Here you'll find insights into PCB design, tech trends, assembly issues, and trending topics
in the general news media as they relate to printed circuit board technology.
As experts in the manufacture and assembly of printed circuit boards, we work to make our blog a helpful resource on PCB topics and the industries that we work with, including automotive, consumer electronics, aerospace and many more.
In high-speed PCB digital circuit systems, impedance mismatch on the transmission line will cause signal reflection and signal distortion such as overshoot, undershoot and ringing, and when the delay TD of the transmission line is greater than 20% of the signal rise time RT, the reflection The impact can't be ignored, or it will bring signal integrity problems. The method of reducing the reflection is: matching the source impedance with the transmission line impedance according to the characteristic impedance of the transmission line at the driving end thereof, or matching the load impedance with the transmission line impedance at the receiving end, so that the source reflection coefficient or the load reflection coefficient is zero.
Design of the material composition of the board
The manufacture of high frequency printed circuit boards is very important for the choice of substrate materials. When choosing a substrate material, you should pay attention to the following four principles.
The current worldwide demand for environmental protection has made electronic products more demanding in the miniaturization of the Ministry of Energy. This has also spurred the advancement of high-speed and large-capacity electronic products for data and information processing. On the other hand, IT products that are personally demanded are also moving toward functional integration, high-performance (high-speed), and low-consumption power. In the signal transmission mode of electronic products, the parallel transmission mode develops toward a continuous mode. And the way in which optical transmissions have been added to electrical transmissions has begun to emerge. The high integration and high frequency development of electronic components has led to a continuous increase in the demand for high-frequency printed circuit boards.
(1) Cross circuit is not allowed in the printed circuit. For the lines that may cross, it can be solved by “drilling” or “winding”. That is, let a certain lead be "drilled" from the gap under other resistors, capacitors, and triodes, or "wrap" from one end of a lead that may cross. How to make the circuit complicated in special cases, to simplify the design It is allowed to bridge the wires to solve the cross circuit problem.
The high-speed PCB layout technology driven by electrical rules realizes the design strategy of signal crosstalk control.
Physical analysis and verification are playing a more and more critical role in ensuring the success of complex, high-speed PCB board and system level designs. This article describes how to suppress and improve signal crosstalk in signal integrity analysis.
In the design of electronic systems, in order to avoid detours and save time, the anti-interference requirements should be fully considered and avoided, and remedial measures against interference should be avoided after the design is completed. There are three basic elements that form interference:
To get the best performance from an electronic circuit, the board is the support for the circuit components and devices in the electronics. Even if the schematic design of the circuit is correct and the printed circuit board is not properly designed, it will adversely affect the reliability of the electronic product. When designing a printed circuit board, it is important to use the correct method, follow the general principles of PCB design, and conform to the requirements of the anti-jamming design and the layout of the wires. In order to design a PCB of good quality and low cost, the following general principles should be followed:
10 questions and answers.
Differential mode current and common mode current.
Generalization of PCB design principles (1-30)
In general, the most basic process of designing a board can be divided into three major steps.
Electromagnetic interference is caused by electromagnetic effects. As components and wiring on the PCB become more and more dense, electromagnetic interference will occur if improperly designed. In order to suppress electromagnetic interference, the following measures can be taken:
4 methods and solutions
The so-called source synchronization means that the clock strobe signal CLK is transmitted by the driver chip along with the transmission data, and it does not use an independent clock source like the common clock synchronization. In the source synchronous data transceiving, the data is first sent to the receiving end, and the strobe clock is sent to the receiving end for sampling and latching the batch of data after a short time. The schematic diagram is shown in Figure 2. The timing analysis of source synchronization is simpler than the synchronization of common clocks. The analysis methods are very similar. The analysis formula is directly given below:
In order to successfully latch data into the device, the data signal must remain active at the input of the receiving chip for a sufficient amount of time to ensure that the signal is correctly latched by the clock sample. This time is called hold time. In the common clock bus, the receiver buffer latches the data with the second clock edge while latching the next data to the data transmitter on the driver side. Therefore, in order to satisfy the receiving end holding time, it is necessary to ensure that the valid data is latched into the receiving terminal flip-flop before the next data signal arrives, which requires that the delay of receiving the clock CLKA is smaller than the delay of receiving the data signal.
One of the two necessary conditions for data transmission: the data at the input of RECEIVER generally has the required setup time Tsetup, which means that the data must be valid before the minimum time valid for the clock, and the time at which the data signal arrives at the input should be early enough. At the clock signal, the inequality satisfied by the settling time can be derived.
In the field of network communication, in ATM switches, core routers, Gigabit Ethernet, and various gateway devices, the system data rate and clock rate continue to increase, and the operating frequency of the corresponding processor is also higher; data, voice, and image transmission.