Non Ideal Behavior of Components

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_2 Course outline Contents Digital Signal Model Non Ideal Behavior of ComponentsNon Ideal Behavior of Components High Speed Properties of Digital Gate Ground Planes Crosstalk Power Distribution Terminations Conductors Resistors Capacitors Inductors

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_3 Conductors Each wire or trace contains hidden parasitic inductances (capacitive effects are negligible) Wires, harnesses, PCB traces, component leads (Z = R + jX L ) –LF: resistive behavior (R > X L ) –HF: inductive behavior (X L > R) –VHF: antenna behavior (l > /20), where l = wire length

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_4 Conductors Example PCB trace of 10 cm: R  60 m , L  8 nH/cm X L  R for f = R/2  L  120 kHz Antenna for f > c/(20  l)  150 MHz Rule of thumb: –above audio frequencies, ground connections behave like inductors instead of being short circuits; –at radio-frequencies wires and traces behave like antennas and radiate electromagnetic waves

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_5 Resistors Different technologies –carbon (1) –resistive film (2) –wire-wound (3) Different behavior with frequency

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_6 Resistors Equivalent circuit –L: internal inductance, important for technology (3) –C P : internal and package capacitance, important for technology (1) –L L : lead inductance –C L : lead capacitance, important only in the GHz range LL CPCP CLCL R

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_7 Resistors Example n. 1 Carbon resistor –R = 1000  –L L = 14 nH –C P = 1.2 pF –L = 0 –C L = 0 –Frequencies f 1  MHz f 2  1.2 GHz Resonant frequencies

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_8 Resistors Resistive behavior Capacitive behavior Inductive behavior

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_9 Resistors Resonant frequencies Example n. 2 Carbon resistor –R = 100  –L L = 5 nH –C P = 1.2 pF –L = 0 –C L = 0 –Frequencies f 1  1.33 GHz f 2  2.05 GHz

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_10 Resistors Resistive behavior Capacitive behavior Inductive behavior

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_11 Capacitors Different technologies –tantalum (1) –ceramic (2) –electrolytic (3) Different behavior with frequency

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_12 Capacitors C ESLESR Equivalent circuit –ESL: equivalent series inductance, depends on lead length –ESR: equivalent series resistance, depends on capacitive losses (important for 3)

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_13 Capacitors Example –C = 470 pF –ESL = 14 nH –ESR = 3  –Frequency f r  62 MHz Resonant frequency

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_14 Capacitors Capacitive behavior Inductive behavior

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_15 Inductors Different technologies –wire-wound (1) –ferrite beads (2) Different behavior with frequency

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_16 Inductors L CWCW R Equivalent circuit for wire-wound technology –R: wire resistance –C W : capacitance between windings

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_17 Inductors Example –L = 15  H –C W = 4 pF –R = 5  –Frequencies f 1  53 kHz f 2  MHz Resonant frequencies

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_18 Inductors Capacitive behavior Inductive behavior Resistive behavior In practice, the use of real inductors is limited below  10 MHz

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_19 Inductors Equivalent circuit for the ferrite beads technology –R d : ferrite losses –C W : capacitance between windings L RdRd CwCw

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_20 Inductors Example –L = 15  H –C W = 0.04 pF –R d = 200  –Frequency f r  MHz Resonant frequency

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_21 Inductors The presence of ferrite extends the use of inductors to higher frequencies Inductive behavior

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_22 Packaging Take care of the choice of the component package –SMT (Surface Mount Technology): low parasitic effects –DIL (Dual In Line): V CC pin number 7 GND pin number 14 Radiation loop

@ Copyright F. Canavero, R. Fantino 7/6/2017Licensed to HDT - High Design TechnologyNIB_23 Next topic High Speed Properties of Digital Gates