Post on 07-Apr-2018
transcript
8/6/2019 Lesson 3 - Electrical Design Considerations
1/32
Electrical Design Considerations
8/6/2019 Lesson 3 - Electrical Design Considerations
2/32
Electric component
Any device that handles electricity
8/6/2019 Lesson 3 - Electrical Design Considerations
3/32
Passive Components
Contributes no power gain
No control action
Does not require any input other than a signalto perform its function
Gain < 1
8/6/2019 Lesson 3 - Electrical Design Considerations
4/32
Examples:
Resistors
Capacitors
Inductors
8/6/2019 Lesson 3 - Electrical Design Considerations
5/32
Active Components
Capable of controlling voltages or currents
Can create a switching action in the circuit
Amplify or interpret a signal
8/6/2019 Lesson 3 - Electrical Design Considerations
6/32
Examples:
Diodes
Transistors
ICs
8/6/2019 Lesson 3 - Electrical Design Considerations
7/32
Discrete
Integrated Circuit
8/6/2019 Lesson 3 - Electrical Design Considerations
8/32
Discrete
Component packaged with one or twofunctional elements
8/6/2019 Lesson 3 - Electrical Design Considerations
9/32
Integrated Circuit
Combination of several interconnected discretecomponents
Packaged in a single case to perform multiple
functions
8/6/2019 Lesson 3 - Electrical Design Considerations
10/32
Through-hole
Surface Mount
8/6/2019 Lesson 3 - Electrical Design Considerations
11/32
Through-hole
Have leads that can be inserted through mountingholes
Surface Mount
Attached directly on the surface of the board
8/6/2019 Lesson 3 - Electrical Design Considerations
12/32
Component Leads
Axial leads
Two leads, extending from each side of thecomponent
Radial leads
Leads emanate from the bottom of the component
8/6/2019 Lesson 3 - Electrical Design Considerations
13/32
Single in-line
Dual In-line
Pin-grid array
Leadless components
8/6/2019 Lesson 3 - Electrical Design Considerations
14/32
Conductor Dimensions
Conductor width
Component packing density
Minimum spacing between conductors and
components Geometrical constraints due to component outlines
8/6/2019 Lesson 3 - Electrical Design Considerations
15/32
Resistance
Capacitance
Inductance
8/6/2019 Lesson 3 - Electrical Design Considerations
16/32
Resistance
Measure of how strongly a material opposesthe flow of electric current
8/6/2019 Lesson 3 - Electrical Design Considerations
17/32
8/6/2019 Lesson 3 - Electrical Design Considerations
18/32
Resistance of conductor
Depends on the specific resistivity of copper
@ 20oC 1.724x10-6 ohm-cm
@ 25oC
1.78x10
-6
ohm-cm
8/6/2019 Lesson 3 - Electrical Design Considerations
19/32
Assume:
Standard copper foil of 35 um thickness (withoutplating)
R = L / A
8/6/2019 Lesson 3 - Electrical Design Considerations
20/32
Example 1
Compute the resistance of a 1mm wide copperconductor per cm length at 20oC
8/6/2019 Lesson 3 - Electrical Design Considerations
21/32
Example 2
Compute the resistance of a copper conductorat 25oC with a 0.3 mm conductor width and35um copper thickness and 500 mm length
8/6/2019 Lesson 3 - Electrical Design Considerations
22/32
Example 3
Compute the resistance of an 8 mil wide copperconductor with a length of 120 mm and acopper thickness of 70 um. Assume thetemperature to be 25oC
8/6/2019 Lesson 3 - Electrical Design Considerations
23/32
Resistance and Temperature
When a current flows through a conductor, itstemperature rises due to the joule effect
Rt= R
0[1 + (T
1-T
0)]
8/6/2019 Lesson 3 - Electrical Design Considerations
24/32
Example 1
Assume that the inside temperature in anelectric equipment is 80oC while the outsidetemperature is 20oC. Compute the resistanceat 80oC given copper conductivity of 0.0039, theresistance of 0.5mm conductor, 10 cm long(with 100 ohm resistance)
E l 2
8/6/2019 Lesson 3 - Electrical Design Considerations
25/32
Example 2
Rt= 2.706x10-8
= 0.0043
T1 = 25
o
C T
2= 20oC
Recommended Current Carrying
8/6/2019 Lesson 3 - Electrical Design Considerations
26/32
Recommended Current CarryingCapacity of Traces
8/6/2019 Lesson 3 - Electrical Design Considerations
27/32
C it
8/6/2019 Lesson 3 - Electrical Design Considerations
28/32
Capacitance
Ability of a body to hold electrical charge
2 situations:
Capacitance between conductors on opposite sides
Capacitance between adjacent conductor
Capacitance between conductors
8/6/2019 Lesson 3 - Electrical Design Considerations
29/32
Capacitance between conductorson opposite sides of the PCB
C = 0.886 x x A/b
relativedielectric constant
A totaloverlapping area
b thickness of
dielectric
Capacitance between adjacent
8/6/2019 Lesson 3 - Electrical Design Considerations
30/32
Capac ta ce bet ee adjace tconductors
Function of Width
Thickness
Spacing Dielectric constant of the board material
8/6/2019 Lesson 3 - Electrical Design Considerations
31/32
Coupling capacitance for a G-10 laminate withdielectric constant of 5.4 and conductorthickness of 35um
8/6/2019 Lesson 3 - Electrical Design Considerations
32/32