This document discusses various techniques for filtering and measuring high-speed logic signals, including:
(1) Common types of filters like low-pass, high-pass, band-pass and tuned filters that allow certain frequency ranges to pass.
(2) How filtering is done in the frequency domain rather than the time domain.
(3) Examples of low-pass and high-pass filters and how their cut-off frequencies determine what frequencies can pass.
(4) Issues that can impact accurate measurement of fast signals, such as limited bandwidth of oscilloscope probes and induced noise from ground loops or shield currents. Special techniques for minimizing these problems are also covered.
The USB 2.0 standard is widely deployed in both computer and embedded systems. Compliance testing for this standard includes signal integrity as well as a number of low-level protocol tests.
This presentation provides an overview of the test requirements for USB 2.0 compliance and provide background on each test case. Details of fixtures and signal integrity requirements are highlighted in detail.
For more information visit http://rohde-schwarz-scopes.com or call (888) 837-8772 to speak to a local Rohde & Schwarz expert.
Webinar Slides: Probing in Power Electronics - What to use and whyHilary Lustig
Join Teledyne LeCroy for this webinar as we provide an overview of the different HV rated probe specifications and topologies, explain what measurement each probe topology is ideally suited for, and provide real-word examples and comparisons between a variety of different probes and amplifiers.
(Slides from Live webinar on September 25, 2014, presented by Mike Schnecker. Watch the webinar On-Demand here: http://goo.gl/LkjUUg)
Attendees Will Learn:
An overview of switched mode power supplies
Common measurements (ie, what to measure and why)
Circuit loading and probing considerations
How instrument specifications impact measurement accuracy
Switched mode power supplies have become ubiquitous in electronics as they provide precise voltages including high power with very high efficiency. The efficiency of these power supplies requires low loss power transistors and the design requires measurement of highly dynamic voltages. Voltage levels can vary from millivolts to hundreds of volts in some applications.
In this webinar, the proper use of a digital oscilloscope to accurately measure these voltages will be discussed along with key aspects of instrument performance such as noise and overdrive recovery that affect the accuracy of the measurement.
The USB 2.0 standard is widely deployed in both computer and embedded systems. Compliance testing for this standard includes signal integrity as well as a number of low-level protocol tests.
This presentation provides an overview of the test requirements for USB 2.0 compliance and provide background on each test case. Details of fixtures and signal integrity requirements are highlighted in detail.
For more information visit http://rohde-schwarz-scopes.com or call (888) 837-8772 to speak to a local Rohde & Schwarz expert.
Webinar Slides: Probing in Power Electronics - What to use and whyHilary Lustig
Join Teledyne LeCroy for this webinar as we provide an overview of the different HV rated probe specifications and topologies, explain what measurement each probe topology is ideally suited for, and provide real-word examples and comparisons between a variety of different probes and amplifiers.
(Slides from Live webinar on September 25, 2014, presented by Mike Schnecker. Watch the webinar On-Demand here: http://goo.gl/LkjUUg)
Attendees Will Learn:
An overview of switched mode power supplies
Common measurements (ie, what to measure and why)
Circuit loading and probing considerations
How instrument specifications impact measurement accuracy
Switched mode power supplies have become ubiquitous in electronics as they provide precise voltages including high power with very high efficiency. The efficiency of these power supplies requires low loss power transistors and the design requires measurement of highly dynamic voltages. Voltage levels can vary from millivolts to hundreds of volts in some applications.
In this webinar, the proper use of a digital oscilloscope to accurately measure these voltages will be discussed along with key aspects of instrument performance such as noise and overdrive recovery that affect the accuracy of the measurement.
Instrumentation: Liquid and Gas Sensing (Design Conference 2013)Analog Devices, Inc.
This session focuses on liquid and gas sensing in instrumentation applications.
Liquid Sensing:
Visible light absorption spectroscopy and colorimetry are two fundamental tools used in chemical analysis. Most of these light-based systems use photodiodes as the light sensor, and require similar high input impedance signal chains. This session examines the different components of a photodiode amplifier signal chain, including a programmable gain transimpedance amplifier, a hardware lock-in amplifier, and a Σ-Δ ADC that can measure a sample and reference channel to greatly reduce any measurement error due to variations in intensity of the light source.
Gas Sensing:
Many industrial processes involve toxic compounds, and it is important to know when dangerous concentrations exist. Electrochemical sensors offer several advantages for instruments that detect or measure the concentration of toxic gases. This session will describe a portable toxic gas detector using an electrochemical sensor. The system presented here includes a potentiostat circuit to drive the sensor, as well as a transimpedance amplifier to take the very small output current from the sensor and translate it to a voltage that can take advantage of the full-scale input of an ADC.
Active filters are type of filters which use the operational amplifier ics for their operation and in this slides any one can get more information in little bit of time. so i recommended if any one want to study filters then must read it.
Webinar Slides: Probing Techniques and Tradeoffs – What to Use and Whyteledynelecroy
Engineers must commonly probe low and high frequency signals with high signal fidelity. Typical passive probes with high input impedance and capacitance provide good response at lower frequencies, but inappropriately load the circuit and distort signals at higher frequencies.
Join Teledyne LeCroy for this webinar as we discuss:
- Selecting the right probing techniques to maximize the accuracy of your measurements
- Probe specifications and their implications on the measured signal
- Variety of probes and accessories available for measurement
- Virtual probing software tools that allow the user to probe the signal when direct access is physically impossible
Webinar Slides: Probing in Power Electronics - What to use and whyteledynelecroy
Join Teledyne LeCroy for this webinar as we provide an overview of the different HV rated probe specifications and topologies, explain what measurement each probe topology is ideally suited for, and provide real-word examples and comparisons between a variety of different probes and amplifiers.
Instrumentation: Liquid and Gas Sensing (Design Conference 2013)Analog Devices, Inc.
This session focuses on liquid and gas sensing in instrumentation applications.
Liquid Sensing:
Visible light absorption spectroscopy and colorimetry are two fundamental tools used in chemical analysis. Most of these light-based systems use photodiodes as the light sensor, and require similar high input impedance signal chains. This session examines the different components of a photodiode amplifier signal chain, including a programmable gain transimpedance amplifier, a hardware lock-in amplifier, and a Σ-Δ ADC that can measure a sample and reference channel to greatly reduce any measurement error due to variations in intensity of the light source.
Gas Sensing:
Many industrial processes involve toxic compounds, and it is important to know when dangerous concentrations exist. Electrochemical sensors offer several advantages for instruments that detect or measure the concentration of toxic gases. This session will describe a portable toxic gas detector using an electrochemical sensor. The system presented here includes a potentiostat circuit to drive the sensor, as well as a transimpedance amplifier to take the very small output current from the sensor and translate it to a voltage that can take advantage of the full-scale input of an ADC.
Active filters are type of filters which use the operational amplifier ics for their operation and in this slides any one can get more information in little bit of time. so i recommended if any one want to study filters then must read it.
Webinar Slides: Probing Techniques and Tradeoffs – What to Use and Whyteledynelecroy
Engineers must commonly probe low and high frequency signals with high signal fidelity. Typical passive probes with high input impedance and capacitance provide good response at lower frequencies, but inappropriately load the circuit and distort signals at higher frequencies.
Join Teledyne LeCroy for this webinar as we discuss:
- Selecting the right probing techniques to maximize the accuracy of your measurements
- Probe specifications and their implications on the measured signal
- Variety of probes and accessories available for measurement
- Virtual probing software tools that allow the user to probe the signal when direct access is physically impossible
Webinar Slides: Probing in Power Electronics - What to use and whyteledynelecroy
Join Teledyne LeCroy for this webinar as we provide an overview of the different HV rated probe specifications and topologies, explain what measurement each probe topology is ideally suited for, and provide real-word examples and comparisons between a variety of different probes and amplifiers.
Access the video from this presentation for free from
http://www.rohde-schwarz-usa.com/DebuggingEMISS_On-Demand.html
Overview:
Electromagnetic interference is increasingly becoming a problem in complex systems that must interoperate in both digital and RF domains. When failures due to EMI occur it is often difficult to track down the sources of such failures using standard test receivers and spectrum analyzers. The unique ability of real-time spectrum analysis and synchronous time domain signal acquisition to capture transient events can quickly reveals details about the sources of EMI.
What You Will Learn:
How to isolate and analyze sources of EMI using an oscilloscope
Measurement considerations for correlating time and frequency domains
Near field probing basics
Presented By:
Dave Rishavy, Product Manager Oscilloscopes, Rohde & Schwarz
Dave Rishavy has a BS in Electrical Engineering from Florida State University and an MBA from the University of Colorado. Prior to joining Rohde and Schwarz, Mr. Rishavy gained over 15 years of experience in the test and measurement field at Agilent Technologies. This included positions in a wide range of technical marketing areas such as application engineering, product marketing, marketing management and strategic product planning. While at Agilent, Dave led the marketing and industry segment teams for the Infiniium line of oscilloscopes as well as high end logic analysis.
Webinar Slides: Measurements and Analysis for Switched-mode Power Designsteledynelecroy
This webinar covers the measurements of interest for designers of switched-mode power conversion circuits and devices. With the goal of high efficient and reliable designs, we review the acquisition of voltage and current, their relationship in switched-mode power conversion circuits.
We review specific power circuit performance areas including the analysis of power device switching losses, conduction losses, dynamic on-resistance, control loop response, power quality, conducted emissions, best practices for probing power circuits, and power rail integrity measurements.
what is Band pass filter (low and high pass) application, working and output voltages values on CRO with different frequencies as well as Picture of PSpice software (output).
BJT and MOS, Advanced Circuit Topologies, concept of tracking, mm-Wave frequency beyond 30GHz, Bandgap is a stable, well defined, and constant current source
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2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
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1. High-speed logic: Measurement (v.9a) 1
CENG3480_B2
Measurement Techniques
Reference: Chapter 3 Measurement Techniques of
High speed digital design , by Johnson and Graham
2. High-speed logic: Measurement (v.9a)2
Revision: frequency domain processing
and filtering
(1) Low-pass filter
(2) High-pass filter
(3) Band pass filter
(4) Tuned filter (narrow band pass filter)
See http://www.ee.duke.edu/~cec/final/node1.html
3. High-speed logic: Measurement (v.9a)3
Revision: Filtering is in Frequency domain not
time domain
Filtering is in Frequency domain, don’t mix up with high/low
amplitude levels
Higher amplitude
lower freq.
Lower amplitude
Higher freq.
timeamplitude
6. High-speed logic: Measurement (v.9a)6
A common example of a low pass filter: An operational
amplifier:
Diagram of gain bandwidth product, from [1]
7. High-speed logic: Measurement (v.9a)7
(1) Low pass filter (Frequency low than F-3dB can pass, or has
power gain more than 0.5)
(1) Low pass (e.g. op.amp)
At low freq, Gain=1=0dB
At -3dB cut off, gain = 0.5, = -3dB
analog
system
Vin Vout
Frequency
Gain in dB = 20 log10(Vout/Vin)
0
-3dB
Flowpass(-3dB) =1/2πRC
3dB cut off point
B=Bandwidth
VcR C
Ic(t)
E.g.
8. High-speed logic: Measurement (v.9a)8
(2) High pass filtering, (Frequency higher than F-3dB can pass, or
has power gain more than 0.5)
High pass
At low freq, Gain=0= -∞dB
At -3dB cut off, gain =0.5, = -3dB
0
F-highpass(-3dB) = 1/2π(L/R)
3dB cut off point
R L analog
system
Vin Vout
Frequency
Gain in dB = 20 log10(Vout/Vin)
-3dB
9. High-speed logic: Measurement (v.9a)9
(3) Band - Pass Filters (Frequency within a range can pass)
0dB 3dB
gain
Band width
E.g. A band-pass filter by combining a
low pass F low-pass(-3dB) filter ,
an ideal amplifier and
a high pass F high-pass(-3dB) filter.
Ideal amplifier
R L
10. High-speed logic: Measurement (v.9a)10
(4) Tuned filter: special case of a band-pass filter -- only a
narrow band can pass
When the low pass F low-pass(-3dB), and the a high pass F high-
pass(-3dB)filter are close.
Fc=center frequency,
∆F=bandwidth (narrow)
0dB
3dB
gain
Band width ∆F
Fc =1/[2π(LC) 1/2
]
Frequency
R
LC
11. High-speed logic: Measurement (v.9a)11
Rise time and bandwidth of CRO probes
All scientific instruments have limitations
Limitations of oscilloscope systems
inadequate sensitivity
• Usually no problem because except most sensitive digital network, we are
well above the minimum sensitivity (analogue system is more sensitive)
insufficient range of input voltage?
• No problem. Usually within range
limited bandwidth?
• some problems because all veridical amplifier and probe have a limited
bandwidth
Two probes having different bandwidth will show different
response. Using faster probe
Using slower probe (6 MHz)
12. High-speed logic: Measurement (v.9a)12
Oscilloscope probes
Components of oscilloscope systems
Input signal
Probe
Vertical amplifier
We assume a razor thin rising edge. Both probe and vertical
amplifier degrade the rise time of the input signals.
13. High-speed logic: Measurement (v.9a)13
Combined effects: approximation
Serial delay
The frequency response of a probe, being a combination of several random
filter poles near each other in frequency, is Gaussian.
2
1
22
2
2
1_ )( Ncompositerise TTTT +⋅⋅⋅++=
Rise time is 10-90% rise time
When figuring a composite rise time, the squares of 10-90% rise times add
Manufacturer usually quotes 3-db bandwidth F3db
approximations T10-90= 0.338/F3dBfor each stage (obtained by simulation)
14. High-speed logic: Measurement (v.9a)14
Example:
Given: Bandwidth of probe and scope = 300 MHz
Tr signal = 2.0ns
Tr scope = 0.338/300 MHz = 1.1 ns
Tr probe = 0.338/300 MHz = 1.1 ns
Tdisplayed = (1.12
+ 1.12
+2.02
)1/2
= 2.5 ns
For the same system, if Tdisplayed = 2.2 ns, what is the actual rise time?
Tactual = (2.22
- 1.12
– 1.12
)1/2
= 1.6 ns
15. High-speed logic: Measurement (v.9a)15
Self-inductance of a probe ground loop
A Primary factor degrading the performance
Current into the probe must traverse the ground loop on the way back to source
The equivalent circuit of the probe is a RC circuit
The self-inductance of the ground loop, represented on our schematic by series
inductance L1, impedes these current.
16. High-speed logic: Measurement (v.9a)16
Typically, 3 inches (of 0.02” Gauge wire loop) wire on
ground plane equals to (approx) 200 nH
Input C = 10pf
TLC = (LC)1/2
= 1.4ns
T10-90 = 3.4 TLC = 4.8ns
This will slow down the response a lot.
17. High-speed logic: Measurement (v.9a)17
Estimation of circuit Q
Output resistance of source combine with the loop inductance & input
capacitance is a ringing circuit.
Where
Q is the ratio of energy stored in the loop to energy lost per radian during
resonant decay.
Fast digital signals will exhibit overshoots. We need the right Rs to damp
the circuit. On the other hand, it slows down the response.
sR
CL
Q
2/1
)/(
≈
18. High-speed logic: Measurement (v.9a)18
Impact: probe having ground wires, when using to view very fast signals
from low-impedance source, will display artificial ringing and overshoot.
A 3” ground wire used with a 10 pf probe induces a 2.8 ns 10-90% rise
time. In addition, the response will ring when driven from a low-
impedance source.
19. High-speed logic: Measurement (v.9a)19
Remedy
Try to minimize the earth loop wire
Grounding the probe close to the signal source
Back to page 29
20. High-speed logic: Measurement (v.9a)20
Spurious signal pickup from probe ground loops
3
21
08.5
r
AA
LM =
mVsVnh
dt
dI
LV Mnoise 12)/100.7)(17.0( 7
=×==
Mutual inductance between Signal
loop A and Loop B
where
A1 (A2) = areas of loops
r = separation of loops
Refer to figure for values.
In this example, LM = 0.17nH
Typically IC outputs
max dl/dt = 7.0 * 107
A/s
12mV is not a lot until you have a 32-bit bus; must try to minimize loop area
22. High-speed logic: Measurement (v.9a)22
How probes load down a circuit
Common experience
Circuit works when probe is inserted. It fails when probe is removed.
Effect is due to loading effect, impendence of the circuit has
changed. The frequency response of the circuit will change as
a result.
To minimize the effect, the probe should have no more than
10% effect on the circuit under test.
E.g. the probe impedance must be 10 times higher than the source
impedance of the circuit under test.
23. High-speed logic: Measurement (v.9a)23
An experiment showing the probe loading effect
A 10 pf probe looks like 100 ohms to a 3 ns rising edge
Less probe capacitance means less circuit loading and better measurements.
A 10 pf probe loading a 25 ohm circuit
24. High-speed logic: Measurement (v.9a)24
Special probing fixtures
Typical probes with 10 pf inputs and one 3” to 6” ground
wire are not good enough for anything with faster than 2ns
rising edges
Three possible techniques to attack this problem
Shop built 21:1 probe
Fixtures for a low-inductance ground loop
Embedded Fixtures for probing
25. High-speed logic: Measurement (v.9a)25
Shop-built 21:1 probe
Make from ordinary 50 ohm coaxial cable
Soldered to both the signal (source) and local ground
Terminates at the scope into a 50-ohm BNC connector
Total impedance = 1K + 50 ohms;
if the scope is set to 50 mv/divison,
the measured value is = 50 * (1050/50) = 1.05 V/division
26. High-speed logic: Measurement (v.9a)26
Advantages of the 21:1 probe
High input impedance = 1050 ohm
Shunt capacitance of a 0.25 W 1K resistor is around 0.5 pf,
that is small enough.
But when the frequency is really high, this shunt capacitance may
create extra loading to the signal source.
Very fast rise time, the signal source is equivalent to
connecting to a 1K load, the L/R rise time degradation is
much smaller than connecting the signal to a standard 10 pf
probe.
27. High-speed logic: Measurement (v.9a)27
Fixtures for a low-inductance ground loop
Refer to figure on page 19
Tektronix manufactures a probe fixture specially designed to
connect a probe tip to a circuit under test.
28. High-speed logic: Measurement (v.9a)28
Embedded Fixture for Probing
Removable probes disturb a
circuit under test. Why not
having a permanent probe
fixture?
The example is a very
similar to the 21:1 probe. It
has a very low parasitic
capacitance of the order 1
pf, much better than the 10
pf probe.
Use the jumper to select
external probe or internal
terminator.
29. High-speed logic: Measurement (v.9a)29
Avoiding pickup from probe shield currents
Shield is also part of a current path.
Voltage difference exists between logic ground and scope
chassis; current will flow.
This “shield current * shield resistance R shield“ will produce noise
Vshield
30. High-speed logic: Measurement (v.9a)30
VShield is proportional to shield resistance, not to shield
inductance because the shield and the centre conductor are
magnetically coupled. Inductive voltage appear on both
signal and shield wires.
To observe VShield
Connect your scope tip and ground together
Move the probe near a working circuit without touching anything. At
this point you see only the magnetic pickup from your probe sense
loop
Cover the end of the probe with Al foil, shorting the tip directly to the
probe’s metallic ground shield. This reduces the magnetic pickup to
near zero.
Now touch the shorted probe to the logic ground. You should see
only the VShield
31. High-speed logic: Measurement (v.9a)31
Solving VShield problem
Lower shield resistance (not possible with standard probes)
Add a shunt impedance between the scope and logic ground.
Not always possible because of difficulties in finding a good
grounding point
Turn off unused part during observation to reduce voltage
difference
Not easy
Use a big inductance (magnetic core) in series with the shield
Good for high frequency noise.
But your inductor may deteriorate at very high frequency.
Redesign board to reduced radiated field.
Use more layers
Disconnect the scope safety ground
Not safe
32. High-speed logic: Measurement (v.9a)32
Use a 1:1 probe to avoid the 10 time magnification when
using 10X probe
Use a differential probe arrangement
33. High-speed logic: Measurement (v.9a)33
Viewing a serial data transmission system
Jitter observed due to intersymbol interference and additive
noise.
To study signal, probe point D and use this as trigger as well.
34. High-speed logic: Measurement (v.9a)34
No jitter at trigger point due to repeated syn with positive-
going edge.
This could be misleading
For proper measurement, trigger with the source clock
The jitter is around half of the previous one.
If source clock is not available, trigger on the source data signal point
A or B (where is minimal jitter)
35. High-speed logic: Measurement (v.9a)35
Slowing Down the System clock
Not easy to observe high speed digital signals which include
ringing, crosstalk and other noises.
Trigger on a slower clock (divide the system clock) allows
better observations because it allows all signals to decay
before starting the next cycle.
It will help debugging timing problems.
36. High-speed logic: Measurement (v.9a)36
Observing crosstalk
Crosstalk will
Reduce logic margins due to ringing
Affect marginal compliance with setup and hold requirements
Reduce the number of lines that can be packed together
Use a 21:1 probe to check crosstalk
Connect probe and turn off machine; measure and make sure there is
minimal environment noise.
Select external trigger using the suspected noise source
Then turn on machine to observe the signal which is a combination of
primary signal, ringing due to primary signal, crosstalk and the noise
present in our measurement system
38. High-speed logic: Measurement (v.9a)38
Try one of the followings to observe the cross talk
Turn off primary signal (or short the bus drivers)
• Varying the possible noise source signal (e.g. signal patterns for the bus)
Compare signals when noise source is on and off
• Talk photos with the suspected noise source ON and source OFF.
• The difference is the crosstalk
Generating artificial crosstalk
• Turn off, disabled, short the driving end of the primary signal. Induce a
step edge of know rise time on the interfering trace and measure the
induced voltage.
• Useful technique when measuring empty board without components.
39. High-speed logic: Measurement (v.9a)39
Measuring Operating Margins
In digital system measurements, we are interested to stress the system to
ensure the system is within operation margin specified.
Make sure the arrangement is automatic and self recovery
Some of the common tests
Additive noise
• Add random noise to every node
• Sine waves, square waves or random pattern
• Difficult to administer
• Suitable for data receivers and transmitters
Adjusting the timing of a large bus (clock skew margin test)
• Test the combine effects of system setup time, hold time and operating margin etc.
• Connect the devices’ clock signals using the following methods.
– Clock adjustment by coax delay (vary the length)
– Clock adjustment by pulse generator (variable delays)
– Simple circuits for clock phase adjustment
– Clock adjustment by a phase-locked loop
– Clock adjustment by voltage variation
40. High-speed logic: Measurement (v.9a)40
Power Supply
• Power supply variation can change response characteristics
• Vary the supply over a + 10% range
Temperature
• Temperature will vary the delay characteristics
• Can use cooling spray, blow dryer etc. Some companies use temperature
control ovens
• Make sure the temperature probe is attached to the right place
Data Throughput
• Compose a suite of operations that exercise each individual connections
• Not easy to compose test pattern that represents the real situations. Often
system passes tests but fails at real operations.
• Good data pattern will uncover unexpected avenues of noise coupling
which causes failures
• Complex tests are expensive