This presentation is designed as per Unit V - Electronic Product Design (Elective II)-SPPU Syllabus. This Study material is useful for BE E & TC students.
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Unit V - Product Debugging and Testing
1. Dr. Anagha Parag Khedkar
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2. Contents
Steps of Debugging, Techniques for troubleshooting,
characterization
Electromechanical components, passive components,
active components
active devices, operational amplifier, Analog-Digital
Conversion
Digital Components, Inspection and test of
components
Simulation, Prototyping and testing.
Integration, validation and verification. EMI & EMC
issues.
Electronic Product Design Unit V as per BE E & TC
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3. Debugging, Testing, Troubleshooting
These tasks are performed at different times during
product's lifetime.
debugging-done during early phases, testing-done
before delivery of product, troubleshooting-done
afterwards
debugging- used to identify the cause of problems
occured in design & implementation.
testing- it assumes that design is correct, identifies
problems occured during manufacturing.
troubleshooting- design is correct & product worked at
one time. It identifies which hardware components have
failed.
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 3
4. Introduction to Debugging &
Testing
Debugging: tracking & finding faults & correcting
undesirable system behavior
Debugging is used to focus search for solution
Testing: It involves variety of operations that verify
operation within specified environment.
Hardware Testing: involves inspection, analysis of
destructive & nondestructive parts, static & dynamic
evaluation
For reliability, planning for testing early is imp.
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SPPU syllabus by Dr. Anagha P. Khedkar 4
5. 5 Steps to debugging
Observe & characterize
Brainstorm
Hypothesize
Test
Repeat steps 1 thr 4 until problem is solved.
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 5
6. 5 Steps to debugging
Start by collecting observations & characterizing the
problem.
Brainstorm all possible causes for problems & list them
Build hypothesis (A hypothesis is a testable statement
about the relationship between two or more variables or a
proposed explanation for some observed phenomenon. )
Design experiments that test hypothesis
Repeat steps till working hypothesis is found.
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 6
7. Checklist for debugging
1. Visually inspect ckt.for
missing components, broken wires, traces, bent pins,
leads, damage etc.
2. Check continuity
3. Check power connections
4. Check equipment status
5. Verify schematic
6. Verify software
7. Take a break
8. Get another perspective
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8. Troubleshooting
Troubleshooting is the process of identifying and
fixing problems.
Computer troubleshooting may
involve hardware or software and can sometimes
involve both at the same time.
The basic process of troubleshooting is to check the
most general possible problems first, and then
gradually check for more specific problems.
This provides a logical approach to problem solving
and can apply to multiple types of products.
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 8
9. Techniques for troubleshooting
To collect necessary observations, we need proper
diagnostic equipments like power supply, DMM, function
generator, logic analyzer, ICE, CRO, supply of components,
soldering iron.
CRO-High bandwidth, DMM- high accuracy, CRO probe
i/p capacitance – loading, soldering iron heating aspects,
good stock of precision components
CRO probes can introduce disturbances in CUT thr load
capacitances, ground lead problems, cables
CRO probe is an integral part of ckt under test. Its i/p
resistance & capacitance load a ckt & can affect operation
of CUT
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 9
10. ICE: In Circuit Emulator
A circuit for emulating target system remains
independent of a particular targeted system and
processor
Emulator or ICE provides great flexibility
and ease for developing various
applications on a single system in place of
testing that multiple targeted systems.
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 10
11. ICE
Interface COM port of a computer
Emulates target MCU IOs
ICE socket connects MCU externally Interface COM
port of a computer
Uses computer developed object files and hex files for
the MCU
Uses debugger at the computer developed files for the
MCU application
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 11
12. Techniques for troubleshooting
Adjust the probe compensation
This is done by turning screw that adjusts variable
capacitor.
Build FET buffer into probe to provide very high input
impedance.
Ground lead on probe (becomes inductive)can cause
problems of signal ringing at high frequencies. To avoid
this, keep ground leads as short as possible.
Cabling can significantly alter signals in probed ckts.
Capacitance loading, inductive loops & improper
termination will degrade rise time of signal pulses.
Electronic Product Design Unit V as per BE E & TC
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14. FET buffer into probe
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15. Techniques for troubleshooting
1. General tips for power
2. Tips for analog ckts
3. Tips for digital ckts
4. Tips for S/w
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16. General tips for power
Electronic Product Design Unit V as per BE E & TC
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17. Tips for analog ckts
Keep leads short
Use right oscilloscope
Layout ckt & grounds properly
Choose proper location of resistors to reduce noise
from stray capacitances
Compensate the oscilloscope probe
Use FET i/p probe for high impedance ckts
Avoid long settling times
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SPPU syllabus by Dr. Anagha P. Khedkar 17
18. Tips for digital ckts
Use proper triggers to catch glitches on CRO & logic
analyzer
s/w in target system can aid debugging h/w
Use built in tests to test h/w. Built in tests to check
memory chips.
Use simple looping routines to check I/O ports.
Partition ckts – s/w & h/w modules. It isolates
problems & makes debugging easy.
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SPPU syllabus by Dr. Anagha P. Khedkar 18
19. Tips for S/w
Use modular designs
Do good documentation
Use proper tools
Some h/w tools also can help like LED, ICE, CRO
LED can glow to indicate whether program is toggling
a signal or not. E.g Serial communication programs
send data on TxD & receive on RxD. LEDs on TxD &
RxD to check data/pulses
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20. Characterization
First step in debugging is to characterize components
Test components and ckts in a variety of environments to
evaluate their performance & their margins
Do simulation of components to understand
characteristics of components. But testing of components
is necessary
Tests of components characterize parameter tolerances &
variations & provide for calibration of their functions. Tests
in different thermal environment.
E.g. power consumption of Ics, conversion accuracy of ADC
vary with temp., also other parameters.
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21. Electromechanical components
These include connectors, Fuses, switches, keyboards.
Connectors- metal contacts- consider its electrical,
mechanical, chemical properties
Resistance of contacts & current carrying capacity
change with wear, dust & force
Rate of corrosion in contacts
Specify this in the design & perform environmental
testing to verify reliability
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 21
22. Electromechanical components
Fuse- metallic conductor with specifies cross section &
resistance that melts when current density exceeds limit
Types of fuses- for various situations-normal blow/class F,
slow blow/type T
Consider fuse opening time duration, rated current
capacity
For use in international products, understand differences
in fuse, protection methods, current capacity & size
Fuse standards specify length & diameter in mm
Tests for fuses: measure statistical variation in time to open
ckt for high currents of 10 times rating, next 2 times rating,
test that terminals of blown fuse sustain high voltage
without arcing.
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 22
23. Electromechanical components
Switches: ergonomics, basics, parameters.
Switch properties- low contact resistance, low force to
maintain contact, no corrosion, durability, low cost,
durability.
Contacts-NO/NC
Current capacity rating-AC/DC application
Arcing across contacts
Contact bouncing
Precious metal contacts-cost
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24. Passive components
R,L, C- each has its characteristic properties, based on
manufacturing processes & materials used for each type of
component.
Use of resistors in ckt-current limiting, pull up, pull down,
impedance matching, voltage division, bias set, gain
control etc.
Resistance varies- manufacturing tolerances, temp.,
humidity, voltage stresses.
Tolerances:20%, 10%, 5%, 1%
At high frequencies, lead inductance & internal
capacitance –significant- changing impedance
Resistance contribute thermal noise
If resistors to be used at high temp., you will have to derate
amount of power that they dissipate.
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 24
25. Passive components- resistors
Types-carbon composition, carbon film, metal film,
thick film, thin film, wire wound, thin film
Characteristics: max. resistance, max. voltage, temp.
coefficient of resistance, accuracy, shelf life, stability
Wire wound- high precision, high power ratings(upto
2KW), excellent TCR(as low as 1 ppm/degree c)
Thin film-best TCR <1
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SPPU syllabus by Dr. Anagha P. Khedkar 25
26. Passive components-capacitors
Capacitor- function-to store charge
Types:block dc, pass ac, filter, couple, tune,
decouple/bypass, compensate, isolate, suppress noise
Capacitor’s impedance varies with frequency.
Capacitor- leakage resistance, lead inductance, lead
resistance
Use high Q capacitor with low ESR, ESL
Capacitor: breakdown voltage, memory effect-dielectric
absorption(reduce discharge capabilities)
Capacitor-failures: open ckt, short ckt, leakage failure,
arcing between plates may occur
Causes: excessive voltage, current, temp. , sudden charging
& dischargingElectronic Product Design Unit V as per BE E & TC
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27. Passive components: inductor
Role of inductor- significant in power supplies & high
voltage generators
Inductance – depends on no. of turns, current,
permeability
Nonlinear devices with hysteresis, saturation, eddy
current.
Most of time-inductors- custom produced for
application.
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 27
28. Active Devices
These either amplify or control greater power with lesser
power.
Mechanical relay, solid state relay, semiconductors- diode,
transistors, optoisolators
Relay: nonlinear switched device
Power required to pull in armature is greater than power
required to hold armature closed.
So switching relay with larger current & holding it with
lower current, power dissipation in relay can be reduced.
Max power dissipation is limited by overheating within coil.
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 28
29. Active devices: mechanical relay
Characterize relay coils by their resistance &
inductance.
Resistance sets I2R dissipation, inductance determines
spike suppression
Operational life of relay can be specified by no. of
open/closed cycles of armature & contacts can
complete without failure.
Test & specify relay for shock & vibration.
High voltage test for relay
Wear & tear of relay contacts
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 29
30. Active devices: semiconductors
Test & qualify each component
Maintain alternative source for each component
Common problems with devices- leakage current,
reverse current, safe operating areas, thermal effects,
ESD & parameter variations.
Do not exceed voltage, temp. & current ratings
Curve tracer helps to identify good or bad
components.
Transistors-gain vary, switching speed , current gain &
frequency response
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31. Active devices:MOSFET
MOSFET: high impedance, low noise, no thermal
runaway
Consider parameters: Id Vs Vds, noise, gate
capacitance
Allow margins of tolerance on parameters while
designing in ckt
Failures: defects in silicon die, thermal & current stress
betn wire bond & die
Electrical & temp. testing – reveals defects in die
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SPPU syllabus by Dr. Anagha P. Khedkar 31
32. Op-amps
Op-amps-amplifiers, filters, oscillators, control
systems
Passive components around opamp cause most
problems
Don’t rely on characteristics not guaranteed by
manufacturer.
Virtual ground at i/p - at high frequencies, these
inputs have significant error voltage to drive output
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SPPU syllabus by Dr. Anagha P. Khedkar 32
33. Op-amp characteristics
Test ckts for imp. Parameters of opamp
Offset voltage
Loop gain
CMRR
Slew rate
o/p noise
PSRR
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34. Test ckts for imp. Parameters of
opamp
Electronic Product Design Unit V as per BE E & TC
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35. Test ckts for imp. Parameters of op-
amp
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36. Test ckts for imp. Parameters of op-
amp
Electronic Product Design Unit V as per BE E & TC
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37. Test ckts for imp. Parameters of op-
amp
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38. ADC
No single test can completely characterize ADC/DAC
Tests are specific as per application
Some apps need ADC’s good transient response, some
need linearity, high resolution
Verify performance & accuracy of converters at desired
conversion speed.
Converters are subjected to errors from sources viz.
architecture, quantization, fabrication & ckt layout
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SPPU syllabus by Dr. Anagha P. Khedkar 38
39. ADC: equipment to evaluate
converters
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40. ADC: equipment to evaluate
converters
It should have proper amplifier bandwidth, settling
time, filtering to remove harmonics & broadband
noise, low jitter clock, clean power supply with
decoupling & controlled temp.
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SPPU syllabus by Dr. Anagha P. Khedkar 40
41. ADC: Basic definitions
Ideal transfer function for ADC: graph of binary code
Vs Analog input
In transfer function, single binary value represents a
range of analog values in quantization band around its
code center point.
Analog values not exactly at the center have associated
amount of quantization error
Resolution of ADC defines its capability to represent
analog values. The no. of bits in o/p sets resolution
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 41
42. ADC: Errors
Quantization error: range of analog values around the code
center point.
Differential nonlinearity: Differences in quantization band
between each digital code. It can vary between -1 LSB & >
+1LSB .
Integral nonlinearity: deviation from linear transfer
function
Missing codes
Aperture jitter
I/p noise
Settling error(DAC): time for o/p to reach final analog
output value
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SPPU syllabus by Dr. Anagha P. Khedkar 42
43. ADC 0808 specifications
Easy interface to all microprocessors
Operates ratiometrically or with 5 V DC or analog span
adjusted voltage reference
No zero or full-scale adjust required
8-channel multiplexer with address logic
0V to 5V input range with single 5V power supply
Outputs meet TTL voltage level specifications
Resolution 8 Bits
Non-linearity +/-1/2LSB
Single Supply 5 V DC
Low Power 15 mW
Conversion Time 100 µs
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44. DAC
Resolution in no. of bits
Settling time: It is one of the important dynamic parameter. It
represents the time it takes for the output to settle within a specified
band ± (1/2) LSB of its final value
Accuracy
Quantization error
Linearity
Monotonicity: A Digital to Analog converter is said to be monotonic if
the analog output increases for an increase in the digital input.
Conversion Time:
It is the time taken for the D/A converter to produce the analog output
for the given binary input signal. It depends on the response time of
switches and the output of the Amplifier.
Stability:
The ability of a DAC to produce a stable output all the time is called as
Stability.
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SPPU syllabus by Dr. Anagha P. Khedkar 44
45. DAC
DAC availability: current o/p or voltage o/p
Test for linearity: Compare o/ps from production DAC
with o/p of a precise converter as a reference(higher
resolution).
While testing for settling time, avoid overdriving the
differencing ckt.
Glitches occur during transitions of the digital input
signals
So choose either low-glitch DAC or deglitched DAC
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SPPU syllabus by Dr. Anagha P. Khedkar 45
46. Digital Components
These deal with more than high & low logic levels.
Digital components face 4 problems particularly at high
frequencies- ground bounce, phase jitter, metastability,
transmission line concerns
Ground bounce: also called simulteneous switching noise
can cause unswitched o/ps to exceed threshold of driven
gate forcing unwanted logic transition.
Factors contributing to ground bounce are signal rise time,
load capacitance, no. of simultaneous switched o/ps.
Avoid ground bounce by using good layout that reduces
inductive loop
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SPPU syllabus by Dr. Anagha P. Khedkar 46
47. Important Questions
Explain tecniques for Troubleshooting.
Define Debugging process and explain steps of
debugging.
Differentiate between active and passive components.
Explain Analog-Digital in detail.
What are the different steps in debugging? Differentiate
troubleshooting from debugging.
Compare different types of ADCs with respect to
resolution, power consumption, multiple inputs and
nonlinearity.
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SPPU syllabus by Dr. Anagha P. Khedkar 47
48. Watch Electronic Product Design Video Lectures
on My You Tube channel
Please Like, Subscribe & Share my You tube channel
:https://www.youtube.com/channel/UCGoQM5nMnSFYZb2akw4p
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Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 48
49. Text Book Reference
Kim Fowler, Electronic Instrument Design Oxford
university press.
Electronic Product Design Unit V as per BE E & TC
SPPU syllabus by Dr. Anagha P. Khedkar 49