There is no strict distinction between high-frequency and high-speed circuits, just a general category of artificial design for different design problems. Here are some of the understandings I have compiled before.
"High-speed circuits" have become a term often mentioned by today's electronics engineers, but what exactly is a high-speed circuit?
This is indeed a concept of “familiarity” and “fuzziness”.
In fact, the industry does not have a unified definition of high-speed circuits. Generally, there are many opinions on the definition of high-speed circuits. Some people think that if the frequency of digital logic circuits reaches or exceeds 45MHZ-50MHZ, and works above this frequency, The circuit has already taken up a certain amount of the entire electronic system (say 1/3), which is called a high-speed circuit;
Some people think that there is no big connection between high-speed circuits and frequencies. Whether high-speed circuits depend only on their rise time; others think that high-speed circuits are the ones that we have not touched in the early years, or that can produce and take into account the skin effect. Circuits; more people define the high-speed quantization, that is, when the digital signal in the circuit has a delay of more than 1/2 rise time on the transmission line, it is called a high-speed circuit. The final definition is accepted by most designers.
In addition, there is a concept that is easy to be confused is the "high frequency circuit". What is the difference between "high frequency" and "high speed"?
For high frequencies, many people understand that the signal frequency is higher. Although this view cannot be said to be wrong, for high-speed electronic design engineers, the understanding should be more profound. We should consider the natural frequency of the signal. When the signal is transmitted with the accompanying effects of higher-order harmonics, we generally use the following formula to define the emission bandwidth of the signal, sometimes called the EMI emission bandwidth:
F = 1 / (Tr * π), F is the frequency (GHz); Tr (nanoseconds) refers to the rise or fall time of the signal.
Usually when F>100MHz, it can be called high frequency circuit. Therefore, in the digital circuit, whether it is a high-frequency circuit is not the level of the signal frequency, but mainly depends on the rising edge and the falling edge. According to this formula, we can estimate that when the rise time is less than 3.185 ns, we think it is a high frequency circuit.
In general, if you must give a distinction between "high-speed circuits" and "high-frequency circuits," high-speed circuits mainly look at the relationship between the rise/fall time of the signal and the delay of the transmission line. Of course, it may be greater than 1/2. The rise time may also be 1/4, 1/6 or 1/8 depending on the application. For the definition of high-frequency circuits, it is mainly based on the spectrum generated by the edges, which is the characteristic of the signal itself, regardless of the factors of the transmission line. Of course, the emission bandwidth is more than 100M, 500M, or 1GHz. This is not strictly defined, depending on the application.
发送反馈
历史记录
|
