1. How to choose EDA tools?
Thermal analysis is not recommended as it is not strength for current PCB design software. The beginners of PLD design can use integrated environment provided by PLD chip manufacturers, and single-point tool is considerable when the design amounts can be more than one million.
2. Please recommend suitable EDA software for high-speed signal processing and transmission.
For conventional circuit design, INNOVEDA the PADS with simulation software are very good, and this design often occupy 70% of the applications. In the design of high-speed circuit, Cadence should be a cost efficient solution for analog and digital hybrid circuits. Of course, Mentor's performance is still very good, whose design process management is most outstanding.
3. Interpretation of the layers of PCB board:
Topoverlay ---- Top device name, also known as top silkscreen or top component legend, such as R1 C5, IC10.
Bottomoverlay ---- similarly, multilayer ----- If you design a 4-layer board and put a free pad or via, define it as multilayer then its pad will automatically appear in the four layers. If you only define it is the top layer, then its pad will only appear on the top layer.
4. For high-frequency PCB design with more than 2G, what should be noticed for routing and typesetting?
The high-frequency PCB above 2G is a radio frequency circuit design, which is beyond the discussion of high-speed digital circuit design. The layout and routing of the RF circuit should be taken into account with the schematic, since the layout and routing will cause a distributed effect. Moreover, the RF circuit designs some passive components through the parameter definition and special shape copper foil, so EDA tools should provide parametric devices and edit special shape copper foil. Mentor's boardstation has a dedicated RF design module that meets these requirements. Moreover, the general RF design requires special RF circuit analysis tools, and the eesoft of agilent is the most famous which have a good interface with Mentor tools.
5. For the high-frequency PCB design above 2G, what rules should be followed for micro-strip design?
RF micro-strip design should use three-dimensional field analysis tool to extract the transmission line parameters. All rules should be specified in extraction tools.
6. For all-digital signal PCB, the board has a clock source of 80MHz. In addition to screen (grounding), in order to ensure adequate drive capacity, what kind of circuit should be used to protect?
To ensure the clock drive capability, clock-driven chip is frequently used rather than being achieved by protection. Generally, the worry about the clock drive capability is caused by multiple clock loads. Using a clock driver chip, a clock signal can be turned into a few by point to point connection. When selecting the driver chip, in addition to guarantee the basic match with the load and the signal requirements (generally, the clock is the effective signal), the driver chip delay of clock should be counted in calculating system timing.
7. For a separate clock signal board, what kind of interface is generally used to ensure the small impact of the clock signal transmission?
The shorter the clock signal, the smaller the transmission line effect. Using a separate clock signal board increases the signal wiring length. And the grounding and power supply for single-board are also the problems. If you want long-distance transmission, it is recommended to use differential signal. LVDS signal can meet the drive capability requirements, but is not necessary if your clock is not too fast.
8. 27M, SDRAM clock line (80M-90M), the second and third harmonic of clock lines are just in the VHF band with great interference from the receiver. In addition to shorten the line length, are there any good ways?
If the third harmonic is large, while the second harmonic is small, it is probably because the signal duty cycle is 50%. In this case, the signal has not even harmonic. At this time you need to modify the signal duty cycle. In addition, for a one-way clock signal, the source-side series matching is generally used. This can suppress the secondary reflection, but does not affect the clock edge rate.
9. What is the topology of routing?
Topology, also called routing order, especially for multi-port connection network.
10. How to adjust the routing topology to improve the integrity of the signal?
This network signal direction is complex. Because topology is not the same for one-way, two-way signal and signal in different types of electrical level, it is difficult to say which topology is good for signal quality. As for the former simulation, selecting topology is dependent on the engineers who require to understand the circuit principle, signal type, and even wiring difficulties.
Statement: This post is only the personal view of the author and does not represent the opinions of ALLPCB.com.