What is Controlled Impedance and How it Important in PCB
Controlled Impedance boards have been manufactured since the early 80s but with the increase in the sophistication of modern electronics, the requirement of precision manufacturing with tight tolerance has increased. The impedance value of a PCB is dependent on many variables. In order of their significant impact on impedance, these variables include the thickness of the substrate, dielectric constant, conductor width and copper thickness. High-frequency circuit materials are formulated to have a tight thickness control as well as dielectric constant control. Printed circuit boards with impedance necessities will switch the adjustments in voltage happening and prompt an electrical gadget or contraption that works of course. The utilization of differential impedance PCB parts gives the control expected to a scope of items. Controlled Impedance PCBs are becoming common nowadays due to the increase in the demand for high-speed Video, USB Interface, Ethernet interface, and wireless communications.
The importance of controlled impedance hinges upon many variables, such as the PCB’s characteristics and how it is to be used. A PCB designed for digital applications will often have different impedance requirements than a circuit designed for RF applications. Within both of these categories, however, there are sub-categories of specific types of applications. Digital applications, especially high-speed digital applications, will require consistent and controlled impedance values for signal integrity purposes. There are many different methods for checking a PCB for good signal integrity: eye diagrams, pulse distortion, bit error rate, and skew. A critical trace on a digital board with impedance variation can impact these quality measurements of the PCB.
There are several different types of impedance. The most common type of Controlled Impedance on a PCB is referred to as characteristic impedance. Other types include input impedance, wave impedance, image impedance, and others. Many of the impedance issues are frequency-dependent, and this can be an issue for wideband power amplifiers. The impedance matching network that is necessary for the design of a power amplifier can only tune the impedance transitions over a range of frequencies. Many times the actual power amplifier IC can be used over a wider range of frequencies than the tuning networks that are used to match the impedance for traces going into and out of the chip.