CN101470765A - Length compensation method for differential mode line pair and its length computing method and storage medium - Google Patents

Abstract

The invention discloses a length compensation method of differential mode line pairs and a compensation length calculating method of a winding delay line. The compensation length calculating method comprises counting the beveled edge number A and the rotor angle number B of the winding delay line, measuring the line width W of the winding delay line, measuring the parallel line-segment height S1 of the winding delay line, and calculating the equation I, and obtaining the compensation length L diff of the winding delay line.

Description

The length compensation method that differential mode line is right and length calculation method and medium

Technical field

The invention relates to a kind of circuit layout, and particularly relevant for the right length compensation method of a kind of differential mode line and the compensating length computing method of winding type lag line thereof.

Background technology

Along with being showing improvement or progress day by day of science and technology, the frequency of operation of digital circuit is more and more higher, and therefore many unfavorable galvanomagnetic effects also produce.(Printed Circuit Board PCB) is example, when signal transmits on transmission line, owing to electromagnetic wave can outwards transmit by medium, and produces the electromagnetic radiation phenomenon with printed circuit board (PCB).This electromagnetic radiation meeting influences other electronic component operate as normal, and promptly so-called electromagnetic interference (EMI) (ElectromagneticInterference, EMI).In the digital circuit, the unit intensity of element continues to increase now, makes to face many tests on the line design of PCB.In practical wiring, can cause critical circuits not isometric because of factors such as corner to the path of (for example differential mode line to).

Fig. 1 is the right configuration figure of explanation configuration differential mode line.P11 and P12 represent the two-lines road that differential mode line is right respectively among Fig. 1.After differential mode line was to P11 and P12 process corner, clearly the signal path lengths of outer ring circuit P11 must be also longer than the signal path lengths of inner ring circuit P12.This path caused phase differential inequality (phase skew) can produce common mode noise (common mode noise), and then the source that the signal integrity degree is impacted and produces electromagnetic interference (EMI).Therefore, identical in order to ensure the critical circuits path, generally can use " line crawls " line design skill (serpentine) and compensate the path of inner ring circuit P12.

The line that crawls that conventional art is designed is all estimated line route length with the center line (shown in the dotted line among Fig. 1) of circuit.This practice seems rationally, yet actual current but not necessarily can follow the center line of circuit to flow.This common technique will cause configuration can't reach the isometric requirement of actual signal path, and then form the common mode noise that can't ignore.

Summary of the invention

The invention provides a kind of compensating length computing method of winding type lag line, to calculate the compensating length of actual signal path in the winding type lag line more accurately.

The invention provides the right length compensation method of a kind of differential mode line, right to design the isometric differential mode line of actual signal path more accurately.

The present invention proposes a kind of compensating length computing method of winding type lag line.These compensating length computing method comprise: the hypotenuse of counting winding type lag line is counted A; The corner of counting winding type lag line is counted B; Measure the live width W of winding type lag line; Measure the parallel segment height S of winding type lag line ₁And calculation equation $L_{\mathrm{diff}}=A(\sqrt{2}-1)(S_1-(5W/6))+B\{\sqrt{{\left[\frac{W}{5}(1+\sqrt{2})\right]}^2+{\left[\frac{W}{5}\right]}^2}-\left[\frac{W}{5}(1+\sqrt{2})\right]\},$ To ask for the compensating length L of winding type lag line _Diff

The present invention proposes the right length compensation method of a kind of differential mode line.This length compensation method comprises: the hypotenuse of setting the winding type lag line is counted A; Set the corner of winding type lag line and count B; Set the live width W of winding type lag line; Calculation equation $A(\sqrt{2}-1)(S_1-(5W/6))+B\{\sqrt{{\left[\frac{W}{5}(1+\sqrt{2})\right]}^2+{\left[\frac{W}{5}\right]}^2}-\left[\frac{W}{5}(1+\sqrt{2})\right]\}=0$ To ask for the parallel segment height S of winding type lag line ₁Set the parallel segment height S of winding type lag line ₁And near the right corner of differential mode line, the winding type lag line is assigned in the right inside cord of differential mode line.

The present invention provides a kind of computer-readable storage medium in addition, in order to the storage computer program.This computer program is in order to be loaded in the computer system and to make this computer system carry out said method.

The present invention is analyzed the actual current trend because of the physical geometry of utilizing the winding type lag line, and then derive more accurate length compensation method and compensating length computing method thereof, therefore can calculate the compensating length of actual signal path in the winding type lag line more accurately, and then it is right to design the isometric differential mode line of actual signal path more accurately.

For above-mentioned feature and advantage of the present invention can be become apparent, preferred embodiment cited below particularly, and conjunction with figs. are described in detail below.

Description of drawings

Fig. 1 is the right configuration figure of explanation configuration differential mode line.

Fig. 2 illustrates the layout that a kind of differential mode line is right according to the embodiment of the invention.

Fig. 3 A is the layout according to embodiment of the invention explanation checking circuit.

Fig. 3 B is the xsect of key diagram 3A.

Fig. 3 C is the layout of 45 degree differential mode corners among the key diagram 3A.

Fig. 4 is according to embodiment of the invention explanation differential mode line centering, not compensating length and the common mode noise analog result that adds the winding type lag line.

Fig. 5 illustrates the length compensation method flow diagram that a kind of differential mode line is right according to the embodiment of the invention.

Fig. 6 is according to embodiment of the invention explanation differential mode line centering, not compensating length and the common mode noise analog result that adds the winding type lag line.

Fig. 7 is according to embodiment of the invention explanation differential mode line centering, and the frequency domain differential mode of compensating length and adding winding type lag line does not change the analog result of common-mode response.

Fig. 8 is the compensating length computing method that a kind of winding type lag line is described according to the embodiment of the invention.

Embodiment

Below will propose embodiment, and come to be illustrated, in the hope of tool common knowledge in this area being looked for more can understand the present invention and can implementing according to this at the present invention.Certainly, the form that following embodiment can also computer program realizes it, and utilizes computer-readable storage medium to store this computer program, carries out following method in order to computer.

Following examples will (serpentine) realize the winding type lag line with " line crawls ".Present embodiment is analyzed the actual current trend and is derived more accurate formula, therefore can calculate the compensating length of actual signal path in the winding type lag line more accurately, and then it is right to design the isometric differential mode line of actual signal path more accurately.

Fig. 2 illustrates the layout that a kind of differential mode line is right according to the embodiment of the invention, wherein differential mode line right wherein dispose the winding type lag line in a circuit.In the process that the differential mode signal transmits in the line, run into corner, can produce the reflection noise of differential mode because of the uncontinuity of corner structure at drive end.And because the unequal cause of line length each other, it is poor if having time to cause between two signals, therefore just produces the common mode noise at receiving end.For the differential mode volume reflection severe exacerbation that integral body is caused, so present embodiment will be set parallel segment height S in the winding type lag line ₁The rough right interval S of differential mode line that equals.In addition, L among Fig. 2 ₁Expression parallel segment length, and W represents the right live width of differential mode line (also being the live width of winding type lag line).

With this understanding, present embodiment will compensate each differential mode corner with the winding type lag line of two broken numbers.Fig. 3 A is the layout according to embodiment of the invention explanation checking circuit.Fig. 3 B is the xsect of key diagram 3A.Right interval S=the 9mil of differential mode line in this hypothesis Fig. 3 B, the distance H 1=4mil of metal level below live width W=4mil, line thicknesses T=1.2mil, differential mode line adjust the distance, the adjust the distance distance H 2=13.2mil of upper metal layer of differential mode line, the dielectric coefficient ε of printed circuit board (PCB) _r=3.7.Layout to the checking circuit of Fig. 3 A is carried out time-domain analysis, to observe the situation that receiving end suppresses the common mode noise.In Fig. 3 A, drive end transmits a positive voltage signal with a circuit P42 wherein, and transmits a negative voltage signal with another circuit P41.The aforesaid voltage amplitude is about 1 volt, and signal elevating time is 50ps, the parallel lines segment length L of each winding type lag line ₁Be 3W (three times of live widths).

Fig. 3 C is the layout of 45 degree differential mode corners among the key diagram 3A.Fig. 3 C is carried out geometric analysis, can know that the length difference of 45 degree differential mode corners of this checking circuit is

2 Δ L=2 (W+S) tan (θ/2)=10.7696mil formulas (1)

, wherein θ is 45 degree.By following formula as can be known, behind the length difference of knowing 45 degree differential mode corners, under the condition of length coupling (with its length of middle line computation), the parallel segment height S of its two broken numbers winding type lag line ₁For

$10.7696=4(\sqrt{2}-1){\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="A200710307303E00111.png,A200710307303E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_1$ Formula (2)

, so S ₁=6.5mil.

Fig. 4 is according to embodiment of the invention explanation differential mode line centering, not compensating length and the common mode noise analog result that adds the winding type lag line.The right checking circuit of differential mode line shown in Fig. 3 A and Fig. 3 B has two differential mode corners.If not to this differential mode line to compensating its length difference (be the configuration of similar Fig. 3 A but do not dispose the winding type lag line), then its analog result shows to have sizable common mode noise (as the block curve of Fig. 4).And if this differential mode line is compensated its length difference to configuration winding type lag line (as the configuration of Fig. 3 A), then its analog result demonstration significantly reduces common mode noise (as the dashed curve of Fig. 4).Note that it is that center line with the winding type lag line calculates its compensating length herein, can calculate according to the setting of above-mentioned verification condition, when calculating its compensating length with center line, the parallel segment height S of winding type lag line wherein ₁Be required to be 6.5mil.By the dashed curve of Fig. 4 as can be seen, the parallel segment height S of winding type lag line ₁If 6.5mil, though significantly reduced the common mode noise, still have very important common mode noise amount.

In other words, from the analog result of Fig. 4 as can be seen, generally calculate the mode of the compensating length of winding type lag line, can't make common mode noise amount drop to minimum (common mode noise amount also has some compositions not suppress complete as can be seen from Figure 4) unexpectedly after its compensation with center line.Therefore, utilize the mode of getting center line to calculate the required compensating length of winding type lag line, its length from the required compensation of reality also has a paragraph poor.

Therefore, present embodiment is analyzed the actual current trend and is derived approximate correction formula, therefore can calculate the compensating length of actual signal path in the winding type lag line more accurately, and then it is right to design the isometric differential mode line of actual signal path more accurately.

Fig. 5 illustrates the length compensation method flow diagram that a kind of differential mode line is right according to the embodiment of the invention.Please refer to Fig. 5, at first the hypotenuse of setting the winding type lag line by the user is counted A (step S510), corner is counted B (step S520) and live width W (step S530).Above-mentioned steps S510～S530 can also by the default value automatic setting of application program it.

In step S540, calculate differential mode line for the formed line of certain corner (or some corner) to length difference L _DiffIn present embodiment, step S540 can application of aforementioned formula (1) calculate the acquisition line to length difference L _Diff, that is calculate L _Diff=2 (W+S) tan (θ/2).For example, if continue to use aforementioned authentication condition (W=4mil, S=9mil, θ=45 degree), then one 45 degree corner can make differential mode line to forming line to length difference L _Diff=10.7696mil.Next carry out step S550, with calculation equation

$L_{\mathrm{diff}}=A(\sqrt{2}-1)(S_1-(5W/6))+B\{\sqrt{{\left[\frac{W}{5}(1+\sqrt{2})\right]}^2+{\left[\frac{W}{5}\right]}^2}-\left[\frac{W}{5}(1+\sqrt{2})\right]\},$ Formula (3)

, to ask for the parallel segment height S of winding type lag line ₁By aforementioned formula (1) and Fig. 3 C as can be known, differential mode line is to causing its length difference L through 45 degree corners _DiffUnder the condition of length coupling, and consider that electric current can and flow according to " shortest path ", so suppose that the parameter that step S510～S530 of Fig. 5 sets is A=4, B=8, W=4mil, then the result of calculation of step S550 is S ₁=9.1mil.According to the result of calculation of step S550, set the parallel segment height S of winding type lag line then ₁(step S560).Carry out step S570 at last, each parameter setting according to above-mentioned near the right corner of differential mode line, is assigned to the winding type lag line in the right inside cord P42 of differential mode line (as shown in Figure 3A).

In order to verify that whether present embodiment can improve original mode with middle line computation compensating length, is applied to aforementioned formula (2) and formula (3) on the checking circuit shown in Fig. 3 A and the 3B separately at this.That is, the parallel segment height S that is obtained with middle line computation compensating length ₁=6.5mil, and present embodiment calculates the parallel segment height S that compensating length obtained ₁=9.1mil verifies the two formed winding type lag line respectively, to compare the difference that the two common mode noise suppresses.

Fig. 6 is according to embodiment of the invention explanation differential mode line centering, not compensating length and the common mode noise analog result that adds the winding type lag line.Simulate with the right checking circuit of differential mode line shown in above-mentioned Fig. 3 A and Fig. 3 B at this.If not to this differential mode line to compensating its length difference (be the configuration of similar Fig. 3 A but do not dispose the winding type lag line), then its analog result shows to have sizable common mode noise (as the block curve of Fig. 6).And if this differential mode line is compensated its length difference to configuration winding type lag line (as the configuration of Fig. 3 A), then its analog result demonstration significantly reduces common mode noise (as dashed curve and the dot-dash curve of Fig. 6).Note that dashed curve among Fig. 6 is that center line with the winding type lag line calculates its parallel segment height S ₁=6.5mil, the common mode noise analog result that is obtained; Dot-dash curve then is to calculate its parallel segment height S in the illustrated mode of present embodiment and Fig. 5 ₁=9.1mil, the common mode noise analog result that is obtained.By the dashed curve of Fig. 6 as can be seen, the parallel segment height S of winding type lag line ₁If 6.5mil, though significantly reduced the common mode noise, it still has very important common mode noise amount.Review the dot-dash curve of Fig. 6, the parallel segment height S of winding type lag line ₁If 9.1mil, its common mode noise amount is reduced to minimum, can realize the purpose of what is called " circuit is isometric " more accurately.

Fig. 7 is according to embodiment of the invention explanation differential mode line centering, and the frequency domain differential mode of compensating length and adding winding type lag line does not change the analog result of common-mode response.From analog result as can be seen, generally calculate the mode of the compensating length of winding type lag line, can't make common mode noise amount drop to minimum (common mode noise amount also has some compositions not suppress complete) after its compensation with center line.The illustrated mode of present embodiment and Fig. 5 is calculated its parallel segment height S ₁, it is the performance on time domain or the frequency domain no matter, can realize the purpose of what is called " circuit is isometric " more accurately.

Fig. 8 is the compensating length computing method that a kind of winding type lag line is described according to the embodiment of the invention.The needed compensating length of winding type lag line generally needs corresponding to the right length difference L of differential mode line _DiffThis length difference L _DiffCaused by 45 degree corners or other reasons.At this compensating length is treated as length difference L _DiffAt first count the hypotenuse of winding type lag line and count A (step S810), count B (step S820), and measure the live width W (step S830) and parallel segment height S of winding type lag line with corner ₁(step S840).Carry out step S850 then, to calculate above-mentioned equation (3), to ask for the compensating length L of this winding type lag line _DiffFor example, as shown in Figure 2, the hypotenuse of winding type lag line is counted A=4, corner is counted B=8; If live width W=4mil and parallel segment height S ₁=9.1mil, then the compensating length L of winding type lag line _DiffBe about 10.7696mil.

In sum, in the above-described embodiments because of analyzing the actual current trend, and then derive more accurate length compensation method and compensating length computing method thereof, therefore can calculate the compensating length of actual signal path in the winding type lag line more accurately, and then it is right to design the isometric differential mode line of actual signal path more accurately.

Though the present invention discloses as above with preferred embodiment; right its is not in order to limit the present invention; have in the technical field under any and know the knowledgeable usually; without departing from the spirit and scope of the present invention; when can doing a little change and retouching, so protection scope of the present invention is when with being as the criterion that claim was defined.

Claims (6)

1. the compensating length computing method of a winding type lag line comprise:

Count the hypotenuse of this winding type lag line and count A;

Count the corner of this winding type lag line and count B;

Measure the live width W of this winding type lag line;

Measure the parallel segment height S of this winding type lag line ₁And

Calculation equation $L_{\mathrm{diff}}=A(\sqrt{2}-1)(S_1-(5W/6))+B\{\sqrt{{\left[\frac{W}{5}(1+\sqrt{2})\right]}^2+{\left[\frac{W}{5}\right]}^2}-[\frac{W}{5}(l+\sqrt{2})\left]\right\},$ To ask for the compensating length L of this winding type lag line _Diff

2. the compensating length computing method of winding type lag line as claimed in claim 1 is characterized in that, this winding type lag line comprises the line that crawls.

3. computer-readable storage medium, in order to store a computer program, this computer program is in order to be loaded in the computer system and to make this computer system carry out the compensating length computing method of winding type lag line according to claim 1.

4. length compensation method that differential mode line is right comprises:

Set the hypotenuse of a winding type lag line and count A;

Set the corner of this winding type lag line and count B;

Set the live width W of this winding type lag line;

Calculate this differential mode line for the formed line of a corner to length difference L _Diff

Calculation equation $L_{\mathrm{diff}}=A(\sqrt{2}-1)(S_1-(5W/6))+B\{\sqrt{{\left[\frac{W}{5}(1+\sqrt{2})\right]}^2+{\left[\frac{W}{5}\right]}^2}-[\frac{W}{5}(l+\sqrt{2})\left]\right\},$ To ask for the parallel segment height S of this winding type lag line ₁

Set the parallel segment height S of this winding type lag line ₁And

Near this corner, this winding type lag line is assigned in the right inside cord of this differential mode line.

5. the length compensation method that differential mode line as claimed in claim 4 is right is characterized in that, this winding type lag line comprises the line that crawls.

6. computer-readable storage medium, in order to storing a computer program, this computer program is in order to be loaded in the computer system and to make this computer system carry out as the right length compensation method of differential mode line as described in the claim 4.

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