PCB Layout Notes

Created By: Hussein Nosair

Source: Polygons Pours & Copper Regions

* A copper pour on a signal layer is a common part of a PCB design.

* Hatched pour is used for ground plains in an analog design.

* Solid pour is used for carrying heavy currents.

* Solid pour is also used for ground plains meant for EMC shielding.

Glossary 2 :: SIDACTOR

Created By: Hussein Nosair

VDRM (Peak Off-state Voltage) : Maximum voltage that can be applied while maintaining OFF state.

IDRM (Leakage Current) : Maximum peak OFF-state current measured at VDRM (Peak OFF-state Voltage).

VS (Switching Voltage) : Maximum voltage prior to switching to ON state.

IS MAX (Switching Current) : Maximum current required to switch to ON state.

VT MAX (ON state Voltage) : Maximum voltage measured at rated ON state current.

IH MIN (Holding Current) : Minimum current required to maintain ON state.

CO MIN (Minimum OFF-state Capacitance) : Minimum capacitance measured in OFF state.

CO MAX (Maximum OFF-state Capacitance) : Maximum capacitance measured in OFF state.

IPP (Peak Pulse Current) : Maximum rated peak impulse current.

ITSM (Peak One-cycle Surge Current) : Maximum rated one-cycle AC current.

di/dt MAX (Rate of Rise of Current) : Maximum rated value of the acceptable rate of rise in current over time.

Switch to ON STATE :

V <= VS @ I <= IS MAX

Maintain ON STATE :

Von <= VT MAX @ Ion >= IH MIN

OFF STATE :

V <= VDRM @ I <= IDRM

Glossary 1

Created By: Hussein Nosair

VDRM = maximum repetitive peak-off state voltage
VRRM = maximum repetitive peak reverse voltage
ITGQM = maximum repetitive controlable on-state current
Cs = snubber capacity
IT(RMS) = RMS on-state current
ITAVm = maximum average on-state current (50 Hz half sine wave)
ITSM = maximum surge on-state current, nonrepetitive (50 Hz half sine wave)
(diT/dt)cr = critical rate of rise of on-state current
(dvD/dt)cr = critical rate of rise of off-state voltage
I2t = maximum rated value I2t
VTM = peak on-state voltage
VTO = threshold voltage
rT = slope resistance (on-state)
IGT = gate trigger current
VGT = gate trigger voltage
tGQ = turn-off time
TjM = maximum junction temperature
Tj = junction temperature = TjM unless otherwise indicated
Tc = case temperature
m = mass
Fp = pressure force

PCB Design Guidelines

Electrical Design Factors

Conductor Capacitance

C = 0.31 a/b + 0.23(1 + k) log10 (1 + 2b/d +2b + b²/d²)

Where
k = Substrate dielectric constant
a = Conductor thickness
b = Width of conductor in inches
d = Distance between conductors in inches

Conductor Resistance

R = 0.000227W

Where
W = Width of conductor

Characteristic Impedance

Zo = R + jwL / G + kwC

Where
Zo = Apparent Z of an infinitely long line in ohms
R = Resistance in ohms
L = Inductance in Henries
G = Conductor per unit length of line in mhos
C = Capacitance in farads

Characteristic Impedance for a Micro Strip

Zo = (h/W) (377 / (Sqrt. e_r) {1 + (2h/PI W)[1 + ln(PI W/h)]}

Where
h = Dielectric thickness
W = Micro Strip width
e_r = Effective dielectric constant of substrate

Switching-Mode Power Supply Design Tutorial

A switching-mode power supply is a power supply that provides the power supply function through low loss components such as capacitors, inductors, and transformers — and the use of switches that are in one of two states, on or off. The advantage is that the switch dissipates very little power in either of these two states and power conversion can be accomplished with minimal power loss, which equates to high efficiency. The term switchmode was widely used for this type of power supply until Motorola, Inc., who used the trademark SWITCHMODE TM for products aimed at the switching-mode power supply market, started to enforce their trademark. Then more generic terms had to be found. I started using the term switching-mode power supply to avoid infringing on the trademark. Others used the term switching power supply, which seems to be the more popular term. PSMA does not define either switching-mode power supply or switching power supply, but does define switching regulator.

Switching-mode power supply design tutorial by Jerrold Foutz