1. Cost: The main profit of any company that sells hardware products is generally the sales price - COGS, and the COGS 90% depends on the design. The rest is the production cost. This price is generally transparent, and there are many OEMs. The competition is fierce. Although the design cost of 60% depends on the price of the main chip (this mainly depends on the results of negotiations between the company's senior management and the chip manufacturer, HW's role is limited, more is the system engineer to make decisions on what chip can meet product requirements and software functions. Demand), but the remaining resistors, capacitors, inductors, diodes, transistors, protection devices, interface devices, logic chips, logic functions, chiplets, power circuits are all HW owners, of course, there are reference designs, but generally refer to In order to better reflect the good performance of the chip, it is generally preferred to use more expensive, better performance devices, which should be combined with the company's device library. My experience is to look at the company's similar product design, look at what mainstream devices are used, after all, for components, the price has a lot to do with the purchase volume, the price caused by different purchases may vary several times. 2. Signal Integrity: Signal Integrity: The main impact of two aspects: SI and Timing Timing, bad SI design will have a strong overshoot/undershoot, spike Spike, which will cause the corresponding frequency N resonance frequency emission; bad SI design will lead to High / low Unstable, or rise/fall time Rising Time/Falling Time is too long, or the clock is unstable, which will cause misjudgment when sampling Sample at the receiving end. In fact, the receiving end will not make mistakes, only the signal is wrong. . In the schematic design, the SI design is mainly solved by impedance matching (serial resistance), supplemented by appropriate decoupling filter capacitors; mainly on the PCB, generally speaking, the more PCB layers, the better the SI Of course, here is a trade-off with Cost. 3. Power Supply Design: Although the larger companies have specialized power supply design engineers, the basic Power design capability is still very important for HW. In theory, any circuit is a power supply, and any circuit problem can be attributed to A power problem, only deep understanding of the power circuit, in order to understand and deepen the board, especially for analog circuit problems, can think of using analog circuits to design some simple circuits, rather than laborious to use logic circuits. 4. Safety Safety: For the interface circuit, the main cost is in the safety device, how much voltage and current strike is this interface? This is a good consideration of what device to use, fuse? PTC? TVS? high voltage capacitor? Mainly for the corresponding specifications of various countries (safety is also), for all kinds of signals that may generate radiation, fully consider decoupling, filtering, for the EU is generally EN55022/EN55024, for the United States is generally FCC Part 15, EU It is slightly different from the US radiation standards, and the EU standards are slightly stricter. Now advocates environmental protection, operators are also, HW must also consider power saving, such as using more efficient power circuits, replacing LDOs with PWM, and a more efficient conversion topology. Chip integration is getting higher and higher, the power consumption of a single chip is from a few watts to tens of watts now. Heat dissipation is a big problem, and with the increase of the interface speed, the power consumption of the interface chip is also increasing, resulting in the whole system being :heat! This requires a good consideration of the heat dissipation problem, from the layout of the PCB, to the use of the heat sink Heatsink, to the use of the fan, there are many considerations. 8. Noise: Fans are the best way to dissipate heat, but the problem is noise. The ITU also has clear specifications for the noise of communication equipment. This requires balancing the number of fans, speed, direction, and control. The device selected by HW must be purchased by Sourcing, and generally consider the problem of second source, and the problem of lead time. It cannot be said that a rare device produced by only one small company can be used. In case this device EoL, What do you do? Can only modify the design, this will be a big loss! What is the value of the MTBF of the entire system? What is the most risky device? What is the percentage of working Margin per device? Mainly for the consideration of the factory, it must take into account the production test of the factory and facilitate the production. If your test is complicated, it will greatly reduce the production capacity and yield of the production line, thus affecting the supply and production of finished products. For the reference design, the most useful places are the power supply circuit, decoupling filter circuit and Layout design. As for the bus connection, reset circuit, clock circuit, interface circuit, etc., it is generally required to design the case according to the company's device library. The industry's mainstream devices/programs are being modified. So don't be superstitious about the reference circuit. It's just a reference. It's too superstitious reference design. I haven't figured out the specific functions/parameters of the chip yet. I will come over to COPY. Even if I can work, there are definitely many problems in terms of cost. Anti Drop Phone Case,Best Anti Drop Phone Case,Iphone Case Anti Drop,Anti Drop Phone Case For Sale Guangzhou Jiaqi International Trade Co., Ltd , https://www.make-case.com
5. Electromagnetic compatibility EMC/EMI:
6. Power Consumption:
7. Thermal/Cooling: 
9. Component Sourcing:
10. Reliability:
11. DFT: design for test / DFM: design for manufacture: