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).

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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....!!!!! ....