I believe that most engineers know surge protection design in signal ports, in order to improve the surge protection effect, often with TVS and resistance, used together, but TVS and resistance in the design layout, the effect will be very different, of course, the layout of the reliable method of these two kinds of layout: a: protection resistor placed in front of the TVS pipe layout two: protection resistor placed in the back - TVS tube as shown in figure 1. In order to determine the impact of two different layouts on the interface surge protection performance, test the interface of a product. The experimental setup is shown in Figure 2 below. The surge generator is set to 10 consecutive times (positive and negative for each of the 5) output 1.2/50uS standard surge voltage, surge voltage according to different ports to set different voltage. The test results are shown in Table 1 and table 2.
Table 1 the test data for the protection resistor placed in front of the TVS tube, table 2 for the protection resistor placed on the back of the TVS test data. From the test data shows that the ability of anti surge voltage interface table 1 than in Table 2 and table 1 to a lot worse, failure are caused by damage resistance and TVS pipe was not damaged; table 2 interface failure is due to TVS tube breakdown caused by the short circuit resistance, and no damage. It can be seen that the resistance placed in the back of the layout of the TVS pipe placed when the protection of the surge is stronger.
This article analyzes and summarizes:
We can learn from the above, the resistance can be connected in series with the TVS tube as a protection device to prevent the surge current to play a limiting role, but in the layout, resistance to placed in the back of the TVS tube, TVS tube because of the action, the impedance of TVS pipe is very low, most current flows from the TVS tube, and current flows in R is far less than the current flowing through the TVS tube, but the tube current can withstand the flow of TVS is much larger than the resistance, it is easier to gauge interface resistance 1 failure. At the same time, it is also necessary to consider the resistance power and package size when the resistance is used to prevent surge. In this regard, you still do not understand the contents of this article or related TVs do not understand the problem, you can contact the small phone: 86-755-88365418 email: evan@tergy.com.