I used the Altium`s impedance profile calculator and got the parameters, but then I double checked with a Saturn PCB tool - the results were significantly different (Picture 2). Although widely applied to coaxial cables against EMI susceptibility problems, the Zt parameter can be easily extended to coaxial cables EMI emissions. Eurocircuits also calculates the correct Differential Impedance values using the correct formula and not a ‘Rule of Thumb’ method. 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. To use these to design for a target impedance, simply cycle through various geometric values for the trace width until the calculator returns the target. The trace width (0. Differential Pair Impedance Calculator. At the receiver, the signal is recovered by taking the difference between the signal levels on. PCB Impedance-Calculation: Help with the dimensioning of the impedances of your circuit board. In high-speed digital protocols, data is sent over single-ended traces in a PCB that is impedance controlled; each individual trace is designed to have a specific impedance. 2. Differential Microstrip Impedance From Zo. Enter your board parameters and get instant results. A pair of tracks of the same cross-section (i. There are a lot of online trace impedance calculators specifically designed for differential traces. Its utility stems from its ability to. When you are creating your schematic, you must use one of the following suffixes when naming your differential pair nets: +/- (e. Still, as you correctly analyzed it is much better to think of the individual lines in a differential pair as two length-matched single-ended lines, both with the half impedance. You can see. 2. Following equation or formula is used for Differential Microstrip Impedance Calculator. High-speed designs carry a requirement for controlled impedance, crosstalk control, and the need for interplane capacitance. Let's match the impedance of the same signal since differential pair routing is completed when the impedance is matched properly. Finally, all calculators provide theoretical impedance values as they cannot take in to account the variables. 4mils/35um of copper thickness. PCB Impedance and Capacitance Calculator: Asymmetric Differential Stripline. For double termination, we want the source to provide R S = 50 W on each side for 100-W differential output impedance, and we want the input of the FDA to present a 100-W dif-ferential load. Microstrip Impedance Calculator. 1 of the Microstrip Calculator using H2 in place of h, εr,eff can be computed as specified in Eq. 6), the impedance will be approximately 50 Ohms. Parallel Wire Impedance, Inductance, Capacitance and Propagation Delay Calculator Results. 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. Using the formula, you can calculate the Differential Impedance (Zd) as follows: Zd = 2 * 100 / sqrt (1 + (2 * 100 / 20)) Zd = 200 / sqrt (1 + 10) Zd = 200 / sqrt (11) Zd ≈ 60. Such a stripline is constructed with two traces referenced to the same reference planes above and below the traces with a dielectric material between them. That means each trace would be a 50-ohm trace, if there were no coupling between the traces. These calculators give us essential trace spacing and differential pair spacing if needed. Differential pair impedance depends on a lot of variables in reality,. I used the KiCAD PCB calculator, asked the PCB manufacturer about the tangent loss (0. Use several of them and compare. Unfortunately, TxLine doesn't do coplanar waveguide for differential traces. Also note that your best bet may actually be VERY SHORT (few mm) traces, a thinner board or a 4 layer board :-) Thanks for your suggestions. They will give very similar answers. Notes: 1) Calculation assumes traces are centered vertically. 1. KiCad has a built-in impedance calculator!The impedance calculator determines the signal properties and clearances (first image), use that clearance in the via shielding Distance setting. A differential pair consists of two well matched, source-coupled transistors as shown in Figure 6-1. These values are trace width, substrate heights, substrate dielectric, and trace thickness. The calculator shows 90 ohms can be achieved using. This is an approximate critical ratio. This calculator finds both odd and even transmission line impedance. Everywhere on this curve, the differential impedance of the pair is 100 Ohms. transmitted across a twisted pair cable by a differential line driver and sensed at the far end by a. Those pairs connect via a dedicated FFC cable. You can use the differential impedance Calculator to find the differential impedance. Single-ended signals are fairly straightforward. The characteristic impedance is given by: Eq. Not too tricky. 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. 05 that is free software and very. The CAN bus shall be split-terminated with 120Ohm, 60Ohm for each line. But, you usually want some decent coupling between the traces, so a good single-ended impedance target for each trace is between. 0. 6mm spacing with a trace width of 0. Speedstack Si – Insertion loss & impedance PCB stackup design including Si9000e. This is a calculator used for determining the characteristic impedance of a microstrip. So, to calculate the differential impedance of Figure 1, simply calculate the impedance of Figure 3, and double it. This is good for routing space, but not so good for power delivery if there is a need for interplane capacitance. 10, 11. By Perrine Juillion / April 8, 2020. I believe the 100-ohm differential equates to 50-ohm single ended because you can think of the two 100-ohm impedances as being in parallel resulting in an effective 50-ohm single-ended equivalence. In Altium Designer you can easily change the width of both of the differential pair tracks, but if you do so the gap of the diff pair changes depending on the change of the width. Differential Pair Impedance Calculator Calculates the differential pair impedance of a balanced line. Capacitance – the impedance calculator uses the Impedance value to calculate the capacitance per unit length. Going through Saturn PCB Calculator - which is free and useful software for engineers. Therefore i tried using this paper to calculate a characteristic impedance of 60Ohm for a coplanar strip attaching the CAN-Transceiver to a Twisted Pair cable, the CAN bus medium. 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. Sorted by: 1. 331 1 2 5. Copper. The example below shows how adjusting the stitching via placement could affect a differential via. AC coupling capacitors can be positioned anywhere throughout the differential pair’s length. 08mm - this is the border of manufacturability, I don't think it is practical to go there but for the calculation it is just fun - and I get some 31Ohms. Schelkunoff in 1934, is a very convenient parameter for the prediction and control of EMI coupling through cable shields. These differential amplifiers are optimized for DC signals and are typically characterized by high gain, high input impedance, and high common mode rejection ratio (CMRR). 75 mm track on a 0. It also explains the factors that affect the impedance, such as trace width, dielectric constant, and frequency. You will want to control impedance with smaller variations in gap. The grounded differential coplanar wave guide is the differential version of the grounded coplanar wave guide and is used in high-speed digital systems that require maximum noise immunity. Just enter the given values for trace thickness. Use 3. Comparator tab . You can use all the calculators you want if you don't know the exact board make up they're using; they should be able to help you. 6 mm board that I want to create a 90 Ohm profile on. Differential pairs with vias and right-angle bends are acceptable. Polar or rectangular grids only allow direct reading of S11. 03) it gives me almost 160 Ohm - and even if use 53mil conductor height or. The trace width (0. Can I / should I add extra components to the bus traces, to reach the. Broadband Impedance Matching with Transformer; Ferrite Toroidal Coil (Amidon) Helical Coil Calculator; Impedance Calculator : XL, XC; Iron Powder Toroidal Coil (Amidon)They has confirmed me, that the used formulas are very simple formulas. Characteristic. . 8 substrates of various thicknesses. How field solvers such as the Si8000/9000 calculate impedance. Typical impedance tolerances are 10% and 7%, and can go as low as 5% or 2% in the extreme cases. Instrumentation amplifiers are analog subsystems that amplify low-level signals in the presence of high common mode noise. beammy. Single-ended impedance of 50 Ohm. Incidentally, the trace thickness parameter does have a significant effect. I need to route 100ohm differential pair without GNd I can't find any PCB calculator for parallel routing on one layer. Dr J Alan Staniforth. If the width of the trace is two times the height of the dielectric (for FR4, Dk from 4 to 4. I use the software a lot to calculate impedance, maximum current for t. Stripline is another type of transmission line that can be easily built on a pcb. look at a differential source driving a twisted pair to the FDA. Instant online PCB quote, get PCBs for only $2. #PCB #KiCad #HowtoIn this video, we show you how to create a deferential pair in KiCad. The JLCPCB Impedance Calculator computes track width values and recommended stack-ups from user-input values of board layer, thickness, copper weight, target impedance, trace spacing (for edge-coupled pairs), and impedance trace to copper gap (coplanar waveguides). A printed circuit board (PCB) mechanically supports and electrically connects electronic components on a circuit board. 5oz inner copper, 8 mil trace spacing) and a target differential impedance of 100 ohms, JLC's calculator suggests a trace width of 8. Jan 31, 2016 #2 FvM Super Moderator. , USB. net Forum comes closest to the proper track width. Hello Community, iam currently designing a board that contains an 100MBit Ethernet connection. Differential Pairs can be defined as an Electrical CSet or a Physical CSet. . Note: valid for (w/h) from 0. The most commonly used twisted pair cable impedance is 100 ohms. Eurocircuits’ Impedance calculator uses real values as defined in the supplier’s data sheets. USB traces must be 90 Ohms differential. The S50 Impedance. Going to route the following signals: 100R differential pair (Zo = 50R) 90R differential pair (Zo = 45R) Planning to use the stack up JLC7628, with a 4 layer PCB, in total 1. This is a tool that has been designed to determine the characteristic impedance (Z 0) of a twisted-pair cable. For differential pairs, see the addition at the end of the tutorial. At some point the amplitude will stay constant. Disc Air Capacitor Calculator; Impedance Calculator : XL, XC; Inductors, Transformers. The differential via design shown in Figure 2 was built and tested. There are many demands placed on PCB stackup design. 1 Answer. In other words, if you are designing to hit a differential impedance target. 5 mil as the thickness of 3313 prepreg when the controlled impedance tracks are on top/bottom, use 5. To find the impedance of a capacitor (Zc) and an inductor (Zl) in an AC circuit, you use the following formulas: For the capacitor: Zc = 1 / (2πfC) For the inductor: Zl = 2πfL Where f is the frequency, C is the capacitance, and L is the inductance. The differential pair—sometimes called the long-tailed pair—is a widely used building block in electronic circuits, particularly in op amps. Inductance (L) = nH/ cm. 5 mil as the thickness of 3313 prepreg when the controlled impedance tracks are on top/bottom, use 5. and thats the first time iam doing ethernet things. The auto-router will add a trace to match the longest trace as shown in Figure 5. 1. 0 and 0. Staff member. If you control impedance, you place a tolerance in the fabrication notes. There have been trace routing tools available for a long time that help with differential pair routing. The receiver, which is on the motherboard, is a standard LVDS receiver, with 100Ω termination resistors. An example of this calculation using the Si8000m Quick Solver is shown below in figure 4. Integrated Transmission Line Impedance Calculators. s4p files with Delta-L 4. The Si8000m assumes negligible insertion loss in the transmission line; should you wish to model insertion loss the Si9000e adds. case of Figure 1, the mismatch occurs between the characteristic impedance of the twisted pair (typically 100Ω) and the 4 kΩinput resistance of the DS26LS32A. Impedance and Differential Pairs in KiCad. 8 substrates of various thicknesses. 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. 01) and dielectric constant (3. Download Saturn Pcb Design Toolkit. 50 - 55 ohms). Click here to see the user guide of our impedance calculator. Try it now for free. 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. The Differential microstrip impedance calculator is used to compute the differential (Zd) and single-ended impedance (Zo) of an edge-coupled microstrip line just by entering the width, separation and thickness of the trace along with the dielectric thickness and constant of the coupled line. I'm unsure if the reference plane would be the GND and the PWR layers. 004” line/0. Twisted pairs are used with balanced signals. Use an online differential microstrip impedance calculator. Differential pairs are commonly found in high-speed data communication systems, such as those used in computer interfaces (e. The total length of the signal path is about 1,330mils. Return loss is an important parameter that indicates how well the impedance matches with aFor differential vias, stitching vias can affect the impedance, but the impedance is much more sensitive to antipad sizes and layer arrangement/Dk value on each layer. It has been correlated many times. For microstrip traces, a solid ground plane is needed under the signal traces. But I am not able to match this impedance. . In terms of how these calculators work, the impedance of a transmission line in a PCB can be calculated in four ways: Use the R, L, C, G parameters from the Telegrapher’s equations to calculate the impedance of the transmission line. The required values are trace thickness, substrate heights, trace width, and subtrate dielectric in the calculator above and press the "calculate" button. CSI-2 interface data pairs require a 100 ohm differential impedance. In the image below, I am comparing differential vias with merged. 3mm of the microcontroller), therefore i rounded the width to 0. 0. A cross-hatch plane is shown in the image below. NOTE: The formulas used in the program are valid for 0. This calculator is designed to calculate the characteristic impedance of a microstrip - a flat conductor suspended over a ground plane with a dielectric between them (see diagram below). The JLCPCB Impedance Calculator computes track width values and recommended stack-ups from user-input values of board layer, thickness, copper weight, target impedance, trace spacing (for edge-coupled pairs), and impedance trace to copper gap (coplanar waveguides). Formula: Applicability: w ÷ t ≤ 0. 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. If the ratio is about 0. Modeling approximation can be used to understand the impedance of the edge couple differential stripline transmission line. Make sure to follow below for efficient RS485. However, it will definitely take longer compared to using a calculator. 2. Fig 1 Typical Pi termination for a coupled line pair. Please provide a rating, it takes seconds and helps us to keep this resource free for all to use. Note: The 6-Layer board temporarily only provides JLC3313 Stackup. Parallel Wire Impedance (Zo) = Ohms. User Interface. 2) S/T > 5. 36 mm substrate, has an impedance to ground, unbalanced, of about 49 ohms. Ask the board manufacturer for the values. A cheap unshielded laminated polyester FPC cable with 0. Calculates the differential pair impedance of a balanced line. When a differential pair is routed on a printed circuit board we assume that the signals will be of equal magnitude and opposite polarity. EEWeb offers a free online twisted pair impedance (transmission line) calculator. g. Just as important as determining an. If you don't have access to a differential impedance calculator, or you don't know how to calculate it, then just keep trace lengths less than 0. Actually the "odd impedance" is the correct impedance to look at for the USB requirement of 90 Ohms differential impedance. This calculator determines the impedance of a symmetric differential stripline pair. Edge-Coupled Microstrip. Microstrip construction consists of a differential pair and a single reference layer (typically ground). 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. When selecting trace geometry, priority should be given to matching the differential impedance over the single ended impedance. Now it has only one narrow track/via for GND connection. In differential pairs, each trace in the pair carries the same magnitude, but opposite polarity. Try it now for free. Skin Depth Calculator. Impedance in your traces becomes a critical parameter to consider during stackup. Differential pairs are defined on the schematic by placing a Differential Pair directive (Place » Directive) on each of the nets in the pair. But I'm unsure if the Height I entered is. This calculator is designed to calculate the characteristic impedance of an edge-coupled microstrip. 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. This calculator. 331 1 2 5. Description. The best differential coplanar waveguide calculator can account for all of these effects simultaneously and without a complex 3D field solver. Return loss Return loss is another way to look at impedance in the frequency domain. • If finite tail impedance and asymmetry are both. This ensures that the receiver. The other yellow rectangle is the USB connector. You will need to know the dielectric constant and the copper thickness to calculate trace impedance. The differential pairs should be loosely coupled. These values are trace width, substrate heights, substrate dielectric, and trace thickness. To calculate this, you need some values. Differential Protocol: Select the desired protocol from the dropdown list, this list will autofill the Target ZDiff edit box. Both gives me only 20 Ohm differential impedance. Use several of them and compare. 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. D_P and D_N) KiCad looks for these suffix pairs when using the differential pair routing tool during PCB layout. The Si8000m adds enhanced modelling to predict the finished impedance of multiple dielectric PCB builds and also takes into account the local variations in dielectric constant on close spaced differential structures. 25, but gives me nice trace from the module to the stub then to microcontroller. Agilent's LineCalc tool calculates Z odd = 50. Length of both tracks should be the same. Just as. Differential Pair Calculator The Differential Pair Calculator is used to perform what-if analysis to determine what values of Primary gap and width are needed to get specific differential and single line impedance. 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. Then enter the values of the impedances as complex. This release sees the introduction of the Simbeor® electromagnetic Signal Integrity engine. 11. model impedance by combining Polar's proven boundary element field-solving engine with easy graphing of process windows. width|space|width. Typical values for most common differential signal types are 90 ohms differential, 100 ohms differential or 120 ohms differential. It may have either one output or a pair of outputs where the signal of interest is the voltage difference between the two outputs. Even and Odd Mode Impedance 3. pair impedance with predifined traces’ gap. Keeping the final. For sample: 45-46 Ohm single end traces impedance can be used in diff. 0 for analysis with Si9000e. We recommend the software from Polar Instruments if you want to get exact impedance calculation. Tightly coupled pairs (within a pair) are quite common and this has the advantage of having a somewhat higher single ended impedance on a per track basis within a differential pair which is often easier to implement. Going through Saturn PCB Calculator - which is free and useful software for engineers. The PCB Impedance Calculator in Altium Designer. There’s an actual free 2D impedance calculator out there (arbitrary transmission line calculator, or ATLC). Twisted pairs are used with balanced signals. Often when working with wires it is easy to create large return path loops if one is not paying close attention. Use that. to NFThe impedance of the structure is the ratio of the voltage between, and the current in, the conductors. High-quality circuit boards as prototype and series at reasonable prices. It renders fairly accurate results suitable for use in circuit board manufacturing and engineering analysis. 8. Route differential pairs symmetrically and keep signals always parallel. When these traces are routed together in close proximityDifferential Pairs. It combines the power of an N-channel MOSFET with a P-channel MOSFET in a single package. g. A microstrip line is a type of electrical transmission line used to convey microwave-frequency signals and consists of a conducting strip separated from a ground plane by a dielectric layer known as the. Hello! I'm trying to calculate the trace width for a differential pair (carrying MIPI CSI-2 signals), using JLC's impedance calculator. This curve defines. A differential stripline pair refers to two traces located between two reference plane layers, which are routed as a differential pair. Grounded Differential Coplanar Wave Guide. Calculate Z diff, Z com, Z odd, Z even from transmission line parameters 2. microstrip Zo vs Edge Cpld Ext Zo). Although widely applied to coaxial cables against EMI susceptibility problems, the Zt parameter can be easily extended to coaxial cables EMI emissions. Differential Impedance Ω. Question #1: How to determine the required spacing between length-matched signals or differential pairs and the adjacent layers? If you are length matching that implies that the interface is probably fast enough to require controlled impedance. The topology pre-dates the solid-state era and is generally attributed to Alan Blumlein, when it appeared in one of his patents in 1936. This assumes ~0 trace thickness. The differential pair is all about balance. Z 0 now meets your requirements. 6 inches - this is very easy to do; If you can access a differential impedance calculator, then use. Details: In the list below, [1] is the reference design stackup information; [2] and. A twisted-pair cable is simply two wires that are twisted together so as to reduce radiated EMI (electromagneticinterference) and mitigate the effects of received EMI. 90 Ohm Differential Pair: 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). Also, it has got. 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. Is this a good practice for Ethernet? This is a capture of the PCB right now: This is the schematic that I am using. High speed PCBs and signaling standards almost entirely use differential pairs with precise impedance. FWIW, the calculator I've used in the past is called Polar SI8000 which apparently has been superceded by Speedstack PCB. 1-11. 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. The following are typical line widths and spacings for the more common impedance values when using ½ OZ copper: 50 Ohm Single Ended: 0. This is the same calculator integrated in other open-source tools like the microwave circuit simulator Qucs, or the circuit board design tool KiCad. The edge couple differential microstrip transmission line is a common technique for routing differential traces. 1<W/H<3. $egingroup$ @Bryce, whether the individual line's impedance is half the differential impedance depends on whether the pair is "strongly coupled" or "weakly coupled". To achieve impedance control, PCB design software with an integrated field solver can help in designing the right trace width for the HDI layer stack-up. For an embedded (internal) microstrip, the formulas provided in paragraph 4. Such a microstrip is constructed with two traces referenced to the same reference plane with a dielectric material between them. For a printed circuit board (PCB) this is a pair of traces, also known as a differential pair. Learn how to design. 5; w, t, s, h > 0;Changing the stack-up will affect the calculated trace width for impedance-controlled traces; however it will not automatically update existing traces. 62 Ohms. To examine impedance variations, select the Impedance Workflow option in the analysis toolbar. Backwards crosstalk creates a pulse width that is twice that of the propagation time of the pulse traveling the coupling distance. In other words, if you are designing to hit a differential impedance target (such as. High-speed differential pair signal traces need to be routed parallel to each other with a constant spacing between them. There is a slightly different, but tightly coupled question here with this impedance calculator: "stripline differential impedance": Stripline here seems to be placed in some inside layer. edu; Home; Members. Impedance Calculators. 15 mm spacing. The i. N and P-Channel Matched MOSFET Pair The ALD1105 by Advanced Linear Devices is engineered for precision and performance. RS485 uses differential signaling for the cable of 100Ω or 120Ω, the terminating resistance should match the cable. 300" away from the Ethernet front end. We often say that PCB traces should simply have 50 Ohm impedance, but this becomes more complicated when dealing with coupling between differential pairs. The IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a. Twisted pair: qquad footnotesize ext {Impedance} = frac {120 imes ln (2s/d)} {sqrt {varepsilon_r}} Impedance = εr120 × ln(2s/d) As you can see, it is not overly complicated to calculate by hand, but it will definitely take longer than using our calculator. For example, a single 0. PCB Trace Impedance Calculator; Electromagnetic Compatibility Laboratory. 29 mm width traces to obtain 100 Ohms ZDiff while using 0. The formula used in this calculator is an approximation for the characteristic impedance of a coplanar waveguide: scssCopy code. This 100 Ohm has no ground connection. USB traces must be 90 Ohms differential. This rule maintains the desired signal impedance. If it has more impedance for the peak current than the signal path has, it’s useless or at least less effective. The calculator is available in the Electrical Domain in Constraint Manager, from theTable 1-1. This definition effectively makes it equal. A PCB impedance calculator is necessary to set the constraints for trace structures during fabrication; they can vary in complexity, speed, and accuracy. Even mode impedance for commonly-driven transmission lines . 19mm) traces with 7. Note: The results are only for approximation and rough estimation, the final values and the. Differential impedance is defined as the impedance between the two lines when the line pair is driven differentially. 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. With this combination of powerful impedance modeling you can quickly determine the manufacturing variations for each of your designs and model resin-rich areas between differential traces to achieve the highest yields from yourThis is the odd-mode impedance of the differential pair. Differential pairs: even or common mode?PCB impedance calculator – Single ended / Differential pair. D_P and D_N) KiCad looks for these suffix pairs when using the differential pair routing tool during PCB layout. D_P and D_N) KiCad looks for these suffix pairs when using the differential pair routing tool during PCB layout. Use that. Preferably, the length of the clock trace should be somewhere in between. This will be specified in your controller's datasheet in the DDR4 interface specifications. I tried using different line width (10mils,15mils,20mils,25mils,30mils) of the differential pair but it doesn’t help me. 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. While the edge couple differential symmetric stripline transmission line is a common technique for routing differential traces. best to use a stackup calculator to provide quick ‘what if’ analysis of the possibilities. 6mm 4 layer PCB, 1oz outer copper, 0. Differential pairs: even or common mode? PCB impedance calculator – Single ended / Differential pair.