Description

2. Interconnect: Adv. Layout. Transmission line misfortunes DC misfortunes in the conductorFrequency subordinate conveyor lossesFrequency subordinate dielectric lossesEffect of surface roughnessDifferential line lossesIncorporating recurrence space parameters into time area waveformsMeasuring LossesVariations in the dielectric consistent.

Transcripts

Interconnect I – class 21 Prerequisite perusing - Chapter 4

Outline Transmission line misfortunes DC misfortunes in the transmitter Frequency subordinate conveyor misfortunes Frequency subordinate dielectric misfortunes Effect of surface harshness Differential line misfortunes Incorporating recurrence area parameters into time space waveforms Measuring Losses Variations in the dielectric consistent Interconnect: Adv

Focus This part concentrates on inconspicuous fast transmission qualities that have been disregarded in many plans in the past These impacts turned out to be basic in present day plans Older BKM suppositions separate Become more basic as rates increment As velocities increment, new impacts that did not make a difference get to be distinctly noteworthy This expands the quantity of factors that must be appreciated Many of these new impacts are extremely hard to comprehend This section will layout a few of the most conspicuous non-perfect transmission lines issues basic to advanced outline Interconnect: Adv

Transmission Line Losses Key Topics: DC resistive misfortunes in the conduit Frequency subordinate resistive misfortunes in the channel Frequency subordinate dielectric resistive misfortunes Effect of surface unpleasantness Differential line resistive misfortunes Interconnect: Adv

Transmission Line Losses (cont\'d) These misfortunes can be isolated into two classifications Metal misfortunes Normal metals are not unendingly conductive Dielectric misfortunes Classic model are gotten from the arrangement of Electric dipoles in the dielectric with the connected field Dipoles will tend waver with the connected time fluctuating field – this takes vitality Why do we think about misfortunes? Misfortunes corrupt the flag sufficiency, bringing on serious issues for long transports Losses debase the flag edge rates, creating noteworthy planning push-outs Losses will at last turn into an essential speed limiter of our present innovation Interconnect: Adv

Incorporation Losses Into The Circuit Model An arrangement resistor, R, is incorporated to represent conveyor misfortunes in both the influence and ground plane A shunt resistor, G, is incorporated to represent Dielectric Losses R L G C Interconnect: Adv

DC Resistive Losses At low frequencies, the present streaming in a conduit will spread out however much as could reasonably be expected DC misfortunes are commanded by the cross sectional zone & the resistively (reverse of conductivity) of the flag transmitter Current moves through whole cross area of flag channel and ground plane w t Reference Plane The current in an average ground plane will spread out so much that the DC plane resistance is insignificant The DC misfortunes of FR4 are exceptionally irrelevant Interconnect: Adv

AC Resistive Losses As the recurrence of a flag expands, the present will have a tendency to move towards the outskirts or " skin " of the conduit - This is known as the " skin impact ". This will bring about the current to stream in a littler range than the DC case Since the present will stream in a littler zone, the resistance will increment over DC Coaxial Cable Cross Section at High Frequency Outer (Ground) conductor Inner (flag) conductor Areas of high current thickness Interconnect: Adv

Penetration into conductor Amplitude X Electromagnetic Wave The Skin Effect Why? At the point when a field encroaches upon a transmitter, the field will enter the channel and be constricted recall the flag goes between the conveyors The field sufficiency diminishes exponentially into the thickness of the conduit – skin profundity is characterized as the infiltration profundity at a given recurrence where the abundancy is weakened 63% (e - 1 ) of introductory esteem Interconnect: Adv

The Skin Effect – Spatial View The fields will instigate streams that stream in the metal Skin impact limits 63% (e - 1 ) of the current to 1 skin profundity – the present thickness will expire exponentially into the thickness of the conduit The aggregate territory of current stream can be approximated to be in one skin profundity in light of the fact that the aggregate range underneath the exponential bend can be compared to the zone of a square 1 0.9 0.8 0.7 0.6 0.5 Current 0.4 0.3 0.2 0.1 0 1 2 3 4 5 6 Interconnect: Adv Skin Depths

w t Microstrip Frequency Dependent Resistance Skin impact causes the current to stream in a littler zone Frequency subordinate misfortunes can be approximated by changing DC conditions to understand current stream Approximation expect that the current is restricted to on skin profundity, and it disregards the present return way The present will be packed in the lower bit of the transmitter because of neighborhood fields E-fields Interconnect: Adv

Microstrip Frequency Dependent Resistance Estimates The aggregate resistance bend will remain at around the DC esteem until the skin profundity is not as much as the channel thickness, then it will differ with Example of recurrence ward resistance 40 35 30 25 20 Resistance, Ohms 15 Tline parameter terms 10 5 0 0.E+00 1.E+09 2.E+09 3.E+09 4.E+09 5.E+09 6.E+09 Frequency, Hz R0 ~ resistance/unit length Rs ~ resistance/sqrt(freq)/unit length Interconnect: Adv

Microstrip Return Path Resistance The arrival current in the reference plane likewise adds to the recurrence subordinate misfortunes w t H (Current Density in plane) D The zone that the arrival current will stream in will permit a powerful width to be assessed Interconnect: Adv

Microstrip Return Path Resistance The present thickness formulae can be coordinated to get the aggregate current contained inside picked limits This demonstrates 79.5% of the current is contained in a separation +/ - 3H (W of 6H) from the conveyor focus Assuming an entrance of 1 skin profundity, the ground return resistance can be approximated as takes after Interconnect: Adv

Total Microstrip AC Resistance The aggregate resistance is roughly the total of the flag and ground way resistance This is an amazing "back of the envelope" recipe for microstrip AC resistance Interconnect: Adv

More correct Formula – Microstrip (From Collins) This equation was inferred utilizing conformal mapping procedures The recipe is not correct ought to just be utilized for appraisals Interconnect: Adv

1 µ I ( D ) + 2 1 ( D/H ) Stripline Losses In a stripline, the fields are referenced to two planes The aggregate current will be disseminated in both planes, and in the upper and lower bit of the flag conduit d For instance: In a symmetrical stripline,the zone in which current will travel increments by a variable of 2 and the resistance diminishes by an element of 2 This motivates the parallel microstrip display Interconnect: Adv

Calculating Stripline Losses The skin impact resistance of a stripline can be approximated as takes after: where the resistances are ascertained from the microstrip formulae at the suitable statures w H2 t H1 Interconnect: Adv

Surface Resistance for Microstrip The surface resistance (Rs) is frequently used to assess the resistive properties of a metal Observation of AC misfortune conditions demonstrate the resistance is relative to the square base of Frequency Rs is a steady that scales the square root conduct Is brought about by the skin misfortune marvels Used in specific T-line models (i.e.,W-Element) Interconnect: Adv

Trace Tooth structure (4-7 microns) Skin-Depth Plane Surface Roughness modifies Rs The formulae exhibited accept an impeccably smooth surface The copper must be unpleasant so it will hold fast to the cover Surface unpleasantness can build the figured resistance 10-half and also recurrence reliance extents Increase the successful way length and abatements the zone Interconnect: Adv

Surface Roughness Effects Frequency Dependence Surface harshness is not a huge component until skin profundity approaches the tooth measure (ordinarily 100 MHz – 300 MHz) At high frequencies, the misfortune gets to be distinctly capricious from customary geometric question since it is intensely subject to an arbitrary tooth structure. No longer shifts with the base of recurrence – something else Interconnect: Adv

Example of Surface Roughness Measurements demonstrate that the surface unpleasantness may make the AC resistance go astray from F 0.5 Tooth Structure Interconnect: Adv

Dielectric Losses Classic model of dielectric misfortunes got from damped motions of electric dipoles in the material adjusting to the connected fields Dipoles sway with the connected time fluctuating field – this takes vitality Dielectric steady gets to be distinctly intricate with misfortunes PWB load up producers indicate this was a parameter called "Misfortune Tangent" or Tan d The genuine part is the common dielectric consistent, the fanciful segment speaks to the misfortunes, or the conductivity of the dielectric Interconnect: Adv

Resin Material Glass Material Glass Weave Effects High Speed Signals Data demonstrates that Fiber Weave Effect can\'t be overlooked for High Speed signals Glass Weave Epoxy trough Weave Alignment Dielectric Constant Variation – from various specimen load up Trace Zo Interconnect: Adv

Transitional Single Line Differential Z odd Z diff 1 2 5 Vary 2 4.5 Loss, 1-|S(2,1)| 10 GHz Z diff Varies 5 GHz Trace Separation (mils) Current Distribution and Differential Losses Ports coordinated to diff. mode impedance Current dispersions impact the misfortune Evidence of a "sweet spot" where the misfortune is littlest Interconnect: Adv

Differential Microstrip Loss Trends - Tan d 0 tand=0.01 - 5 y = - 5E-10x - 1.2079 2 = 0.9953 R - 10 tand=0.03 Loss, dB - 15 y = - 1E-09x - 1.1925 2 R = 0.9992 - 20 - 25 0 5 10 15 20 25 Frequency, GHz Microstrip misfortunes as an element of recurrence and misfortune digression accepting smooth conductor (5/5/5; Circuit on page x) Model demonstrates straight conduct past 2.5 - 4 GHz Interconnect: Adv

Low Freq. Differential Loss Trends - Spacing W/S/W=5/15/5 Curves Intersect W/S/W=5/5/5 Losses