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Miniaturization is a hot trend in the PCB industry. There is a huge demand for compact sized and fast-paced PCBs. Although an asset in many electronic devices, there are many components in these fast PCBs, which may not work as expected, and lead to failure. Hence, the PCB manufacturers know the importance of slowing down certain circuits to enable the specific functioning of components. This is where controlled impedance can help. What is a controlled impedance? What is the importance of this factor? What are the determining factors of controlled impedance? Where is the controlled impedance used? Are these questions conjuring your mind? If yes, this post will help you find answers to all your questions.
To understand controlled impedance, it is important that you understand impedance. Impedance is only defined for high-frequency circuits. It is a combination of inductance and capacitance of the circuit. The value of impedance always varies between the two points, if not controlled properly. At high frequencies, PCB traces do not behave as expected, and the quality of signals may degrade at various points. The controlled impedance helps ensure the efficient propagation of signals, without disturbance and distortion. The impedance (Zo) of a circuit is an AC characteristic and is measured in Ohms (Ω). Target value of impedance is 25 Ω - 125 Ω.
The impedance of a PCB trace is determined by factors, such as resistance, capacitive reactance, and conductance. What contributes to these factors? Well, the answer is, these factors are decided by elements such as physical dimensions of the trace, dielectric thickness, and the dielectric constant of the substrate material used in the PCB. The value of impedance is decided by the following factors:
Characteristic impedance is one of the most common types of controlled impedance. The following are a few more important types referred in the market:
Controlled impedance is considered ideal for high-frequency digital applications:
The following are some common mistakes to avoid while producing controlled impedance circuits:
All this means, you should consider purchasing these controlled impedance circuit boards from reliable and experience manufacturers only. Creative Hi-Tech is one of the popular manufacturers of controlled impedance circuit boards in the USA.