PCB Design Practical Design Guidelines http sercpitt weebly

PCB Design Practical Design Guidelines http: //sercpitt. weebly. com/

PRELIMINARY DESIGN QUESTIONS 2

Important Datasheet Info • Pinout and Pin Orientation • Package Size and Type • Power Rating • Soldering Temperatures • Recommended Configurations 3

Protection Devices Voltage Arresters Fuses Mechanical Protection Reverse Bias Protection ESD Protection EMI Protection 4

Power Generation • Switching Converters • Linear Regulators 5

PCB DESIGN GUIDELINES 6

Key Principles • How current flows through the board and its return pathway to ground with changes in frequency. • Traces can cause unwanted inductance or capacitance depending on how they are laid out. • Electric and magnetic field coupling and its propagation around traces and planes and how these fields couple into surrounding traces/planes. • Amount of current and voltage that is on traces and how that changes the propagation of the EM fields from the trace or how the trace is affected by outside radiation. The smaller the signal on the trace the more susceptible to outside radiation it is. While a high current or very large signal can cause very large EM wave propagation that creates noise on surrounding ground planes and traces. 7

Current Flow 8

Coupling • Inductive • Capacitive 9

PCB Stackup Goals 1. A signal layer should always be adjacent to a ground or power plane. This means placing the ground or power plane one layer below or on the same layer as the trace is being run. This allows for return current to be as close to the source as possible. 2. Signal layers should be tightly coupled to their adjacent planes. This means keeping the ground plane close to the signal plane either above or below. 3. Power and Ground planes should always be closely coupled together. This means placing the planes within one or two layers of each other. 4. High speed signals (>500 MHz) should be routed on buried layers located between planes. In this way the planes can act as shields and contain the radiation from the high speed traces. 5. Multiple ground planes are very advantageous, since they will lower the ground (reference plane) impedance of the board and reduce common mode radiation. 10

Two Layer Stackup 11

Four Layer Stackup 12

Routing Traces 13

Vias 14

Copper Pours 15

Grounding 16

Decoupling Capacitors: Poor 17

Decoupling Capacitors: Better 18

Decoupling Capacitors: Best 19

Component Selection • Resistors • Capacitors • Inductors • IC’s: Surface Mount vs. Through Hole 20

Circuit Mounting 21

Layout Programs • Express. PCB Intro Tutorial: http: //home. wlu. edu/~ericksonj/engn 208_w 2015/hw/express. P CBtutorial. pdf • Eagle Intro Schematic Tutorial: https: //learn. sparkfun. com/tutorials/using-eagle-schematic • Eagle Intro PCB Tutorial: https: //learn. sparkfun. com/tutorials/using-eagle-board-layout • Altium Intro Tutorial: http: //techdocs. altium. com/display/ADOH/Tutorial++Getting+Started+with+PCB+Design# • Mentor Graphics Pad Intro Tutorial: https: //engineering. purdue. edu/ece 477/Archive/2011/Spring/S 1 1 -Grp 07/nb/datasheets/pads_tutorial_2_rev. pdf 22

PCB Ordering Manufactures Components • Sunstone: http: //www. sunstone. com/ • Digikey: https: //www. digikey. com/ • Mouser: http: //www. mouser. com/ • Advanced Circuits: http: //www. 4 pcb. com/ • Jameco: http: //www. jameco. com/ • Sparkfun: https: //www. sparkfun. com/ • Adafruit: https: //www. adafruit. com/ • Arrow: https: //www. arrow. com/ • Express. PCB: https: //www. expresspcb. com/ 23