputs, which means that if the input is “on”, then the output is “off”. The NAND gate performs a logical NAND operation between two inputs, which means that if either of the two inputs is “off”, then the output is “off” as well.
Programmable Logic Devices
Programmable logic devices (PLDs) are semiconductor devices that are programmed by the user to perform specific logic functions. PLDs are used in a variety of applications, including digital logic, control systems, data acquisition, and memory devices.
The most popular PLDs are the Complex Programmable Logic Devices (CPLDs), the Field Programmable Gate Arrays (FPGAs), and the Programmable Array Logic (PALs).
Complex Programmable Logic Devices (CPLDs)
A CPLD is a programmable logic device that contains a set of integrated logic elements that can be programmed to perform a specific logic function. CPLDs are characterized by their high density and low power consumption. CPLDs are typically used in applications such as consumer electronics, automated test equipment and control systems.
Field Programmable Gate Arrays (FPGAs)
A Field Programmable Gate Array (FPGA) is a large, very complex programmable logic device that contains thousands of logic elements and can be programmed to perform a wide range of functions. FPGAs are used for a variety of applications, including digital signal processing, high-speed communication, and data acquisition.
Programmable Array Logic (PALs)
A Programmable Array Logic (PAL) is a type of programmable logic device that contains a set of programmable logic elements that can be programmed to perform a specific logic function. PALs are typically used in applications such as data acquisition, signal processing, and control systems.
Conclusion
Programmable logic devices (PLDs) are a key component of modern digital circuitry. PLDs are used in a variety of applications, and they are becoming increasingly important as technology advances. The three most popular types of PLDs are Complex Programmable Logic Devices (CPLDs), Field Programmable Gate Arrays (FPGAs), and Programmable Array Logic (PALs).
PLDs provide the flexibility needed to create complex digital circuits, and are becoming an essential tool for the design and implementation of digital systems. As technology continues to advance, PLDs are likely to become even more important for circuit design.
