SD Card Speed Rating...

The speed rating of an SD card is usually shown on the SD card itself as certain number. These numbers are certain classes which defines certain minimum speed performance levels. In order to pass a class, the card must exceed the minimum speed value for both read and write.The classes defined by SD Association is as follows :

Other than this , some type of SD cards are available with designation of Ultra High Speed (UHS) which has higher performance of  50MB/s for UHS-I , 100MB/s for UHS104, and even 312MB/s for UHS-II.

The choice of SD card thus solely lies in the application for which it is chosen as different application requires different speed :

• Class 2 for SD video recording
• Class 4 and 6 for HD ~ Full HD video recording,
• Class 10 for Full HD video recording and HD still consecutive recording
• UHS Speed Class 1 for real-time broadcasts and large-size HD videos

SPD EEPROM !!!

SPD or Serial Presence Detect EEPROM is the area where details and characteristics of memory module (DIMMs)  is written. This EEPROM in the contains timing parameters, manufacturer, serial number and other useful information about the module. This data allows a device utilizing the memory to automatically determine key parameters of the module.
The SPD EEPROM is accessed through SMbus ,a variant of I2C. Apart from this, it has separate power pins and three address selection bits (SA0-2), using which  a unique address in the range 0x50–0x57 can be assigned to the EEPROM.
For more information, see :
http://en.wikipedia.org/wiki/Serial_presence_detect

Class And Type of PCBs 

Board Class:(as per IEC6011)


Class I General Electronic Products:- Includes customer products,some computer peripherals suitable for applications where cosmetic imperfections are not important and the major requirement is function of the completed printed board .

Class II Dedicated Service Electronic Products - Includes communication equipment, sophisticated business machines ,instruments where high performance and extended life is required and for which uninterrupted service is desired and not critical . Certain cosmetic imperfections are allowed  .

Class III High reliability Electronic Products : - Includes the  equipment and products where continued performance or performance on demand is critical. Equipment downtime cannot be tolerated and must function when required such as in life support items or flight control systems Printed boards in this class are suitable for applications where high level of assurance and service is essential




Board Type(as per IEC6012A) : Printed boards without plated-through holes  and with plated-through holes  are classified as follows:


Type 1—Single-Sided Board
Type 2—Double-Sided Board
Type 3—Multilayer board without blind or buried vias
Type 4—Multilayer board with blind and/or buried vias
Type 5—Multilayer metal core board without blind or buried vias 
Type 6—Multilayer metal core board with blind and/or buried vias

Received signal strength indication (RSSI)

       In telecommunications, received signal strength indicator (RSSI) is a measurement of the power present in a received radio signal.

      RSSI is a generic radio receiver technology metric, which is usually invisible to the user of the device containing the receiver, but is directly known to users of wireless networking of IEEE 802.11 protocol family.

     In an IEEE 802.11 system RSSI is the relative received signal strength in a wireless environment, in arbitrary units. RSSI is an indication of the power level being received by the antenna. Therefore, the higher the RSSI number (or less negative in some devices), the stronger the signal.

Reference : http://en.wikipedia.org/wiki/Received_signal_strength_indication

Accuracy Class

Accuracy class tells the percentage error of an equipment.
For example, an Accuracy Class 1.0 CT means the error will be +/- 1 %. That means, say, you have a 100/5A CT and when you pass 100A through the primary of this CT, the secondary current can be anywhere between 4.95A to 5.05A.
The accuracy class stating the limits of permissible error is expressed as a percentage of the span.
The following accuracy classes are defined: 0.1, 0.25, 0.6, 1,1.6, 2.5 and 4.

Accuracy class Limits of permissible error                       (percentage of span)

0.1                                                                                     ± 0.1 %
0.25                                                                                   ± 0.25 %
0.6                                                                                     ± 0.6 %
1                                                                                        ± 1 %
1.6                                                                                     ± 1.6 %
2.5                                                                                     ± 2.5 %
4                                                                                        ± 4 %

Parameters for Effective Circuit Protection Using TVS

A good TVS device for protecting dataline communications interfaces must have some key parameters. 

First, low working voltage is a critical TVS parameter for safeguarding submicron integrated circuits. The working voltage, or Vrwm, is the maximum rated DC voltage for the TVS device. At the Vrwm voltage, the TVS is still a non-conducting device. Once the transient voltage rises above the working voltage, the TVS quickly achieves breakdown and presents a low impedance  path to divert the transient. Thus, a low working voltage is essential for clamping a transient to a level well below the damage threshold of the IC that the TVS is protecting. The I-V curve illustrates the advantage of a lower working voltage. The green line represents a typical  I-V curve for a standard TVS device. The lower working voltage means the transient voltage is arrested more quickly and thus can be clamped to a lower voltage. Using TVS devices with lower working voltage is critical to reducing the stress energy seen by the communications transceiver. 

Secondly, the TVS should present low capacitance to preserve signal integrity on the high-speed interface. If the capacitance of the TVS diodes is too high, adding excessive loading to the circuit, signal distortion and data errors will result.

Finally, the TVS needs to offer high-surge handling. For systems in the communications infrastructure, components rated only for ESD transient levels will not provide sufficient protection. The TVS component must also be able to handle the higher energy contained within cable discharges and the variety of lightning threats. As a general guideline, the TVS should at least provide 25A of surge handling for an 8x20 microsecond pulse. 

What is EMI and EMC ?

• An electromagnetic disturbance which may degrade the performance of an equipment (device, system or sub-system) or causes malfunction of the equipment, is called electromagnetic interference (EMI).

• Electromagnetic compatibility (EMC) is a near perfect state in which a receptor ( device , system or subsystem) functions satisfactorily in common electromagnetic environment, without introducing intolerable electromagnetic disturbance to any other devices / equipments / system in that environment.

Board Zoning

Board zoning has the same basic meaning as board floor planning, which is the process of defining the general location of components on the blank PCB before drawing in any traces. Board zoning goes a little bit further in that it includes the process of placing like functions on a board in the same general area, as opposed to mixing them together (see Figure). High-speed logic, including micros, are placed close to the power supply, with slower components located farther away, and analog components even farther still. With this arrangement, the high-speed logic has less chance to pollute other signal traces. It is especially important that oscillator tank loops be located away from analog circuits, low-speed signals, and connectors. This applies both to the board, and the space inside the box containing the board. Do not design in cable assemblies that fold over the oscillator or the microcomputer after final assembly, because they can pick up noise and carry it elsewhere. 

In prioritising component placement, the most important things to do in PCB design are:

• Locate the microcomputer next to the voltage regulator, and the voltage regulator next to where  the input power enters the board.


• Built a gridded or solid ground between the three 

Zarro boogs

By design, Bugzilla is programmed to return the string "zarro boogs found" instead of "0 bugs found" when a search for bugs returns no results"Zarro Boogs" is a facetious meta-statement about the nature of software debugging. Bug tracking systems like Bugzilla readily describe how many known bugs are outstanding. The response "zarro boogs", is intended as a buggy statement itself (a misspelling of "zero bugs"), implying that even when no bugs have been identified, software is still likely to contain bugs that haven't yet been identified.

The following comment is provided in the Bugzilla source code to developers who may be confused by this behaviour:

Zarro Boogs Found

This is just a goofy way of saying that there were no bugs found matching your query.

So when you query for a list of bugs, and it gets no results, you can think of this as a friendly reminder. Of *course* there are bugs matching your query, they just aren't in the bugsystem yet...

http://en.wikipedia.org/wiki/Zarro_boogs?useFormat=mobile#Zarro_boogs

Via Types

Through via : An interconnection between the top and the bottom layer of a PCB. Through vias can also provide interconnections to inner PCB layers.

Blind via : An interconnection from the top or bottom layer to an inner PCB layer.

Embedded via: An interconnection between any number of inner PCB layers.

Figure shows all three via types.

Different types and Terminology of LCD

Two common types of LCD are
1.Transmissive LCD
The Transmissive LCD is illuminated from one side and viewed from the opposite side.
Activated cells appear dark and inactive cells appear bright. One disadvantage of
Transmissive LCD is that lamp used to illuminate the LCD consumes more power than
consumed by the LCD itself.
2. Reflective LCD
This is commonly used in pocket calculators and digital watches. It is viewed by ambient
light reflected in a mirror behind the display. They have lower contrast than the
Transmissive type, because the ambient light passes twice through the display before
reaching the viewer. The advantage is that there is no lamp to consume power, so the
battery life is long.

Following link describes the terms normally used for LCD

http://www.pacificdisplay.com/lcd_glossary.htm

Why DDR3 handling More Bit rates!!!!

Why DDR3 is handling higher bit rates(>600Mhz)!!.Answer of that question is very simple.DDR3 is embedded with an 8-Bit prefetch module. Because of this 8-bit early prefetch Internal modules require lesser frequency to achieve Higher data rate.

Charging lead acid batteries

The different charging techniques for charging lead acid batteries are :

Constant Voltage Charging:  This method is the most commonly used for SLA batteries as the individual cells tend to share the voltage and equalize the charge between them. It is important to limit the initial charging current to prevent damage to the battery. However, with a single fixed voltage, it is impossible to properly balance the requirements of a fast charge cycle against the danger of overcharge.

Constant Current Charging:  This method can be used for a single 2 V cell but is not recommended for charging a number of series connected cells, a battery, all at the same time. This is because some cells will reach full charge before others and it is very difficult to determine when the battery has reached a fully charged state. If the charge is continued at the same rate, for any extended period of time, severe overcharge may occur to some cells, resulting in damage to the battery.

Taper Current Charging:  This method is not really recommended for charging SLA batteries as it can often shorten battery service life due to poor control of the final fully-charged voltage. However, because of the simplicity of the circuit and subsequent low cost, taper current charging is often used to charge a number of series connected batteries that are subject to cyclic use. When using this method it is recommended that the charging time is either limited or that a charging cut-off circuit is incorporated to prevent overcharge.

Using a combination of the constant current charging and two-stage constant voltage charging techniques and also by monitoring the battery terminal voltage and temperature a multi-stage charge profile can be implemented to reduce stress on the battery while giving the shortest possible charge time.

The first part of the multi-stage charge cycle is constant current mode Bulk Charge which limits current to a maximum of 0.25C Amps (where C = battery capacity, so 0.25C is a quarter of the battery capacity), as required by SLA batteries. For example, if the capacity of the SLA battery being charged is 4 A-hr, then the constant current should be limited to 1 A. During this stage, the battery terminal voltage is monitored until the terminal voltage reaches 14.4 V (2.40 V/cell).

Once the terminal voltage reaches 14.4 V the charge cycle automatically moves on to the second stage High Absorption Charge.  output changes from constant current to constant voltage and now monitors the charge current. When the charge current drops to 0.05C A, which is 0.2 A for a 4 A-hr battery, the battery will have recovered approximately 70 - 80% of its charge.  At this point the output voltage reduces to 13.65 V (2.275 V/cell) : this is the Low Absorption Charge. The remaining 20 - 30% of the charge is carried out at this lower voltage in order to prevent overcharge. 
The final stage of the charge cycle is the Float Charge.

Hysteresis in Digital or Analog Devices or IC's

Hysteresis the word it self explain the meaning!!!Hysteresis means the lagging of an effect behind its cause!!.If you are familiar with the digital design,you would definitely gone through the data sheets of Digital ICs with some Input hysteresis values say 200mV.What it does actually meant for? the answer is simple

Let say you detect a Low to high transition at 1.8V(Vref).A 200 mV Hysteresis would mean that your device will detect the Low to high transition at 1.9V and the High to low transition locked at 1.7V.This voltage lag between activating and deactivating the device is known as the Hysteresis of the system.Hysteresis is ensure to avoid several noise transitions would cause the H-L and L-H transitions of the device.So a 200mV Hysteresis means that noise levels lesser than 200mV wont give any disturbance to the Vref of your system..

HSCSD

HSCSD

    While we are using Mobile GPRS , there would be an [E] or a [G] indicating whether it is using EDGE (Enhanced Data rates for GSM Evolution) (2.5G) or GPRS (General Packet Radio Service)(2G) is used for data transfer . But very rarely do we see an [H]. [H] indicates HCSD

      HSCSD (High Speed Circuit Switched Data) enables data to be transferred more rapidly than the standard GSM (Circuit Switched Data) system by using multiple channels. The maximum number of timeslots that can be used is four, giving a maximum data transfer rate of 57.6 kbps (or 38.4 kbps on a GSM 900 network). HSCSD is more expensive to use than GPRS, because all four slots are used simultaneously - it does not transmit data in packets. Because of this, HSCSD is not as popular as GPRS and is being replaced by EDGE.

        So don't be perplexed if you see an  [H] displayed on your phone while using GPRS. For more details look in the links given below

http://en.wikipedia.org/wiki/General_Packet_Radio_Service

http://www.mobile-phones-uk.org.uk/gprs.htm

Precharging of DRAM's

After the data is being fetched from the memory,a command called precharge needs to be given.This will close the current memory row address that was being used and allowing a new row address to be activated for the next data fetch.From the DRAM point of view this command is known as RAS Precharge.The time taken between the precharge command and the next active command(Read or write Command) issued is known as RAS precharge time(Trp).This time will affects the speed performance of the DRAM.So lesser time might cause Greater speed performance.

Modes of Fiber

You may heard about single Mode fiber and Multi Mode fibers.Modes of a fiber doesn't means that the number of frequencies supported by the fiber but it actually defines how the wave distributed in space or orientation of data wave inside the Fiber.More clearly, a single mode fiber will transmit different frequency data waves in a path parallel to the axis.Multi-mode fiber's will be used for to transmit different frequency waves in different paths/spacial paths.Don't be confused with the Wavelength used for the data transmission, a wave with definite wavelength is being used as a carrier for the different frequency data packets.For example 1300 nm Optical carrier will contains multiple frequency data and also same frequency data would be oriented differently in multi-mode fiber.

SEPIC..

Single-Ended Primary-Inductor Converter(SEPIC) is a type of DC-DC converter in which the input voltage is allowed to vary above and below the regulated output voltage. SEPICs are useful in applications in which a battery voltage can be above and below that of the regulator's intended output.

Details of this type of converter is given in the following links..

http://www.ti.com/lit/an/slyt309/slyt309.pdf

http://www.switchingpowermagazine.com/downloads/Sepic%20Analysis.pdf

VSWR..

When a transmission line (cable) is terminated by an impedance that does not match the characteristic impedance of the transmission line, not all of the power is absorbed by the termination. Part of the power is reflected back down the transmission line. The forward (or incident) signal mixes with the reverse (or reflected) signal to cause a voltage standing wave pattern on the transmission line. The ratio of the maximum to minimum voltage is known as VSWR, or Voltage Standing Wave Ratio.

A VSWR of 1:1 means that there is no power being reflected back to the source. This is an ideal situation that rarely, if ever, is seen. In the real world, a VSWR of 1.2:1 (or simply 1.2) is considered excellent in most cases. At a VSWR of 2.0, approximately 10% of the power is reflected back to the source. Not only does a high VSWR mean that power is being wasted, the reflected power can cause problems such as heating cables or causing amplifiers to fold-back.
There are various ways of measuring and/or calculating VSWR.

Where Emax = maximum measured voltage
Emin = minimum measured voltage
Ei = incident wave amplitude, volts
Er = reflected wave amplitude, volts
Where Prev = reverse power
Pfwd = forward power

VSWR can also be represented in terms of reflection coefficient:

Where 'p' is the reflection coefficient.

Controlled Impedance

Controlled impedance/Controlled dielectric PCB is a specially accurate PCB Manufacturing techniques used for the Circuit Board Design. Which means by controlling the entire board traces with finite trce dimensions(width,Height,Dielectric Strength,Copper quality(1oz,2 oz) etc).So while during the manufacturing time,Controlled impedance can be achieved by measuring each trace impedance through out the running length by using TDR(Time Domain Reflectometry). Controlled impedance Board keeps all the copper trace routes with in a Accurate tolerance level. If you specify controlled impedance/controlled dielectric, they will test your board to ensure that the traces are at the specified impedance. In your fabrication notes on your PCB printout, specify the nets and their targeted impedance (with tolerance for the USB, e.g., 90 ohms +/-10 ohms or 50 ohms +/-5 ohms).When board traces carry high frequency signals(SDRAM,DDR,DDR2&3,PCI etc), care must be taken to design traces matching the impedance of the driver and receiver devices. The longer the trace or the higher the frequencies, the higher is the need to control the trace impedance.If the High Frequency trace impedance tolerance is higher that might cause serious signal integrity issue.

Track width reference table &Clearance for electrical conductors

Effects of Stray Capacitance..

Mutual capacitance CM between adjacent pins of a logic devices can couple voltages on to sensitive inputs.The figure shown depicts one such situation.

The cross talk introduced by pin 1 on pin 2 is given as

Crosstalk = ( Rpin2 x CM)/T10-90

Rpin2 is the impedance seen by pin 2. For the current situation it is 37.5ohms.

T10-90 is the rise time at pin 1, and is given as 5ns.

Therefore crosstalk factor is 0.03 or 3%.

From the equation it is clear that cross talk becomes more serious as rise time get shorter or with higher impedance input connection.

The below figure illustrates high-impedance input problem. Without C1 and C2 the impedance of the R1 and R2 is so high that we expect capacitive crosstalk to be a problem. Using the same equation we get a crosstalk factor of 8. This means practically all the clock signal from pin 1 will appear on pin 2.

The capacitors C1 and C2 are introduced to seal off this crosstalk problem.When dealing with capacitive loads on a receiveing circuit, the percentage of crosstalk is just equal to the ratio of the capacitance: Crosstalk = CM / CI

With CI set to 0.01uF, we get a crosstalk of only 0.0004.

Adjacent lead capacitance of logic packages are given below.

EtherCAT!!!

EtherCAT is a technology used for the controlled Automation by the use of existing Ethernet Backbone. EtherCAT (Ethernet Control Automation Technology) is a high-performance, industrial communication protocol for deterministic Ethernet.It can be used for the Automatic meter reading with in the microsecond range from greater than 5000 nodes. It extends the IEEE 802.3 Ethernet standard to transfer data with predictable timing and precise synchronization.EtherCAT implements a master/slave architecture over standard Ethernet cabling. EtherCAT masters from National Instruments consist of real-time controllers with dual Ethernet ports such as NI CompactRIO, PXI, and Industrial Controllers. Each NI slave also contains two ports that permit daisy chaining from the master controller.

Termination Tips for Dynamic RAMs

Series Termination- Recommended for SDRAM designs and DDR designs having fewer than four components, with trace lengths of ≤2in (5cm).

Parallel Termination- Recommended for DDR designs with trace lengths >2in (5cm).

Welcome to Hardware Routes !!!

Welcome to Hardware Routes....
The new Route to Hardware Development and enhancement..
The route to enhance our skills, ideas and contribute...

100BaseT/TX/Fx-Explored

Hi All,

We are all heard about 100Base-T,100Base-Tx/FX,100Base X signaling over the Ethernet .Just check out what it does actually meant for


100 Means-Data rate of the Ethernet signaling that is 100Mbps or 1000Mbps.
Base Refers to -Base Band Signaling schemes.Which means only Ethernet signals are carried on the medium.
T Refers to-Physical Medium That carries the signal that is Twisted Pair.
X Refers to-It is a Place holder for the Fx and Tx meidum.That is Fx-Fiber Pair for Fast Ethernet and TX-Twisted Pair for Fast ethernet
For examples;

100BASE-TX (100 Mbit/s over two-pair Cat5 or better cable)

100BASE-T4 (100 Mbit/s over four-pair Cat3 or better cable)

100BASE-T2 (100 Mbit/s over two-pair Cat3 or better cable)


Please provide feed back on this.Also please do continue update this forum for the technical upgradation....!!!!! ....