The flat flex cable used with Raspberry Pi CSI-2 camera interface has 0. 225m s = 2mm. The full S-parameter matrix for a differential pair is that considers common-mode and differential mode signals is an 8x8 matrix with the form shown below: Mixed-mode S-parameter matrix describing differential crosstalk and mode conversion between two differential pairs. Modeling approximation can be used to design the microstrip trace. Use via-s (absolutely not recommended for impedance-critical routes) hack the connector and remove some of its SMD pins, and wire one pair under those pins. Just as important as determining an appropriate trace width for a single-ended trace is determination of an appropriate spacing between two traces in a differential pair. 5 mil as the thickness of 3313 prepreg when the controlled impedance tracks are on top/bottom, use 5. This is more than the to times trace width which is recommended (also read as close as possibly). g. e. Altium Designer makes it easy to calculate geometry when you need to calculate impedance for differential pairs. 5mil clearance on a 63 mil board (1. 34, 40, and 48 Ohms single. These tools allow you to calculate a highly accurate impedance and propagation delay model for your differential pairs, and you can use these results to specify delay. In the time domain, we only care that the two ends of the differential pair cross the halfway transition between the HI and LOW states (assuming binary) at the same instant in time. g. When examining coupled transmission lines for common-mode or differential driving, you either have to source two separate TDR/TDT signals on the two lines simultaneously, or you have to measure the even/odd mode impedances. Z 0 Differential impedance (Ω): Calculate. Ready to give CircuitStudio a try? Click here to get started: impedance. The Impedance Calculator is a tool which allows a quick pre-layout estimation of several kinds of line impedances between different layers. . This makes the problem of determining impedance much more complex, and building an initial lossless model requires a larger set of formulas. Anyone have suggestion of one? Thanks Alan . Both LM and CM converge to zero as spacing goes to infinity. Typical impedance tolerances are 10% and 7%, and can go as low as 5% or 2% in the extreme cases. Gigabit Ethernet requires 100 Ω differential routing. Atlas Si for Touchstone – PCB Insertion loss processing with Delta-L 4. Fig 1. The standard specifies a two-wire differential bus; the characteristic line impedance is 120 Ohm. Finally, all calculators provide theoretical impedance values as they cannot take in to account the variables. To use this calculator, simply input your microstrip geometry and Dk value, and the tool will return the differential impedance value for a pair of microstrip traces. Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. If you viewed the via impedance calculator article linked above, then you likely noticed that stitching vias are needed when a specific via impedance needs to be targeted. . . The controlled impedance method applies to any trace that handles high-speed or high-frequency signals. manufactures will have a preferred tool that PCB designers can use to calculate the Impedance but there are also many available online. beammy. I am routing differential pairs in Altium 20 and using controlled impedance profiles. When you are creating your schematic, you must use one of the following suffixes when naming your differential pair nets: +/- (e. Anyone have suggestion of one? Thanks Alan . 4mils/35um of copper thickness. 3mm, as shown below: This increases the impedance slightly to 91. Differential Protocol: Select the desired protocol from the dropdown list, this list will autofill the Target ZDiff edit box. It is designed for precision signal. Use an online differential stripline impedance calculator. 3) to calculate trace width and. Testing and modelling characteristic impedance of differential pairs without ground. 9. The impedance calculators below are completely free to access and use. g. . and thats the first time iam doing ethernet things. Can I / should I add extra components to the bus traces, to reach the. Differential Impedance in Constraint Manager Advanced Constraints can be used to view the Differential Impedance in Constraint Manager. Both gives me only 20 Ohm differential impedance. $egingroup$ So basically your answer shows that the JLCPCB impedance calculator results are generally in the same ballpark as the proven field simulators. When enabled. The best differential coplanar waveguide calculator can account for all of these effects simultaneously and without a complex 3D field solver. Placing a Differential Pair directive on each pair net applies a parameter to the net,. When dealing with differential pairs, thi. thanks to 6 layers I am now pretty confident that I can place all diff pairs on top and bottom layers, directly above the ground planes. Note the differential pairs above that look like a strand of intestine have a constant gap between the pairs. 5 mil (0. The calculator is available in the Electrical Domain in Constraint Manager, from theTable 1-1. 100 Ohm Differential Pair: 0. e. Differential impedance: 90 ohms (tolerance: +/- 15%) On a typical 1. There are a lot of online trace impedance calculators specifically designed for differential traces. I tried using different line width (10mils,15mils,20mils,25mils,30mils) of the differential pair but it doesn’t help me. 75 m A = 9333 ohms. Just enter the given values for trace thickness. Sorted by: 1. USB 2 e. The resistance value chosen for the two resistors will be referred to as R D (for d rain resistance). Give it better GND connection if possible. Differential pairs should be tightly coupled throughout their entire length, so try to avoid variations due to pads, vias, or components along the routing path. Suggested Solution: for 100 Ohm Differential, use half the board thickness and make the tracks equal to the board thickness. Figure 1. Is this a good practice for Ethernet? This is a capture of the PCB right now: This is the schematic that I am using. This means the slope resistance is 7 V 0. $egingroup$ @Bryce, whether the individual line's impedance is half the differential impedance depends on whether the pair is "strongly coupled" or "weakly coupled". 1 is an example of making tradeoffs between routing layers and power plane capacitance for a ten-layer PCB. The following options in the Options for PCB Project dialog are used to configure this:. - Since you have 2 layer board, use a ground polygon beneath the RS485 communication (Both Control and Bus circuitry) - Several points in the layout as shown in the attached. Z 0 = 100 W is common for twisted-pair cables. The Si8000 Quick Solver is convenient to use for this purpose, as shown in Figure 4. Reaction score. There are single end trace impedance and distance between traces in the pair. That option operates on a single trace. The tool implements numerical solutions of Maxwell’s equations to render accurate and consistent results. The PCB Impedance Calculator in Altium Designer. PCB manufacturer normally provides information about PCB stackup and track geometry. This rule maintains the desired signal impedance. While the length and impedance are both important, 1mm of length differential will not affect your system's performance in any way, even for usb-2. This slope resistance, in parallel with the collector resistor (Rc) dictates what the output resistance of the amplifier is. Length matching is required per segment, and any length added (typically a ‘serpentine’ section) for the sake of matching a pair should be added near the location where the mismatch occurs. Choose a calculator to tune your PCB design. So, to calculate the differential impedance of Figure 1, simply calculate the impedance of Figure 3, and double it. 2. No, the single-ended impedance provided in differential line calculators does not matter. Figure 4. Dr J Alan Staniforth. If it has more impedance for the peak current than the signal path has, it’s useless or at least less effective. Twisted pairs are used with balanced signals. To be honest, I am no idea of the impedance on. 5mil (7628 prepreg) when tracks are inside. Transferring the Differential Pairs to the PCB Editor from Schematics. Voltage Divider Calculator 1 (Fixed) Voltage Divider Calculator 2 (Adjusteable) Capacitors. look at a differential source driving a twisted pair to the FDA. For an embedded (internal) microstrip, the formulas provided in paragraph 4. The 9-hole score differential allows golfers to maintain an up-to-date handicap index even when they only play a short. Track and gap widths are of concern in controlled impedance, but unless your speaker and mic connections (I assume audio frequencies) are going a long way you should not have any particular requirement for controlled impedance. Single-ended and differential pairs of strip lines. This ensures that the receiver. 25mm trace. , USB. Using this calculator, I found 100 Ohms by giving 9 mils of track width, 5 mils of track separation, 8 mils of dielectric (prepregs usually have a dielectric constant of 3. 6mm thick. Microstrip construction consists of a differential pair and a single reference layer (typically ground). 1<S/H<3. Differential Stripline Impedance Calculator. 2) S/T > 5. For microstrip traces, a solid ground plane is needed under the signal traces. Differential impedance is defined as the impedance between the two lines when the line pair is driven differentially. Formula: Applicability: w ÷ t ≤ 0. 1-11. By understanding the microstrip transmission line, designers can. 62 Ohms. $$Z_{0_{diff}} = 2Z_{0_{odd}}$$ Common Impedance. too. The same applies to common mode impedance, except that common mode impedance arises under common mode driving. The total length of the signal path is about 1,330mils. 3. The test sample consists of a pair of differential traces at the top layer, followed by a differential via to the inner traces, then a second differential via connects to the BGA landing pads at the top layer again. TransCalc is an open-source impedance calculator of various transmission lines based on common closed-form approximations. Differential impedance: This is the impedance of a pair of transmission lines. 29 mm width traces to obtain 100 Ohms ZDiff while using 0. This resistor is invisible to the even mode signals as the even mode content on each track is identical so no even mode current flows in this resistor. Even mode impedance is defined as impedance of a single transmission line when the two lines in a pair are driven with a common mode signal (the same amplitude and the same polarity). A common approach is to create a net class or differential pair class that includes these nets, then create a routing rule that targets this class, as shown in the images below. Speedstack Si – Insertion loss & impedance PCB stackup design including Si9000e. Check design with the online gerber viewer, Easy and quick PCB Price Calculator from JLCPCBTech Consultant Zach Peterson is talking Signal Integrity again today with a deep dive into Differential Impedance. This calculator determines the impedance of a symmetric differential stripline pair. Download the file here. If you control impedance, you place a tolerance in the fabrication notes. Differential pair routing. Most of the dedicated TL tools doesn't have this option, only if you use a full EM simulator. Select the same nets to analyze and run the simulation. Staff member. Note: The 6-Layer board temporarily only provides JLC3313 Stackup. edu; Home; Members. Ask the board manufacturer for the values. Si9000e – PCB insertion loss field solver. 05): Take account, the internal used formulas sometimes don't equal on Conductor Impedance tab and on Differential pairs tab (e. Converts short and long line . The concept of Shield Transfer Impedance (Zt), introduced by S. Differential: Ohms Overview This calculator is designed to calculate the characteristic impedance of an edge coupled stripline. 75 inches without impedance control; Keep the differential pair length mismatch within 0. Now select the two nets that you want to declare differential. Even mode impedance for commonly-driven transmission lines . There are four different types of impedance used in characterizing differential trace impedances. 3 Answers. 0. The board house achieves these tolerances by observing how their process affects impedance. The questions are mostly on the inner layer differential impedance item [4] below. The twisted pair helps create a more uniform inductance and capacitance per unit length of wire to ensure a constant impedance, by keeping the return path as close to the signal as possible. Distance between pairs should be (traces on top layer = microstrip) 4 times the layer. I have no luck finding an asymmetric differential stripline impedance calculator online. 5 mil (2116 prepreg) or 8. It incorporates many features that PCB designers and engineers are in regular need of like current capacity of a PCB trace, via current, differential pairs and much more. 2 High-Speed Signal Trace Lengths As with all high-speed signals, keep total trace length for signal pairs to a minimum. EEWeb offers a free online broadside coupled stripline impedance calculator. For double termination, the source needs to provide R O = 50 Ω on each side for a 100-Ω differential output imped-ance, and the line needs to be terminated with R L = 100 Ω. A mistake was made when designing a set of mother and daughter PCBs, resulting the daughter board to have its LVDS pairs at ~100Ω differential impedance, while the motherboard ~90Ω. The questions are mostly on the inner layer differential impedance item [4] below. Use an impedance calculator to determine the trace width (W) and spacing (S) required for the specific board stack-up being used. Thus, for optimal performance the resistors and MOSFETs must be matched. Finally, all calculators provide theoretical impedance values as they cannot take in to account the variables and. Agilent's LineCalc tool calculates Z odd = 50. First, consider a microstrip. We get a lot of questions about trace impedance and how to calculate the right trace size to hit a specific impedance in a manufacturable PCB. You can use the differential impedance Calculator to find the differential impedance. Modeling approximation can be used to understand the impedance of the edge couple differential stripline transmission line. Also, I tried the differential tools in KiCad, and I matched both pairs to the same length (otherwise, one track is about 6 mm longer). This calculator finds both odd and even transmission line impedance. Everywhere on this curve, the differential impedance of the pair is 100 Ohms. Components such as capacitors, resistors or active devices are generally soldered on the PCB. For a printed circuit board (PCB) this is a pair of traces, also known as a differential pair. To examine impedance variations, select the Impedance Workflow option in the analysis toolbar. 1. So, I am trying to figure out how to use Kicad’s PCB Calculator for “Coupled Microstrip Lines”: I’m unsure about what a couple of the parameters mean and can’t find an explanation in the docs (it just. Activity points. is the impedance between two differential pair signal traces. The i. I have no luck finding an asymmetric differential stripline impedance calculator online. Enter your board parameters and get instant results. The two traces of a pair should be symmetrically routed. Ideally the traces in the differential pair only interact with each other, as another answer said. ; Make sure D > 2S to minimize the crosstalk between the two differential pairs. 2. Edge-Coupled Microstrip. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. D_P and D_N) KiCad looks for these suffix pairs when using the differential pair routing tool during PCB layout. D+ and D-) _P/_N (e. . It is okay to specify the single-ended impedance for each differential pair member. For differential pairs, see the addition at the end of the tutorial. In some cases, we can also use 75-ohm differential impedance. 1 of the Microstrip Calculator using H2 in place of h, εr,eff can be computed as specified in Eq. 19mm) traces with 7. Differential pair PCB design basics, covering differential signalling benefits, references, impedance control, inter- and intra-pair matching, and terminatio. 5. The interactive routing and differential pair length matching features in Altium Designer® can be used alongside an integrated electromagnetic solver in the Layer Stack Manager. But, you usually want some decent coupling between the traces, so a good single-ended impedance target for each trace is between. In microstrip, this technique is ideal for routing differential pairs. Although widely applied to coaxial cables against EMI susceptibility problems, the Zt parameter can be easily extended to coaxial cables EMI emissions. Ask the board manufacturer for the values. Your signaling standards will determine your routing needs, including total maximum length, impedance standards, and the permitted length mismatch in differential pairs or parallel buses. ; Edge coupled differential pair ; Edge coupled internal symmetric differential pair ; Edge coupled internal asymmetric differential pair ; Edge coupled embedded differential pair ; Broadside coupled shielded differential pair. These values are trace width, substrate heights, substrate dielectric, and trace thickness. A cheap unshielded laminated polyester FPC cable with 0. The definition of the controlled impedance for this configuration does not require a ground. Learn how to configure, define, and use your design’s impedance requirements for single-sided and differential on each layer, with Altium Designer’s Layer St. One thing is for sure: When you are routing a high-speed PCB design you are going to be working with impedance-controlled routing and differential pairs. The reason for this is that the input impedance is what matters, and the input impedance at the via transition will look like the trace impedance (i. Impedance Calculator - Sierra Circuits. Enter your board parameters and get instant results. Our Impedance Calculator uses a 2D field solver to calculate near-end crosstalk based on the following equation: NEXT = V b /V a = ¼ (C mL / C L + L mL / L L). 0. We’ll go over how differential pairs can. To calculate the values, the designer needs to know the following information: Number of board layersDifferential Microstrip Impedance Formula or Equation. CSI-2 interface data pairs require a 100 ohm differential impedance. D_P and D_N) KiCad looks for these suffix pairs when using the differential pair routing tool during PCB layout. 3. Using the KiCad Impedance Calculator. Details: In the list below, [1] is the reference design stackup information; [2] and. Re: Calculating Differential Impedance for USB Differential Pair. Z 0 now meets your requirements. But in your differential pair, each line will have its own characteristic impedance, lower than 100 Ohms but higher than 50 Ohms (for instance a quick computing in Saturn PCB give me 77. We recommend the software from Polar Instruments if you want to get exact impedance calculation. Trophy points. Figure 3 shows the respective p and T models used to calculate the differential impedance (Z diff). LVDS PCB layout guidelines can be used for optimizing system performance by ensuring reliable signal integrity and reducing the chances of noise interference. While the edge couple differential symmetric stripline transmission line is a common technique for routing differential traces. Above 3-5 GHz• Differential pairs should be constructed as 100 ohm, controlled impedance pairs. Now it has only one narrow track/via for GND connection. mils: Distance between planes (B) mils: Relative Dielectric constant (Er) Differential Trace Impedance: ohms: References. • Keep the intra-pair and inter-pair skew between the device and RJ45 to less than 50 and 600 mils. These calculators will return an impedance value for pairs of trace width, substrate thickness, and copper weight values. This curve defines. 1. For differential pairs of microstrips, the formulas involved are much more complicated because coupling between the traces in the differential pair must be included in the impedance calculation. The resistance value chosen for the two resistors will be referred to as R D (for d rain resistance). Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. This value is often given the name “differential impedance. . Differential Pairs can be defined as an Electrical CSet or a Physical CSet. 2. I'm unsure if the reference plane would be the GND and the PWR layers. A differential amplifier multiplies the voltage difference between two inputs (Vin+ - Vin-) by some constant factor Ad, the differential gain. PCB Structures / Discrete Structures / Signal Management. We get a lot of questions about trace impedance and how to calculate the right trace size to hit a specific impedance in a manufacturable PCB. Z diff equals Ra||(2Rb) (p model) or 2R 1 (T model). The differential impedance target, as well as the single-ended impedance of each trace, is maintained by keeping the spacing between the two traces constant. The program used to calculate the impedances, assumes that, in manufacture, the. If you need to use differential pairs, you simply define traces in each layer as differential pairs and the impedance calculator will determine the correct spacing between traces. The surface finish is neglected. In the image below, I am comparing differential vias with merged. infinite mutual impedance. It is important to determine the characteristic impedance of a twisted-pair cable because this impedance should match the impedance. To set the rules for the classes we created above, we will follow these steps: Go to ‘Design’ >> ‘Rules. Follow the 8W spacing for differential clocks (or explore other rules) Even greater spacing is needed for high-speed differential signals. Details: In the list below, [1] is the reference design stackup information; [2] and [3] are the processes to get the result close enough to the reference design target so as to know the tool is valid; and [4] is the calculation in question because it is either 5. Use 3. look at a differential source driving a twisted pair to the FDA. LVDS PCB layout guidelines can be used for optimizing system performance by ensuring reliable signal integrity and reducing the chances of noise interference. Similarly, external fields can induce currents in a differential pair that are not equal in amplitude and opposite in phase. The even mode impedance is defined as the impedance measured by observing one line, while the other line is driven by an equivalent signal as the first. Against the two rows select the. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion. There’s an actual free 2D impedance calculator out there (arbitrary transmission line calculator, or ATLC). 5 – Calculation of Differential Impedance using online Calculator Notice that in the above case we get 100 Ohms for 18 mils separation between the + and – traces and 10 mils separation from the ground trace. So move to your left, use Omni's Cable impedance calculator and enjoy. Differential pair routing. The default units for all given values, except the subtrate. 1. Hence, without loss of generality, one. The HIGH level is brought up to a logic level (5 V, 3. Coplanar Waveguide With Ground Characteristic Impedance Calculator. A value of Z Line = 100 Ω is common for twisted-pair cables. These calculators ALL use wrong naming for "differential impedance". So move to your left, use Omni's Cable impedance calculator and enjoy. – Microstrip lines are either on the top or bottom layer of a PCB. Sorted by: 1. ; To. The types of traces where impedance control is applied are: Single-ended and differential pairs of microstrip lines. There is only one method I am aware of that gives any level of accuracy for differential via impedance calculations, and it starts from a calculation of the propagation delay through a pair of differential vias. to NFThe impedance of the structure is the ratio of the voltage between, and the current in, the conductors. The factors that influence differential pair via impedance will affect the input impedance seen at the vias. If R G = 402 W, we then need R T to be 114. (2. Since stripline traces are typicallyThis is why the differential impedance of a differential pair is often (but not always) slightly lower than two times the single-ended impedance of an individual trace. The differential pair impedance depends on the characteristic impedance and the spacing between each end of the differential pair. According to this guidelines, the differential pair (DP and DM signals of the USB) must have 90 ohm impedance to each other. As an example, If I want to meet the 80Ω diff/ 40Ω single impedances, taking the first inner signal layer, and using the Saturn Edge Coupled asymmetric calculator, the input would be: H2= 180um H1= 176um w = 0. Differential Pair Routing. 75 inches without impedance control; Keep the differential pair length mismatch within 0. 0 and CAN-FD might be slow enough to get away without it (and I'm honestly not sure, the performance will depend on the specific configuration), but if I were reviewing a layout with diff pairs without a ground reference I would be very unhappy with it. Use that. Take note that this assumes that the distance between the conductor and the planes is not the same for both reference planes; hence the asymmetric term. 25mm between the differential pair with a width of 0. While it is not necessary or a requirement to match the PCB 'stubs' it's probably a good idea if the speeds of your RS485 bus are high (+50MHz). pair impedance with predifined traces’ gap. Controlled impedance traces are determined by their physical dimensions and the property of the dielectric material used in the circuit board. This calculator computes the characteristic impedance of a twisted-pair cable based on its dimensions. The formula used in this calculator is an approximation for the characteristic impedance of a coplanar waveguide: scssCopy code. The two ends of a differential pair must be the same length. The vias on these differential pairs have their own impedance, which can create signal integrity problems on long interconnects. To achieve this, you may have to put small sections of trace tuning into the shorter line to equalize them. To use this tool, enter the values for. To achieve this, I used the built-in Calculator in KiCad. It is assumed that the output impedance of the. W is calculated to achieve a trace impedance (Z0) of ~50W and S is calculated to achieve a differential trace impedance of 90W. balanced), above a ground plane, have an impedance. Notes: 1) Calculation assumes traces are centered vertically. Several equations are. If the goal is to adjust the characteristic impedance, then you can likely do it by changing both width and spacing (keeping center-to-center the same) just as. This calculator requires symmetry in the trace widths and location between plane. The JLCPCB Impedance Calculator computes track width values and recommended stack-ups from user-input values of board thickness, copper weight, layer, target impedance, conductor spacing (for edge-coupled pairs), and conductor-to-ground gap (coplanar waveguides). As discussed in the first section of The MOSFET Differential Pair with Active Load, the magnitude of this amplifier’s gain is the MOSFET’s transconductance multiplied by the drain resistance: AV = gm ×RD A V = g m × R D. Preferably, the length of the clock trace should be somewhere in between. To calculate this, you need some values. Other calculators will use different equations for the same system, depending on the relevant approximations used in the derivation of the formula. INPUT DATA. KiCad has a built-in impedance calculator! Inductance – the impedance calculator uses the Impedance value to calculate the inductance per unit length. This kind of functionality is present in only some PCB design programs, and those with it have varying degrees of accuracy in their output. I used the KiCAD PCB calculator, asked the PCB manufacturer about the tangent loss (0. Differential Termination Techniques - • Textbook Reading Assignments 1. The differential impedance of MIPI tracks should be 100 Ohms, not 90 (USB requires 90). Common-mode impedance occurs with the pair driven in parallel from a. Click here to see the user guide of our impedance calculator. 6), the impedance will be approximately 50 Ohms. Dielectric Constant The. Email: info@multi-circuit-boards. User Interface. 0. 6 inches - this is very easy to do; If you can access a differential impedance calculator, then use differential. You will need to know the thickness of the dielectric you will be using as well as the relative permittivity (dielectric constant). For a printed circuit board (PCB) this is a pair of traces, also known as a differential pair. Altium Designer makes it easy to calculate geometry when you need to calculate impedance for differential pairs. 6 mm board that I want to create a 90 Ohm profile on. By Perrine Juillion / April 8, 2020. The calculator is available in the Electrical Domain in Constraint Manager, from theTable 1-1. > A good starting point is to ask you board house give you the widths and spacing for your stackup. We’ll go over how differential pairs can hel. Note: Units do not matter for this calculation as long as they are consistent. Modeling approximation can be used to understand the impedance of. The differential impedance will be a bit less than 2x the single-ended impedance. Two conductors can create a transmission line. Just as important as determining an. To make an effect transmission line with two wires it is best to create a twisted pair. Differential pairs: even or common mode?PCB impedance calculator – Single ended / Differential pair. This technique is used for routing internal layer differential pairs. The impedance of a differential via pair cannot be treated with a single via impedance calculator unless the vias are spaced far apart. AC coupling capacitors can be positioned anywhere throughout the differential pair’s length. I have task that I need to make adapter board which transforms gigabit ethernet connector RJ45 to another connector (not RJ45). Twisted Pair Impedance Calculator . Coupling can, however, be used to advantage in the form of differential impedance. The main takeaway for me: To get to around 80 ohms, I should not pull ground on the signal. The ratio of cross-hatch conductor width (HW) to cross-hatch pitch (HP) plays an. Differential pairs should be tightly coupled throughout their entire length, so try to avoid variations due to pads, vias, or components along the routing path. 5mm pitch. 3 V, etc. In other words, if you are designing to hit a differential impedance target. Follow the 8W spacing for differential clocks (or explore other rules) Even greater spacing is needed for high-speed differential signals. Saturn PCB - Toolkit for Impedance Calculation. In addition to the characteristic impedance of a transmission line, the tool also calculates: This calculator is designed to calculate the characteristic impedance of an edge coupled stripline. Select the Calculator button. This is the impedance between the two signal traces of a pair. Figure 6-1: Basic Differential Pair The most common application for a differential pair is the differential amplifier. The test sample consists of a pair of differential traces at the top layer, followed by a differential via to the inner traces, then a second differential via connects to the BGA landing pads at the top layer again.