Feb 022015

Tire size calculator

The results of this calculator are based on the mathematical equations of the sizes
entered, not the actual tire specs provided by the tire manufacturers. Please refer to the guides
supplied by manufacturers for exact specifications.Results within +3% of stock are considered acceptable.


Please enter actual Tread width – Aspect Ratio and Wheel / Rim diameter
(e.g. 205/65-R16)

Original Alternate
 /  –   /  – 

Graph: Actual speed vs. speedometer reading (km/h)

More about tires

Tire sizes are expressed by the manufacturers with three sets of numbers:

Tread width – Aspect Ratio – Wheel diameter (e.g. 215 55 R16)
Automobile tires are described by an alphanumeric tire code (in American English)
or tyre code (in British English, Australian English and others), which is
generally molded into the sidewall of the tire. This code specifies the
dimensions of the tire, and some of its key limitations,
such as load-bearing ability, and maximum speed.
Sometimes the inner sidewall contains information not
included on the outer sidewall, and vice versa.
For more in dept information about tire size and tyre codes see Wikipedia


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Jan 312015

infoSuper capacitor discharge time calculator.
This calculator determines timekeeping operation using a super capacitor (ultracap) based upon starting and ending capacitor voltages, discharge current, and capacitor size.

Formulas used:
Bt(seconds) = [C(Vcapmax – Vcapmin)/Imax]  This formula is valid for constant current only.
Bt(seconds) = -log(Vcapmin/Vcapmax)(RC) = t  This formula is valid for linear current only (simple resistive load).

  • Imax is the discharge current in amperes (A)
  • Vcapmin is the ending voltage in volts (V)
  • Vcapmax is the initial voltage in volts (V)
  • R is the equivalent resistive load in ohms(Ω) based on : R=Vcapmax/Imax
  • C is the capacitor value in farads 1F=1000 000μF=1000 000 000nF=1000 000 000 000pF
  • t is the time in seconds(s)

Edit the input fields and then click [Calculate]    
Vcapmax: V  
Vcapmin: V  
Capacitor Value: Farads  
Capacitor ESR: Ohms  
Imax uA  
R (calculated) Ohms  
Linear current discharge time: (simple resistor load) seconds  
Constant current discharge time: seconds  




More about this calculation

  • Vcapmax is the VCC maximum value that the capacitor is charged to.
  • Vcapmin is the minimum operating voltage you can tolerate before your circuit or component, which is backed up by the capacitor, stops working.
  • Imax is the maximum current that your circuit will discharge the capacitor.
    This can be a constant current or the initial linear current at Vcapmax.The Imax and Vcap values are used to calculate the equivalent resistance of the circuit, which is used in the
    equation to calculate the backup time.

RC Capacitor discgarge circuit
Figure 1.

From basic electronics, the formula to determine the voltage across a capacitor at any given time (for the
discharge circuit in Figure 1) is: V(t) = E(e-t/RC)

Rearranging this formula for time gives us: t = – log(V/E)(RC)
V is the ending voltage in volts (V)
E is the initial voltage in volts (V)
R is the resistive load in ohms(Ω)
C is the capacitor value in farads 1F=1000 000μF=1000 000 000nF=1000 000 000 000pF
t is the time in seconds


More about super capacitors
A supercapacitor, supercondenser, pseudocapacitor, electrochemical double layer capacitor (EDLC), or ultracapacitor,
is an electrochemical capacitor with relatively high energy density, typically on the order of thousands
of times greater than an electrolytic capacitor. For instance, a typical D-cell sized electrolytic capacitor
may have capacitance in the range of tens of millifarads. The same size electric double-layer capacitor
might reach several farads, an improvement of two orders of magnitude. Supercapacitors usually
yield a lower working voltage in the range 2,5 – 20V.
As of 2010 larger double-layer capacitors have capacities
up to 5,000 farads.[1] Also in 2010, the highest available supercapacitor energy density
is 30 Wh/kg,[2] lower than rapid-charging lithium-titanate batteries.

EDLCs have a variety of commercial applications, notably in “energy smoothing” and momentary-load devices.
They have applications as energy-storage devices used in vehicles, and for smaller applications like
home solar energy systems where extremely fast charging is a valuable feature.

Super capacitors are widely used as a backup power source for realtime clock circuits and memory in microcontroller applications for years.
More information in Wikipedia here.

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Apr 202012

infoFormula used in this
calculation is from the famous Wheelers approximations
which is accurate to <1% if the cross section is near
square shaped.

L (uH) =31.6*N^2* r1^2 / 6*r1+ 9*L + 10*(r2-r1)


  • L(uH)= Inductance in microHenries
  • N = Total Number of turns
  • r1 = Radius of the inside of the coil in meters
  • r2 = Radius of the outside of the coil in meters
  • L = Length of the coil in meters
Multilayer air cor inductors

NOTEThis formula applies at ‘low’ frequencies (<3MHz) using
enameled copper wire tightly wound.

Multilayer air coils Please note that the diameter is measured from center of wire trough
center of the coil and to center of the wire on the opposite side.

Inductance (L):
Coil Inner Diameter (d=2*r1):
Coil Length (l):
Wire Gauge: AWG
Number of Turns (N): turns
Turns per Layer: turns/layer
Number of Layers: layers
Coil Outer Diameter (D):
Wire Diameter:
Wire Length:
DC Resistance (R): Ω (at 20°C)


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Apr 192012

infoSingle layer air core inductor calculator.
Winding the wire in a single layer produces an inductor with minimal parasitic capacitance, and hence gives the highest possible self-resonant frequency (SRF). Striving to obtain a high SRF and low losses is the key to producing coils which have radio-frequency properties bearing some useful resemblance to pure inductance.
The calculation is based on Wheeler’s 1928 formula for a single-layer solenoid which is given in its original form as:
L = a² N² / (9a + 10b) [microHenries] , b > 0.8a
Where b is the coil length in inches, and a is the radius in inches.

To convert this formula to SI units, we will use the symbols r = radius, D = 2r = diameter, l = solenoid length.
Factoring b from the denominator gives:
L = 10-6 a² N² / [ b (10 + 9a/b)] [Henrys] The quantity a/b is dimensionless, and so we can immediately substitute in the denominator:
L = 10-6 a² N² / [ b (10 + 9r/l)] = 10-6 a² N² / [ b (10 + 4.5 D/l)] Factoring 10 from the denominator gives:
L = 10-7 N² ( a² / b ) / (1 + 0.45 D/l) [Henrys]


  • L is the inductance in Henry
  • D is the coil diameter in meters
  • r is the radius in meters (or D/2)
  • l is the lenght of the coil in meters
  • N is the number of turns
Please note that the accuracy of this formula is ±0.33% if the ratio of D/l>0.4. so this formula fits best for long solenoids.

noteThis formula applies at ‘low’ frequencies (<3MHz) using enameled copper wire (magnet wire) close wound.

Tip 1Small reductions in the inductance obtained can be achieved by pulling the turns apart slightly. This will also reduce self-resonance. Other combinations of wire and coil diameter may be tried but best results are usually obtained when the length of the coil is the same as its diameter.

Tip 2 If you need good induction stability in the presence of vibration then wind the coil on a support made from a suitable non magnetic plastic or ceramic former and lock the windings using epoxy glue or other suitable adhesive.

Please note that the diameter is measured from center of wire trough
center of the coil and to center of the wire on the opposite side.


Required Inductance (L):
Coil Diameter (D):
Wire Diameter (d):
Coil Length (l):
Number of Turns (N):


Apr 182012

Info This is an popular coil geometri used in todays wireless charger circuits.
The formula used in this calculation is based on the
Harold A. Wheeler approximations
for air core flat spiral coil inductor.


  • L = inductance in μH
  • Di = inner diameter in inches.
  • s = distance between windings in inches
  • w = wire diameter in inches
  • N = number of turns

1 inch = 0,0254m=2,54cm = 25,4mm.
This formula applies at ‘low’ frequencies (<30MHz)
using enameled copper wire. Some people call it "magnet

Click on image to enlarge

Flat spiral coil inductor example

Please note that the outer and inner diameter is measured from the center of the wire.
Flat spiral coil dimensions drawing


Coil inner diameter (Di):
Number of turns (N):
Wire Diameter (w):
Spacing between turns (s):
Inductance (L):
Outer diameter (Do):
Wire lenght (Wl):


More about spiral inductors..

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Apr 172012

Push image to enlarge
Square planar spiral coil Hexagon spiral coil inductor Octagon spiral coil inductor Sircular spiral coil inductor
InfoThe first approximation is based on a modification of an expression developed by Wheeler; the second is derived from electromagnetic principles by approximating the sides of the spirals as current-sheets; and the third is a monomial expression derived from fitting to a large database of inductors (and the exact inductance values).
All three expressions are accurate, with typical errors of 2 – 3%, and very simple, and are therefore excellent candidates for use in design and synthesis. The thickness of the inductor has only a very small effect on inductance and will therefore be ignored.
Fill in appropriate values in the white fields.Then push “calculate”.
1μm =0.001mm
1μm =0.00003937007874015748 inch
Number of turns (n): turns
Spacing between turns (s): μm
Turn width (w): μm
Outer Diameter (dout): μm
Calculated Inner diameter (Din) μm
Fill factor p=(Dout-Din)/(Dout+Din)
  Square Hexagonal Octagonal Circular
Modified Wheeler nH nH nH nH
Current Sheet nH nH nH nH
Monomial Fit nH nH nH nH


S.S. Mohan, M. Hershenson, S.P. Boyd and T.H. Lee
Simple Accurate Expressions for Planar Spiral Inductances
IEEE Journal of Solid-State Circuits, Oct. 1999, pp. 1419-24.
For multilayer spiral pcb coils see here:
A new calculation for designing multilayer planar spiral inductors

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Apr 152012

With the emphasis today on the need for more efficient and cost-effective power solutions, EE-Times created this column to provide helpful tips on a variety of power management topics. This column is geared towards design engineers at all levels. Whether you’ve been in the power business a long time or just coming on the power scene, you’ll find some nuggets of information that just might help you with your next design challenge.

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Apr 132012

This page is an Electronics Design Check list. It was
originally obtained from a HP document. It has been
extensively adapted to suit my and hopefully other design
engineers requirements. Copy it and edit it as you
see fit. Some checks are done automatic with most schematic
and pcb layout software, but serve as reminders.


Drawing Basics

1. Use a suitable universal file name for schematics,
and backup the file. Consider how useful “new_powersupply.scm”
will look in a few years.

2. Title block completed on all schematic and other

3. Check pin numbers of all custom-generated parts.
Especially check the rotation direction on footprints,
considering surface mount and DIP can be confusing.
Pinout may vary between DIP and various SMD packages.

4. Check power and ground pins of devices. Check supply
voltages as well as supply types are used appropriately
(battery, switched, ref_1V ).

5. Check hidden power and ground connections – or don’t
use them.

Device Rules

1. Unused CMOS inputs should always be pulled up or
down. Consider logic pins not connected directly to
power or ground but use resistors for in-circuit testing
and modifications.

2. Spare connector and IC pins accessible on prototype
boards, just in case. Use resistors to tie them to ground
so connection points are available.

3. CMOS gates always operated by logic levels at the
rails to minimize current.

4. No outputs joined together except open collector
(collector or drain ORed).

5. Inputs have current limiting resistors to protect
against expected voltages.

6. Outputs have current limiting to protect against
shorts and can supply expected currents.

7. Logic circuits not loaded inappropriately (to non
logic levels).

8. Open collector outputs have on board pullups. Check
that output pullup voltage is not restricted unexpectedly
by internal clamp diodes to the power rail.

9. Minimize opamp loads, especially LM324 and LM358
outputs loaded lightly to prevent distortion as the
device switches to higher current mode. (< 50 microamps,
and provide DC load to common).

10. Ensure inputs of unused opamps are not left floating,
and the amplifier is configured appropriately (so it
cannot oscillate).

11. Check time delays and slew rates of opamps used
as comparators.

12. Use current limiting resistors on opamp inputs always
(1 mA).

13. Check common mode input voltage range on opamps.
It is not always rail to rail.

14. Check failure modes and effects of failed power

15. Devices with quasi-bidirectional ports must not
have pull down resistors attached – they can toggle
the state.

16. Use hard pulldowns to get a low (< 1 K), or add
stronger pullup resistor. Make sure inputs cannot be
driven by hard voltage.

17. Consider grounding any crystals used on the board
to proper ground to reduce EMI.

I/O Connectors

1. External connections filtered for RFI and expected
voltages. Use ferrite beads for VHF, 100 ohms and 1
nF for RS232 and appropriate values for other lines
or sensor inputs. No capacitors on amplifier outputs
unless isolated by appropriate series impedances.

2. External I/O lines have a defined state when unplugged
(pullup or pull down).

3. Make sure I/O devices can handle unknown outputs
(usually inputs with weak pullup to high) until the
reset is over.

4. Consider making all external digital inputs active
low. Outputs may be either polarity but consider startup.

5. Consider connectors where ground made first and breaks
last for hot pluggability. Phono plugs are an example.

Digital Circuitry

1. Check setup, hold, and access times for data and
address bus.

2. Check capacitance and fan out limits for bus.

3. Check the data sheet and notes for unfamiliar ICs.
Read the small print and also in between the lines.

4. Search for meta stable states such as a 2 gate latch
which can be set and reset at the same time with an
indeterminate result. Other causes are clocked circuits
with runt clock pulses (too short or too low), or slow
rise time clock pulses. The result may be loss of timing
due to non logic levels, delayed state change or inappropriate
states, causing system failure. ‘Slack’ timing available
on clock pulses is an issue in reducing the adverse

5. Search for timing races where glitches can be generated.
An example is where two signals on different inputs
of a gate change at almost the same time (1 – 100 ns).
The logic can generate brief glitches. An example is
with decoders like 74HC138 which have several inputs
changing close together and can generate a burst of
glitches. Some will be ‘runt pulses’. These are best
used in systems with a latch or gate to enable the output
when the data has settled.

6. A reset circuit may be required to reset devices
to an appropriate state at power up.

Power Supplies

1. Power supply filtering adequate, so input does not
approach regulator dropout at lowest supply and full
load ripple.

2. Rectifier diodes always add reverse recovery spikes
that pass through regulators. These usually end up as
10 mV noise pulses at line rate. Filter them with inductors,
resistors and capacitors as required. Snubbers across
diodes may help reduce radiation.

3. Use mains transformers with electrostatic shields
for really low noise systems. Plugpacks will usually
not suffice.

4. Power supply reservoir should be adequate, providing
a holdup time at least 200 ms at full load and lowest

5. Device supply decoupling adequate (especially CPU,
memory devices). Consider adding series impedances for
best decoupling.

6. Use power supply polarity reversal protection. This
also ensures regulator cannot be destroyed by shorted
input (battery leads).

7. Regulators have supply capacitors bigger than total
load capacitance for protection against reverse bias.

8. Sufficient stabilizing capacitance on low dropout
voltage regulator outputs.

9. Consider cascaded regulators can have high current
states. Check them by slowly reducing the power below
minimum system voltage (until the regulators drop out)
while monitoring the current.

10. Solenoids and other inductive devices can generate
destructive voltages. Absorption circuits may simply
dump the spike on the power supply. The power supply
may not absorb them if it is a lightly loaded series
regulator. Even large batteries may not absorb the spike
if it has enough energy. The inductive device needs
snubbers and reverse clamps directly across it, not
just across the switch device. The power supply may
need to be appropriately clamped. Consider cars have
up to 100 V spikes normally!

11. Check operating voltage range of overall system
(low battery condition).

12. Consider fuses carefully, keeping in mind they protect
from fires, and protect the supply, not the load.

13. Check any devices that power down are isolated from
devices that remain powered up. Use open collector or
tristate interface devices with hardware operated control
line as appropriate.

14. Estimate total worst case power supply current,
and check that circuit operation agrees.

Discrete Components

1. Voltage ratings and polarities of components checked.

2. Check polarized coupling capacitors cannot get reverse
voltage. Eliminate polarized capacitors where possible.

3. Check if undervoltage and overvoltage protection
is required.

4. Use over rated tantalum capacitors for longer life.

5. Amplifiers checked for stability.

6. Oscillators checked for reliable startup and within
reset time of clocked systems like microprocessors.

7. Check heatsinking requirements for maximum power
dissipation and worst-case operating temperatures.

8. Allow a wide safety margin for resistor power dissipation
(< 1/3 rating). They can easily melt solder or char

9. Keep reverse base-emitter current/voltage on bipolar
transistors low (use diode clamps).

10. Check for voltage transients and high voltages on
FET gates. Clamp gates of FET circuits to keep within
ratings. Check that FETs biased at non digital levels
have “gate stoppers” to limit high frequency
response and prevent parasitic oscillation.

11. Protect collectors/drains from fast risetime pulses
that may cause inductance in leads and loads to generate
damaging high voltage spikes.

12. Consider signal rate-of-rise and fall for noise

13. Separate analog signals from noisy or digital signals.

14. Surge current magnitude through semiconductors within

Reset and Supervisory

1. Reset circuit designs must be reliable, both glitch-free
and consistent; tested with fast and slow power supply
rise and fall time. The capacitor type is inferior –
consider comparator types, but test them carefully for
low voltage behavior.

2. Check reset behavior when power supply cycles before
the circuit is fully operational.

3. Consider watchdog timer testing, disabling and diagnostics.

4. Monitor power supply operation during shutdown and
startup and supply on-off cycling.

Printed circuit board (PCB)


1. Copyright notice on PCB in copper.

2. Date code on PCB in copper.

3. PCB ID number and layer number on each layer in copper.

4. Drill legend – what sizes are used?

5. Netlist check – automatic and manual. Look for nets
with single nodes or too many nodes.

6. Design rule check. A manual version can find problems
missed by automatic checks.

7. Check for dead-end traces.

8. Ensure schematic software did / did not separate
Vcc from Vdd, Vss from GND as needed.


1. When determining board size go for a larger board
within reason. This decreases time to layout or auto
route, populate, debug and maintain. Small size is cute
but not always needed.

2. Consider PCB manufacturing panel sizes when deciding
on PCB sizes. (Minimize wastage of PCB’s per panel).

Holes on layout are probably finished sizes, after plating.

3. Finished hole sizes are >=10 thou larger than
the lead, or larger spec dictated by automatic insertion

4. Pads >=15 thou larger than finished hole sizes.

5. Place thru hole components on 50 thou grid.

6. All components >= 0.2″ from edge of PCB.

7. Silk screen legend text weight >=10 thou.

8. Check layout rules with your pcb manufacturer.


1. Are mounting holes electrically isolated or grounded?

2. Allow proper mounting hole clearance for hardware.
Allow space around them for stand off mounts, washers,

3. All polarized components checked.

4. No acute inside angles in foil.

5. No traces within 20 thou of PCB edge.

6. Serial number blank on silk screen legend.

7. Thru hole drill tolerance noted.

8. Thru hole solder mask tolerance noted.

9. Thru hole route tolerance noted.

10. Thru hole silk screen legend tolerance noted.

11. Use ground planes where possible.


1. Mounting holes matched 1:1 with mating parts.

2. All polarized components point same way.

3. Use but ensure there is minimum component body spacing.

4. Clearance for IC extraction tools.

5. Clearance for IC sockets (especially for during
proto phase). Sufficient clearance for socketed ICs.

6. Sockets used on devices prone to damage (near I/O

7. CPU devices usually socketed to allow bus testing,
emulator etc.

8. Visual references for automated assembly (future
auto placement).

9. Tooling holes for automated assembly (future auto

10. Tooling and mounting holes have internal plane clearance
to avoid multilayer shorts. (Expect the software to
look after this, but check it).

11. Ensure pin 1 interpretation and orientation consistent
among all connectors of a given type on the board.

12. All ICs have pin one marking visible when chip is

13. Standoffs on power resistors or other hot components.

14. Check power and ground connections to all ICs.

15. Check hole diameters for odd components: rectangular
pins, spring pins.

Tracks and EMI

1. Trace width sufficient for current carried, consider
trace heating especially on internal layers.

2. Thermal relief’s for internal power layers.

3. Clearance for high voltage traces.

4. Clearance and guards between noisy and quiet lines.
Noisy ones to note are the capacitors on negative rail
7661 chips, RS232 lines, digital lines and busses. Keep
noisy lines short.

5. Bypass capacitors located close to IC power pins.
Minimize loop areas of decoupling capacitors.

High frequency crystal cases should be flush to the
PCB and grounded so they don’t become an antenna.

6. Check for traces running under noisy or sensitive

7. Use guard tracks round high impedance and low noise
lines. Keep them short.

8. Component and trace keepout areas observed.

9. Digital and analog signal commons joined at only
one point.

10. Place I/O devices near where their signals leave
the board.

11. EMI and RFI filtering as close as possible to exit
and entry points of shielded areas, I/O connectors.

12. Provide multiple vias for high current and/or low
impedance traces.

13. Consider ground loops and voltage drops on tracks
– ground ain’t ground.


1. Provide a ground test point, accessible and sized
for scope ground clip.

2. Potentiometers should increase controlled quantity

3. Check the orientation of all connectors using actual

4. Silkscreen text located to be readable when the board
is populated.

5. No vias under metal-film resistors and similar poorly
insulated parts.

6. Check for traces which may be susceptible to solder


1. Assembly notes for all special operations such as
glue, inductors, clamps, brackets.

2. Conformal coating, and masking for it.

3. Special static handling precautions required during
assembly and test.

4. Wire size checked.

5. Cable ties or lacing cord shown where needed.

6. Color of wires.

7. Voltage drop at maximum current with specified wire
for entire current path (eg. power and ground).

8. Cooling requirements addressed.

9. Control of flexing, vibration and shock.


1. Use modular design.

2. Have a version number and change it every time the
software is modified. Have a note at beginning of software
explaining what has been done in this version.

3. Revision (version) history noted for all changes
(at top of source code)

4. Loops checked for exit conditions.

5. Communications and other ‘wait’ timeouts checked.

6. All branches tested.

7. Check for event showers, where one event causes other
events (e.g. a resize in a resize can cause a paint
and a resize, which causes more, until the stack is

8. Check for event lockouts (code running in a loop
prevents events being detected).

9. Check for interrupt showers (where one event causes
multiple interrupts.

10. Check stack size with maximum pushdown.

11. Avoid using the stack for variables if relevant,
due to the confusion in popping and pushing.

12. Use defined variables (‘option explicit’ in basic).

13. Avoid re-entrant code – it is too hard to debug
and understand.

14. Check the scope of variables. Global variables and
constants are defined in a special include file or module
if possible. Others may have local scope within a subroutine
or function or a module. In Visual Basic, variables
defined in a form are private to that form. Global variables
are defines in a module (.BAS) file, and can be read
by forms too.

15. Check any need for static variables. An example
is a ‘first-time’ flag. Global variables are static,
as they are stored in memory somewhere. Local variables
are dynamic, as they are stored on the stack for the
time the procedure is running only. They are temporary.

16. Event driven code, like interrupts, can be executed
any time. If global variables are set by this code and
used in other processes it is possible for meta stable
states to exist. The variable may be changed by an event
elsewhere while it is being processed. Protect against
this by having copies, multiple reads compared to make
the copy, or proper handshake flags. An example is a
hardware real time clock. Copy the value and work with
the saved value, rather than reading the RTC itself
each step of a procedure.

17. Avoid multiple ‘IF’ statements – they are confusing
and hard to understand or test. Use case statements
instead, where appropriate.

18. Each process (subroutine, function) should be small
and simple to avoid misunderstanding. Consider more
than 25 lines of statements as ‘suspicious’.

19. Follow the concepts of structured programming, avoiding
‘spaghetti’ code that is difficult to understand.

20. Consider the differences between ‘for-next’, ‘while’,
and ‘until’.

21. CPU utilization measured, especially in critical
loops such as processing an ADC or signal processing
where real time response is needed.

22. Interrupt response time measured.

23. Interrupt execution time measured.

24. Naming conventions consistent and meaningful.

25. Adherence to coding style standards – others or
even you may have to debug it.

26. Build in debug aids for example a debug flag to
allow test files to be run to emulate I/O.

27. Power-up, power-down considerations.

28. Unused interrupt vectors trapped.

29. Unused ROM space loaded with trap or restart instructions.

30. Warm and cold reset differences.

31. ROM default, user setting, stored (non volatile)
user settings considered.

32. Nonvolatile memory corruption possibilities checked
during power-up, power-down, and program-gone-wild conditions.

33. Adequate comments and design notes in code. Explain
I/O, steps being taken in global terms, not in terms
of ‘load R8′. Have a software manual or topic in the
technical manual if additional notes required.

34. Check for FIFO and buffer overruns.

35. Check critical timer driver code, timer event driven

36. Check for odd address usage on 16/32 bit micros,
especially an odd stack pointer

37. Use a standard reminder flag and check for any flagged
statements in software.

Test and Maintenance

1. Test points on PCBs for critical circuits, hard to
reach nets.

2. Test pads on a regular grid for (future) in-circuit
or bed-of-nails functional testing.

3. Test and calibration procedure written before production

4. Special test arrangements and connectors for testing
– provide schematic and describe in test procedure.

5. Easy disassembly and reassembly

6. Fuses accessible and labeled

7. Self test mode – software has built in procedures
such as analogue and digital I/O commands to aid in

8. Spare parts available.

Event logging of exceptional conditions.

1. Thermal cycling excursions internal to components
and assemblies within acceptable limits.

2. Capacitors mounted below or away from heat-dissipating
devices such as transformers.

3. Consider test aids on board such as test signal source,
switches, pushbuttons and status LEDs on PCB or elsewhere.

4. Provide test routines in software so commissioning
is automated where possible. Examples are memory test,
activity LED, watchdog test and disable, I/O tests.
Others are battery backup, RTC, non-volatile memory,
special test cycles.

5. Defaults for switches and settings that make the
system work in some defined way.

6. Error messages to indicate what problems the software
has found.

Safety and Environment

1. Remember electronic failures are due to bad environment.

2. EMC addressed, but in some cases special consideration
required for emission or susceptibility – eg a data
logger to work on the deck of a vessel must have RADAR

3. Resistance and tolerance of entire unit to static
discharge via any path

4. Vibration tolerance of entire assembly and individual

5.Protection against liquids and foreign objects

6. Clear safety warnings in manual and wherever hazards
exist. Control these hazards.

7. Fuse and circuit breaker size and characteristics

8. Fuse sizes marked near fuse holder

9. Room to remove fuse without damaging other components
– warning to remove power.

10. Spare fuse storage

11. Shock hazards

12. Radiated energy warnings and shields

13. Applicable standards checked


This topic was developed for equipment intended for
in house use, not for sale to others. A system being
marketed would need further steps for EMC and other
compliance, contact info, parts lists, warranty and
so on.

On developers workstations, use readily located directories
for software, user manuals and other documentation.
They should be project oriented.

Use a paper file folder during project development phase.
There is still some stuff that isn’t on a computer.

Use the internal website for final project information
stored in systems knowledge base. This allows users
and Engineering staff to download their own manuals
and other information. Have a separate area for each
project. Use html files designed so relevant parts (e.g.
manuals, checklists) can be printed.

User Manual: how to use, specification, field problem
solving, operational checklists, tips and procedures.

Service manual: commissioning, calibration and test procedures,
design notes as appropriate.

Calibration sheet template in word processor format.
Used to enter test results.

Test and calibration results for QA documentation, accessed
from project area of web site or stored as paper file
and referenced from website.

Information that may be lost if individuals depart the
organization – both computer and physical paper files
properly archived (CDROM).

Software source code archived (CDROM), with zipped executable’s
or other target files linked from internal web site
(software area). This allows users to download and install
their own software.

Correct all errors found in schematics, layouts and


Get others to test the device, especially the end user.

Compare the original purpose and project definition
with the end results.

Test that the specification is met, especially key
items like accuracy, deployment, speed, operational
resources (battery and memory reserves).

Make sure users understand special needs and instructions,
and have been advised about hazards, where to get help,
manuals etc.

Ensure that default conditions and configurations are
such that a system will work immediately the user turns
it on, or at least explain what to do next.

Ask users if they are satisfied.

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Apr 122012

Texas Instruments (formerly Unitrode) seminars are part of TI analog technical training during which they also update on their new controllers and other power management integrated circuits. They combine tutorial review of basic principles and “hands-on” design examples on various power conversion topics. Over time they have covered virtually all important switching power supply design topics and their archives provide excellent reference info for the SMPS designers. Here you will find seminar books from 1984 till present.

SEM300 (1984)

Switching Power Supply Topology Review

Closing the Feedback Loop

Appendix A: Error Amplifier and Compensation Network Design

Appendix B: Bode Plots

Appendix C: Flyback-Discontinuous Inductor Current-Direct Duty Cycle Cont.

Switching Power Supply Design Review — 60 Watt Flyback Regulator

Appendix I: Transformer Design

Appendix II: Effective RL and C in the Feedback Loop

SEM400 (1985)

Current-Mode Control of Switching Power Supplies

Design of Flyback Transformers and Filter Inductors

Simulation of Switching Power Supply Performance Using the Personal Computer

Design Review: 150 Watt Current-Mode Flyback

Power Conversion Design Guide

SEM500 (1986)

Practical Considerations in Current Mode Power Supplies

The Effects of Leakage Inductance on Multi-Output Flyback Circuits

Coupled Filter Inductors in Multi-Output Buck Regulators

A 300W, 300KHz Current-Mode Half-Bridge Converter with Multiple Outputs

The Right-Half-Plane Zero — A Simplified Explanation

Magnetic Amplifier Control for Simple, Low-Cost, Secondary Regulation

SEM600 (1988)

Resonant Mode Converter Topologies

1 MHz 150W Resonant Converter Design Review

High Power Factor Preregulator for Off-Line Power Supplies

Placing Leakage and Wiring Inductances in the High Frequency Circuit Model

SEM700 (1990)

Zero Voltage Switching Resonant Power Conversion

Isolating the Control Loop

Average Current Mode Control of Switching Power Supplies

Resonant Mode Converter Topologies — Additional Topics

Optimizing the Design of a High Power Factor Switching Preregulator

SEM800 (1991)

Load Sharing with Paralleled Power Supplies

Controlled ON-Time, Zero Current Switched Power Factor Correction Technique

Fixed-Frequency, Resonant-Switched PWM w/ Phase Shifted Control

Considerations in High Performance MOSFET, IGBT, and MCT Gate Drive Ckts.

Control Loop Design

SEM900 (1993)

Distributed Power Systems

Snubber Circuits: Theory, Design and Application

Designing a Phase Shifted Zero Voltage Transition Power Converter

Design Review: 500 Watt, 40W/in3 Phase Shifted ZVT Power Converter

High Power Factor Preregulator Using the SEPIC Converter

Control Loop Design SEPIC Preregulator Example

Coupled Inductor Design

SEM1000 (1994)

250KHz, 500W Pwr Factor Correction Ckt. Employing Zero Voltage Transitions

Portable Power — A Designer’s Guide to Power Management

Active Clamp and Reset Technique Enhances Forward Converter Performance

An Electrical Circuit Model for Magnetic Cores

SEM1100 (1996)

Fueling the Megaprocessors – Empowering Dynamic Energy Management

100W, 400kHz, DC/DC Conv. w/ I Doubler Sync. Rectification Achieves 92%

Design Considerations for Active Clamp and Reset Technique

Control Loop Cookbook

SEM1200 (1997)

Current Sensing Solutions for Power Supply Designers

A Low Power Boost Converter for Battery Powered Portable Applications

A Unique Four Quadrant Flyback Converter

Design Review: 140W, Multiple Output, Very High Density DC/DC Converter

SEM1300 (2000)

Cascaded Power Converter Topology for High Current Low Output Voltage App.

Hot Swap Power Management

50W Forward Converter w/ Sync. Rectification and Secondary Side

Frequency Response Measurements for Switching Power Supplies

A More Accurate Current-Mode Control Model

SEM1400 (2001)

An Analytical Comparision of Alternate Control Techniques

Design and Application Guide for High Speed MOSFET Gate Drive Circuits

Appendix A: Estimating MOSFET Parameters from the Data Sheet

Magnetic Field Evaluation in Transformers and Inductors

High-Efficiency, Regulated Charge Pumps for High-Current Applications

Designing Stable Control Loops

Internal Compensation – Boon or Bane

Implication of Sync. Rectifiers in Isolated, Single-Ended, Forward Conv.

SEM1500 (2003)

Topic 1: Understanding & Optimizing Electromagnetic Compatibility in…

Topic 2: Designing High-Power Factor Off-Line Power Supplies

Topic 3: Achieving High-Efficiency w/Multi-Output CCM Flyback Supply…

Topic 4: Transformer & Inductor Design for Optimum Circuit Performance

Topic 5: Under the Hood of Low-Voltage DC/DC Converters

Topic 6: Paralleling Power–Choosing & Applying the Best Technique for…

SEM1600 (2004)

Topic 1: Safety Considerations in Power Supply Design

Topic 2: Sequencing Power Supplies in Multiple Voltage Rail Environments

Topic 3: Design Review: A Step-by-Step Approach to AC Line-Powered Converters

Topic 4: Constructing Your Power Supply – Layout Considerations

Topic 5: Interleaving Contributes Unique Benefits to Forward & Flyback Converter

Topic 6: A Practical Introduction to Digital Power Supply Control

Topic 7: Compensating DC/DC Converters with Ceramic Output Capacitors

SEM1700 (2006/07)

TOPIC 1: Improving Power Supply Efficiency – The Global Perspective

TOPIC 2: Green-Mode Power by the Milli-Watt

TOPIC 3: Feedback in the Fast Lane–Modeling Current-Mode Control in High-Frequency

TOPIC 4: Designing Planar Magnetics

TOPIC 5: An Interleaved PFC Preregulator for High-Power Converters

TOPIC 6: Software Design for Digital Power – Programming 101 for Analog Design

TOPIC 7: Designing a Digital Telecom Rectifier

SEM1800 (2008/09)

Topic 1 – High Power Factor and High Efficiency…You Can Have Both

Topic 2 – Understanding Noise-Spreading Techniques and their Effects

Topic 3 – Under the Hood of a DC/DC Boost Converter

Topic 4 – Improving System Efficiency with a New Interm.-Bus Architecture

Topic 5 – High-Voltage Energy Storage: The Key to Efficient Holdup

Topic 6 – Using PMBus™ for Improved System-Level Power Management

Topic 7 – Applying Digital Technology to PWM Control-Loop Designs

This is the end of page

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