Reverse Engineering PCB Board Analog Circuitry requires attention. In addition, there are still design elements that cannot be described on the layout drawing and schematic diagram. The circuit characteristics are changed in the form of wires, floating capacity, etc. In order to ensure the reliability of the PCB Board, these designs must be The elements are fully integrated into circuit design, package design and board design.
Reverse Engineering PCB Board Analog Circuitry
(1).round is not zero ohm
Although the ground impedance of a general circuit diagram is marked with zero ohms, in fact, the circuit pattern is unlikely to have no impedance (Fig. 3), that is, when a current flows into the circuit pattern, a voltage drop phenomenon is inevitable. Pressure drop is the root cause of various problems.
For example, when the transmitting end and the receiving end of the double-sided circuit board are connected by two points, the impedance between the grounding and the high current or the transition current generated by the switching will cause a potential difference between the two points, if the voltage becomes a noise voltage. If the signal overlaps, it will cause errors or even damage the components. Therefore, it is necessary to take effective measures against the SN ratio.
In order to prevent the potential difference between the groundings as described in item (1), the single-point grounding design is a common method used in digital analog hybrid circuits, but the frequency that this Reverse Engineering PCB Board Analog Circuitry can handle has a certain limit, even if it is thick. Short wire pattern, but when the frequency exceeds several MHz, it is possible to enter the range where the problem occurs.
Therefore, how to control the relationship between the current of the grounding wire and the voltage drop caused by the impedance is a very important issue in design. Fig. 5 is an example of a typical circuit pattern countermeasure. Although the counter-measure has a sufficient concept of common impedance, there are still many difficulties. Since the better ground can greatly reduce the cumbersome design, the recent high-frequency circuits almost all use multi-layer boards.
