PLEASE GIVE THE FULL DETAILS OF THE STEPS ON EACH QUESTIONS SO I COULD FOLLOW UP

Question

PLEASE GIVE THE FULL DETAILS OF THE STEPS ON EACH QUESTIONS SO I COULD FOLLOW UP YOUR WHOLE EXPLANATIONS.

PLEASE WRITE THE STEPS ON SOLVING THIS EXAMPLE

EX) STEP 1, STEP 2, ETC

HANDWRITING IS OKAY AS LONG AS IT IS READABLE.

IF YOU HAVE USED THE EQUATIONS OR CONCEPTS, PLEASE STATE IT CLEARLY WHICH ONE YOU HAVE YOU USED SO I COULD FULLY UNDERSTAND THE DETAILS OF THE STEPS YOU HAVE DONE.

PLEASE DO NOT OMIT THE DETAILS OF STEPS AND CONCEPTS YOU HAVE USED, CLEARLY STATE IT!!

aircuit when we are designing certain micro What itis usage? What other circuits do we need in order to proceed? Would you be able to give some advice when you are start from the beginning designing the whole PCB boards?

Explanation / Answer

Use of Clock Ciricuit in Microcontroller-:

The 'clock' is heartbeat of any processor.At a time one thing executes by processor.The time is given by the clock.The clock is just an oscillator running 0,1,0,1,0.....Each time the clock changes level,the processor executes one instruction according to clock.

Timing is everything in digital circuits.Without clocks digital circuit cannot run.Clock controls the input and output of the circuit and provide synchronisation for peripherals.

Why do we need Clock:-

There are circuits where we do not use clock at all.see asynchronous circuits.The main aim for using a clock is that it defines when to start the next step.if do not use clock then do not know which step will perform first and how it would be performed.

Example-

a=0;

c=0;

c=a+5;

c=a*5;

now if do all operations at once(i.e. without using clock)there is a possibility that c=a*5 might get excuted first and then c=a+5 will be excuted which gives wrong answer(they are basically flipflops which stores wrong values).There is a another possibility too what if c=0 is excuted at last.The values fo c gets changed completely.Hence microprocessor and microcontroller need clock.Without clock circuit is very complex and difficult.

Desinging of PCB Boards:-

(1) Sizing Traces:-Copper traces have resistance.This means trace has a voltage drop,power dissipation,a temperature rise when current flows through it.Resistance is defined by this formula-

R=(resistivity*length)/(thickness*width)

PCB designers mostly use thickness,length,width to control resistance of a PCB trace.Resistance is a physical property of the metal used to make the trace.PCB teace thickness is measured in ounces of copper,Use PCB trace width calculator to determine how thick and wide traces should be for application.Aim for 5 degree temperature rise.if have extra space on the board,use bigger traces.

When doing a multi layer board,traces on external layers have better cooling than traces on internal layers beacuse the heat from inner layers has to travel through layers of copper and PCB matarial before being conducted or connected.

(2)MakeloopsSmall:-

High frequency loops should be made as small as possible.small loops have lower inductance and resistance.Placing loops over a ground plane further reducesinductance.havinf small loops reduces high frequncy voltage spikescaused by

V=L di/dt.

(3) Decoupling capacitor Placement:-

Place capacitoe near to the power and ground pins of IC's to maximize decoupling efficiency.

(4)kelvin connectons:-

Itis used to reduce stray resistance and inductance.for example,kelvin connections for a current sense resistor are placed exactly at the ressior pad,not at arbitrary place on the traces.

(5) Keep Digital ad noisy traces away from analog traces:-

Parallel traces form a capacitor.placing traces close together capacitively couples the signals on te traces,if the signals are the hig frequency.Keep high frequency and noisy traces away from traces.

(6)Ground is not Ground:-

Ground is not an ideal conductor.Placing a ground plane directly under signal traces lowers the impedance of the traces,which is ideal.

(7) Size and Number:-

If routing a trace from one side to other side of PCBand need low resistance or inductance,use multiple vias.large vias have lower resistance.it is used for grounding filter capacitors and high current nodes.

(8)PCB as Heatsink:-

Extra copper place around surface mount component to provide extra surface area to dissipate heat more efficiently.

(9) Thermal Vias:-

Vias can be used tomove heat from one side of a PCB to the other side.

(10)Thermal Relief:-

It is making a connections between trace or a fill and component pin small to make soldering easier.it is a small connection is short to reduce te mpact on electrical resistance.if thermal relief not used then components may bea little cooler.

(11) Distance between traces and mounting Holes and use heat sensitive components.

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