ssd 512gb When DDR Termination Resistor puts the first particleadmin
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WeChat | Mr. Gao
=”fMn53xk7″> the current position of the termination resistor of DDR modules (one drive and many) in the industryssd 512gb, as if the differential line should be of equal lengthSSD 512GB, high-speed signals cannot go at right angles, and 25G signals cannot have long vias stubs, which is a kind of SI common sense category. So what do you think happens if you encounter a DDR module with misplaced termination resistors?
The placement of DDR module termination resistors with multiple drives is a common sense of SI, and we will place it at the last particle, just like the figure below.
DDR termination resistor is placed at the end, everyone will say, this kind of mistake should not be made, right? Unfortunately, we Mr. High-Speed have seen many, many cases, and there happens to be one case where even this rule is violated, and it is not in the design stage, it is a board that has already been produced….
This is a 1-to-4 DDR3 module, the customer’s goal is to run to 800M, but it turns out that it can only run to 400M, Mr. Gaoji also thought that it would be a difficult to locate the problem and optimize the design, and then took the customer’s board to see, and the result was such a mistake. Put the termination resistors in the position of the first grain, as shown in the topology of the clock signal in the figure below, and the red box is the termination resistor.
The first step we have to do is to verify the test results from the simulation, we simulate the clock and address signal of 800M respectively, and the results are indeed very consistent with the test situation.
the clock signal is completely failed at particle 2, and the address signal is also very small. In addition, the customer said that it can run 400M, and we also simulate the situation of 400M.
Well, 400M from the simulation point of view, whether it is a clock signal or an address signal has some margin, it is possible to test OK.
The problems and solutions of this board are very clear, after our company re-modified the board design, put the termination resistor back to its proper position, and there is no problem in testing 800M. This case is a lesson of “blood”, it tells us that some rules cannot be changed casually, especially the rules that have been recognized by the industry, otherwise the only thing that is designed and processed waiting for you is fail. The article in this issue is as simple as that, I hope it can inspire you to a certain extent.
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“e9CIIIG5”> through this case, Can you review what are the rules to follow in PCB design for DDR? hard disk wholesaleSSD OEMssd 512gb