Differences between Normal Diode Schottky diode zener diode and avalanche Diode

Differences between Normal Diode , Schottky

diode , zener diode and avalanche Diode.

A diode is a commonly used semiconductor , that acts as one way gate to the flow of electrons.

DIODE

i.e; it allows current to pass in one direction only.A pn-junction diode is formed by joining together n-type and p-type silicon.

When the anode and cathode of a pn-junction diode are connected to external voltage such that the potential at anode is higher than the potential at cathode , the diode is said to be forward biased. In a forward-biased diode current is allowed to flow through the device when the forward voltage is greater than forward breakdown voltage.forward voltage drop depends on the material in which it is constructed.

 When potential at anode is smaller than the potential at cathode, the diode is said to be reverse biased. In a reverse-biased diode current is blocked.

 Consider the below case

Switching cases

In first case the diode is forward biased. Since the voltage

Voltage@A>Voltage@B=Forward Biased

so what if the voltage at point B is increased to a level greater than point A.Diode will turn to Reverse Bias

voltage@A<Voltage@B=Reverse Bias

And if again the voltage at point B is reduced to a level less that voltage at point A.Diode will switch to Forward bias.

Voltage@A>Voltage@B=Forward Biased

so what if i increase the speed of this switching !!! 

A Normal diode will not be able to handle this high speed switching's and here comes the ROLE of Schottky Diodes.

Schottky Diode

Schottky diodes has higher switching rates ie they can turn ON and turn OFF very rapidly compared to other types of diodes.

it also have an advantage of having less forward breakdown voltage, normally in the range of .2 to .5V .Because of these features, they are widely used in high speed switching designs. especially in DC-DC converters.

As their switching speed is very high, Schottky diodes recover very fast when the current reverses, resulting in only a very small reverse current overshoot. 

Diode Symbols

	Forward voltage drop	Reverse Voltage drop
Normal Diode	.3 to 1.1V	50V+
Schottky Diodes	.2 to .4V	20V-40V
Zener Diodes	.3 to 1.1V	1.8V-200V

Zener diode is similar to normal diode but has a wide range of Reverse breakdown voltages . above that voltage zener will breakdown and starts conducting . it is widely used for protection by connecting it in reverse bias.

Zener diode

As the name says for zener diode in reverse bias zener breakdown is happening and in the case of Avalanche diode Avalanche breakdown is happening.

Avalanche diodes are also used for circuit protection. When the reverse bias voltage starts to increase, the diode intentionally starts an avalanche effect at a predetermined voltage. This causes the diode to start conducting current without damaging itself.

Avalanche type diodes can result in increased reliability in many applications, particularly those where voltage transients are expected.  

Due to its high speed and ability to withstand large numbers of transients, avalanche diodes are used to protect circuits against surges, lightning and other transients.  They are faster than MOV’s, zeners, and gas tubes.

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MICROCHIP TO ACQUIRE ATMEL CORPORATION

Microchip Technology agreed to acquire a fellow chipmaker, the Atmel Corporation, for about $3.6 billion.

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SELECTION OF MICRO-PROCESSOR/SOC FOR CUSTOM EMBEDDED BOARD DESIGNS

10 POINTS TO TAKE CARE WHILE SELECTING THE MICRO-PROCESSOR/SOC for CUSTOM EMBEDDED BOARDS

Micro controller/Microprocessor is like heart of Every Embedded hardware Boards. For Low End boards it might be just a micro controller and for higher platform it will be microprocessors/FPGA. Some of the Examples for micro controllers are : MSP430G2 Series of Texas instruments , Atmega series of Atmel and PiC series of Micro chip.

Freescale, ST, TI, SiLabs, Atmel are the main vendors of high End Micro-processors.choosing the best is one of the toughest decision for an Embedded hardware design engineer.Here in this post i will explain the selection criteria's for choosing a microprocessors/controllers/soc in embedded hardware system.

• Point 1 : Use Dedicate controllers according to Application .

So First selection criteria is based on system application 

ie .if the application is communication there should be required communication interfaces or if it is a video processing/display based applications, support of GPU is also important. 

• Point 2 : Check whether the Microprocessor/SOC supports required Hardware Peripherals.

Hardware peripherals are -GPIO's,SPI,IIC,CAN,USB,ETHERNET,LCD etc. the requirement of hardware peripherals can be obtained by drawing a system level BLOCK diagram. 

• Point 3 : Memory Support

Estimate the memory size required for the application and ensure that it will be supported by the Microprocessor/SOC. it is also important to check the type of memory technology that supports the Microprocessor/SOC . like some Microprocessor/SOC doesn't support DDR memories . 

• Point 4 : CORE Parameters

1. Core Frequency : it is an important factor while choosing Microprocessor/SOC .Clock frequency is the internal clock speed in which the core operates .
2. MIPS : it is the count of instructions in millions executed per second.
   MIPS=count/time *10^6MIPS=Frequency/No of clock *10^6
3. BUS Throughput : Amount of data a processor can process in a certain time . it depends on the bus latency ,Bus width and the bus frequency.
4. Data Bus width : comes in 8 bit / 16 bit and 32 bit . when data bus width increases amount of data processing also increases ie. BuS Throughput increases .
5. Cache size : it is smaller but kind of faster memory in which frequent operated instructions are stored in cache .

• POINT 5 :Power consumption 

Power consumption is an important factor in battery operated applications . there are lot of Microprocessor/SOC with different technologies used to reduce energy consumption. most of the Microprocessor/SOC will have low power modes ,sleep modes etc . PMIC is an advanced power regulator for TI based Microprocessor/SOC.

• POINT 6 : Development & Debugging

 Availability of debugging tools and development IDE is also a main criterion while choosing the Microprocessor/SOC .J links[JTAG] is example for debugging tool for Atmel controllers . XDS 100/200/xx[JTAG] are examples for debugging tools for ti Microprocessor/SOC .

 Development IDE : example TI Code composer studio

J LINK

• POINT 7 : Availability & EOL

 Make sure that the selected processor is available in stock and will not get EOL in near future . 

• POINT 8 : Cost per Unit 

Cost of the Microprocessor/SOC should also be consided while making the selection, especially for large productions. 

• POINT 9 : DESIGN Support

It is the most important criteria while choosing Microprocessor/SOC .because support from manufactures will be required for resolving the issues happening in the development. Manufacture can support by providing reference designs,Technical documents,device drives ,Development boards etc.

Beagle Bone-AM335x development Board

• POINT 10 : Availability of required packages 

Ensure that the required packages are available for the selected Microprocessor/SOC and are in stock.

Thank you for Reading -AJ

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Interfacing Bluetooth Module with MSP430 Launchpad

Interfacing Bluetooth Module with MSP430 Launchpad

Here is the interfacing of a cheap Bluetooth module with MSP430 Lauchpad.
Bluetooth Module has 5 Pins with a UART I/O.

1. Enable
2. RX  
3. TX
4. VCC----> 5V
5. GND---->Gnd

We are not connecting the Enable pin since it default Enabled.

• RX is connected to UART pin of MSP430G2553 -P1.0
• TX is connected to UART pin of MSP430G2553 -P1.1

VCC is connected to 5V output of MSP430 lauchpad and Ground to common Ground.

Pin Connecton

Interfacing of MSP430 Launchpad with Bluetooth module

Bluetooth Module

Make Sure your Jumper is connected in SW UART . Now it's time for Testing the setup.

Burn the below program :

IDE :- Energia 

Energia is an open-source electronics prototyping platform started by Robert Wessels in January of 2012 with the goal to bring the Wiring and Arduino framework to the Texas Instruments MSP430 based LaunchPad. The Energia IDE is cross platform and supported on Mac OS, Windows, and Linux.

Program :

byte ehw = 0; // incoming serial byte

void setup()

{

  // start serial port at 9600 bps:

  Serial.begin(9600);

}

void loop()

{

  // if we get a valid byte, read analog ins:

while (!Serial.available() > 0)

    ehw = Serial.read();

   Serial.println(ehw);

   delay(10);

  }

After burning open the serial monitor.

Download the Android  APP 

EmbeddedHw

Android App from EmbeddedHW.com

• Click on the Home Button

Home screen of EmbeddedHw Android App

•  Turn On the Bluetooth of the smartphone & Pair the device (password:1234)
•  Click on the connect button and select our device.
•  Now click any of the buttons in the App home screen and verify whether any data is coming in the serial monitor of Energia. 

If everything works well , a data corresponding to each buttons will be shown in the serial monitor.

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Control 230V Devices Using Micro-Controller MSP430

Control 230V Devices Using Micro-Controller MSP430

Micro Controller Used :- MSP430G2553
Programming IDE        :- ENERGIA
Programmer                  :-Launchpad


Components Used :

LM317 - Linear Voltage Regulator

Micro-controller - MSP430G2553

Resistors -
R1-470ohm
R2-1k
R3-47k
R4-1K

Relay - 12V

Transistor-BC 548

12v Power Source

Micro-controller circuit to control 230V devices

Here is a Micro-controller simple circuit which can control our home appliance using a relay circuit .To control more devices more relay units can be added to the other GPIO's .Transistor is used to switch the relay according to the input from the Controller.Power the device using a 12v source . the regulator LM317 will regulate the 12V input to Controller operational voltage .Given below an example program to light the device (ex:230v CFL ) every 5 minutes.Connect the launchpad and burn the below program to controller.

Example Program



void setup() {                
  
  pinMode(2, OUTPUT);     
}

// the loop routine runs over and over again forever:
void loop() {
  digitalWrite(2, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(300000);             // wait for 5 minte
  digitalWrite(2, LOW);    // turn the LED off by making the voltage LOW
  delay(300000);               // wait for 5 minte
}

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Linear voltage regulators v/s Switching regulators

Regulators used in Embedded HardWare Designs

Regulators are mainly classified in to two

1. Linear Voltage regulator
2. Switching regulators. 

LINEAR VOLTAGE REGULATOR

They are good for powering very low powered devices.it is not advised to use in High end applications Since it is regulating the voltage by taking the difference between the input and output voltages, and just burning it as heat.

Linear Voltage Regulator -7805

The larger the difference between the input and output voltage/larger the output current ,Power dissipated will also be high .so it is recommender to use suitable Heat sinks according to the use.
Even the new LDO (low drop-out) regulators are also inefficient linear regulators - they just give you more flexibility with input voltage drops.

Power consumption is very important in embedded hardware boards. Due to this inefficiency of linear voltage regulators they are rarely used in High end applications.But still LDO is a better choice than a normal linear voltage regulator

Examples for Linear voltage regulators :

                           Low current fixed voltage regulators:

                                         5V 1 A - 7805
                   12V 1A - 7812

                          Low current Variable voltage regulator:

                                      3~28V 1A -LM317

                           For High current Variable Voltages

                                          3~28V  5A - LM338


SWITCHING REGULATORS

A switching regulator works by taking small chunks of energy, bit by bit, from the input voltage source, and moving them to the output. This is accomplished with the help of an electrical switch and a controller which regulates the rate of switching . ie it controls the amount of energy transferred to the output.Switching regulators are complex circuits to design, and as a result they aren’t very popular with hobbyists.

The energy losses in Switching regulators is very small , which gives an efficiency of 80-95%. Since their efficiency is less dependent on input voltage, they can power useful loads from higher voltage sources.

Given below is Switching regulator which can be helpfull for hobbyists

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SIGNALS TERMINATIONS

SIGNAL-BUS-CLOCK TERMINATIONS In Embedded HARDWARE DESIGNS

There are two type of terminations

1.  Source Termination -Near Source
2.  End Termination -Near Receiver

Source termination works differently than end termination, but the net effect is the same. It works by controlling signal reflections, not preventing the reflections in the first place. Because of this, it only works if a driver output is feeding a single load.

The huge benefit of source termination is that it does not load down the driver like end termination does. 

SERIES TERMINATION :

Most drivers have some resistance on it's output. That resistance is usually in the 20-30 ohm range. The sum of the output resistance of the driver and your resistor must equal your trace impedance in series termination.Source Termination may effect the rise time of the signal because of the RC time constant ie. Resistance of termination and capacitance of cable . 

SERIES TERMINATION

Reducing rise time will reduce the demand at the driver side which reducing the Instantaneous current demand on the driver [reducing ground bounce and EMI].A series terminated line does not stop reflections but reduces the amplitude of the ringing. If a source resistor is used with multiple loads, only the last device will see a cleaner edge.

OUTPUT RESISTANCE + TERMINATION RESISTANCE = TRACK IMPEDANCE

A reflection will occur when the termination resistor does not match the trace impedance 

Parallel Trace Termination :

PARALLEL TERMINATION

In  parallel termination a resistor is connected to the ground or VCC parallel to I/O.Power dissipation is high during the operations at lower frequency ie. at lower switching rates .

TERMINATION RESISTANCE = TRACK IMPEDANCE

A reflection will occur when the termination resistor does not match the trace impedance .

INSTRUCTION WHILE PROBING THE SIGNAL

When checking signals on Scope you must probe at the receiver. Probing anywhere else will likely give you a distorted waveform and trick you into thinking that things are worse than they really are. Also, make sure that your ground clip is as short as possible.

Will include Differential pair terminations in next articles..

GooD LucK - AJ

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