How to restrain circuit is the design medium does the signal on circuit board string together faze?
[introduction] as circuit board go up line density is higher and higher, signal strings together faze always is hard the problem of oversight. Because can affect the regular job of circuit not just, still can increase the electromagnetism interference on circuit board.
a few high frequency signal on circuit board can string together faze to arrive MCU circuit or the I/O interface circuit of MCU, form in all modular voltage, well-known, in all when circuit is designed, modular voltage is most the thing that allows a person to be fed up with, accordingly, all sorts of likelihoods should avoid to cause circuit to work when designing circuit board abnormal in all string of faze of modular voltage.
Reduce the design principle that faze strings together on circuit board simple classify
1, make through equitable distribution individually yuan between parts of an apparatus even the line as far as possible short.
2, mix as a result of the degree that string together faze bring to bear on the frequency that disturbs signal becomes direct ratio, because this should make,high frequency line is far from sensitive line.
3, bring to bear on interference line and be disturbed line to want to be far from not only, had better want to be kept apart with ground wire, and avoid mutual parallel take a line.
4, be in multilayer in PCB board, bring to bear on interference line and be jammed line or sensitive signal walks along a line to want to use ground wire segregation or be apart layer.
5, be in multilayer in PCB board, bring to bear on interference line and be disturbed line to be in respectively the opposite two sides of ground wire or layer, namely secondary floor.
6, use the sensitive circuit with input inferior impedance as far as possible, can use bypass capacitance to reduce the input impedance of sensitive circuit when necessary.
What notice finally is, when wiring, the action that ground wire strings together faze to checking signal is very apparent, in interference the line is mixed get interference line direct cloth ground wire, can will string together faze to reduce 10db left and right sides.
Famous 3W wiring is regular
Restraining circuit board to walk along line signal to string together faze respect, have a very famous 3W wiring regulation (among them W is wiring width) , its content is: To width the line that is 3W, if other the distance between the center that takes a line and its center is more than 3W, can avoid string of trouble between signal. Following plan institute are shown.
Flux of 3W wiring regulation
According to this regulation, the of 75% flux that signal electric current produces was included inside 3W limits, the lead that wants photograph neighbour only is besides this limits, string of faze between signal very won’t serious, notable is, of the flux that signal electric current produces 98% include inside 10W limits.