Xflighttech XF-160GL3 Instruction Manual
Xflight Technologies LLC
XF-160GL3 Lightning Pulse Generator
Data sheet and User Guide
Version 1.2
March 2020
Xflighttech.com
Copyright © 2020 Xflight Technologies LLC, Florida, USA
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XF-160GL3 Specifications
Item
Value
Unit
Unit length
220 (8.67)
mm (inch)
Unit width
150 (5.90 )
mm (inch)
Unit height
64 (2.52)
mm (inch)
Unit weight
0.78 (1.85)
Kg (lbs)
Enclosure material
ABS plastic / FR-4 TG130
-
Battery requirement (Batteries not provided)
X6 1.2V (AA)
V
Current consumption (quiescent)
300
mA
Total power consumption (quiescent)
2.2
W
Battery polarity protection
Yes
Safety cut-out switch
Yes (Optical)
Output Pulse Terminals (material)
Brass
-
Output Pulse Terminals (type)
4mm Banana plugs
-
Max O/C peak voltage
400
V
Max S/C peak current
60
A
Current Measurement Bandwidth
400
KHz
Current Measurement Sensitivity
25
mV / Amp
O/C voltage rise time (@ 300V)
5.3 ± 10%
s
O/C voltage fall time to half peak(@ 300V)
72 ± 10%
s
S/C current rise time (@ 60A)
3.4 ± 10%
s
S/C current fall time to half peak (@ 60A)
59 ± 10%
s
Output Impedance
5
DO-160G WFs for current and voltage
1 and 4
-
DO-160G levels for voltage and current
1, 2 and 3
-
Unit protection against external voltages (TVS)
>567
V
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A. Introduction
The XF-160GL3 produces a double exponential voltage / current pulse intended to give
confidence that a design can pass DO160G and MIL-STD-461G conformance / Qualification
tests. DO160G is the RTCA Inc. Environmental Conditions and Test Procedure for Airborne
Equipment. It is a very important aviation industry specification and used throughout the
industry to qualify any equipment prior to it being allowed to fly on commercial aircraft.
Section 22 relates to Lightning Induced Transient Susceptibility testing. It defines certain
waveforms that must be applied to any unit under test (UUT). Two types of application of
simulated lighting energy are described.
(i) Induced. This is where the energy it transferred to the UUT via induction into cables
connecting signals and power to the UUT. (The cabling to be as similar to a real
installation as possible).
(ii) Direct pin injection. A test probe is connected, in turn, to each connector pin that
allows any signal or power line to connect the unit to the aircraft.
Of the two cases above the direct pin injection is considered to be the worst case since all
the energy is concentrated onto a single pin / signal. Furthermore, of the different types of
waveform, the one considered to be the worst case is the double exponential (see appendix
A(5)(b). The rise time and fall time of the pulse is important. This defines the pulse width
and so the amount of energy that can be transferred to a UUT. For high impedance signals
that effectively deflect the energy back to the source, the pulse width defines for how long
a high voltage is present on the interface. The XF-160GL3 supports a waveform very similar
to the DO-160G waveform 1 (WF1) and waveform 4 (WF4). WF1 is a current waveform for
low impedance signals where it is not possible to meet the voltage requirement. WF4 is the
voltage waveform.
DO160G defines different levels of energy (Level 1 being the weakest and level 5 the
strongest). The level needed depends primarily on the equipment function (i.e. critical or
not) and the installation location. (There is also a dependence on any electrical connections
to other parts / equipment on the aircraft).
The XF-160GL3 allows for confidence testing of WF1/4 to level 3 as shown below.
Level
Voc / Isc for WF4/WF1 *
Comments
1
50 / 10
50V peak / or 10A peak
2
125 / 25
125V peak / or 25A peak
3
300 / 60
300V peak / or 60A peak
* Voc is peak open circuit voltage. Isc is peak short circuit current.
Level 3 waveforms and levels are generally for non-critical equipment inside the aircraft,
such as in the Electronics bay.
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The waveform shape is shown below. The rise time is defined as the time to reach the
peak voltage (or current). The decay time is defined as the time to fall back to half the
peak voltage (or current).
6.4
s / 69
s DO160G pulse(WF4)
Vpk
Vpk / 2
6.4μs 69μs t
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The XF-160GL3 main functions
B. Terms, Conditions and Warranty.
This product is only intended to be used for testing of electronic assemblies and units to
gain confidence in the design prior to any formal conformance or qualification testing.
See Appendix D for details
On / Off button
HT voltage
adjust to set
pulse peak
Press to Arm, passes
high voltage to output
stage
Set for current
waveform (S/C)
operation or voltage
waveform (O/C)
operation
Press to send pulse
out onto the output
connectors
White LED lights
up momentarily
as pulse is
output
Displays high
voltage available
(not pulse peak
voltage)
Green LED
means power is
on
Pulse outputs –
connect to UUT
Outside screws (x6)
to change batteries
Pulse current WF
(internal magnetic
field measurement)
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C. Safety.
When switched on, this product generates high voltages internally and outputs a high
voltage pulse. There are two areas where care should be taken. One is in normal operation
when a pulse is output from the output terminals, the second is when the unit is opened to
change the batteries. These cases will be detailed here in more detail.
Normal operation
In normal operation the output pulse width is less than 1ms in duration, however the
voltage can be set to an output in excess of 300V. Hence care should be taken not to touch
the output connections when the pulse button is pressed.
Changing the batteries
The internal electronics utilizes high voltage capacitors to store charge, hence it’s very
important not to open the unit while it is switched on. Before opening the unit it should be:
Set to a voltage of less than 50V.
Or it should be switched off and:
Left for at least one minute before opening it up.
Momentarily switching back on will confirm the voltage is at a safe level.
The following precautions have been designed into the XF-160GL3 Lightning Pulse
Generator to mitigate any danger to an operator.
(i) A safety cut-out switch makes sure the power is cut to the unit when the internal
assembly is lifted out of the box in order to change the batteries. This is a light
activated cut-out.
(ii) When power is cut from the internal assembly printed circuit boards any high
voltages still present will dissipate naturally to safe levels within 50 seconds.
(iii) Any high voltage areas within the internal assembly printed circuit boards are
covered in protective insulating material to prevent conduction in case of
accidental contact.
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D. Description.
1. On / Off switch: Powers up the XF-160GL3 ready for operation.
2. Power On LED: The green LED shows that power is on.
3. Voltage adjust knob: Allows the High Tension (HT) voltage to be set. This is not the
peak output pulse voltage, but a voltage used to drive the pulse
generation circuitry.
4. Volt Meter: Allows the HT voltage to be set and so the final output peak pulse
voltage can be estimated.
5. Arm Button: Momentarily pressing this Arm button arms the pulse generator
circuity. For safety reasons the pulse generator circuitry will start
to lose this voltage with time and so the fire button needs to be
pressed within seconds after arming to maintain the required
peak pulse voltage.
6. Arm LED: The orange Arm LED indicates that the XF-160GL3 has been armed
and ready to fire.
7. WF Switch The WF (Waveform) switch must be set to either I for the current
waveform, or V for the voltage waveform, prior to either
Switching on, Arming or Firing.
8. Fire Button: The fire button generates the double exponential transient pulse.
Once fired, the unit must be re-armed.
9. Fire LED: The white Fire LED illuminates for the very short period the pulse
is active.
10. Current WF These test points are to monitor the current waveform. This is
achieved by measuring the magnetic field as the pulse is
generated and output. This gives a good indication of the current
waveform, even if the connected UUT represents an inductive
load. (The output is 25mV per Amp with 400KHz bandwidth).
Note on Calibration
The XF-160GL3 itself does not need calibration. If it is required to use the unit as part of a
formal qualification procedure this can be done by measuring the output pulse with a
calibrated oscilloscope (under known and measured ambient conditions, e.g. temperature,
humidity and airflow).
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E. Setup and Operation
Power Source
The XF-160GL3 requires x 6 AA 1.2V batteries. It is recommended that high mA
rechargeable batteries are used; such as 2500mA. Typically the XF-160GL3 draws
approximately 300mA, (about 2.2 Watts of power), this would then give approximately 50
hours of continual use.
It is important to ensure the XF-160GL3 is switched off prior to installing / changing the
batteries. An internal, light activated, auto cut-out switch will remove power to the unit
when the assembly printed circuit boards (PCBs) are removed. However it is recommended
to switch off and wait at least one minute before opening up the unit.
Operation
The XF-160GL3 is capable of providing both positive and negative going pulses. (It is a
requirement of DO-160G to subject the UUT to both positive and negative pulses).
Positive Voltage Pulse Operation
Follow the following procedure for injecting a positive voltage pulse:
Step 1: Confirm Operation of the XF-160GL3 in stand-alone mode
1. Connect an oscilloscope between the Positive (+) and the negative (-) output pulse
terminals. Take care to ensure no damage to your oscilloscope with high voltages. (It is
usually recommended to use the x10 probe settings to measure high voltages.
Alternatively, construct a simple voltage divider with two resistors).
2. Turn the voltage adjustment knob fully anti-clockwise (i.e to the off position).
3. Slide the I/V selector switch to the V setting.
4. Switch the XF-160GL3 on, ensuring the green LED illuminates.
5. It will take some 30 seconds or so for the internal voltage to build up. After this time it
will be possible to set up a voltage using the adjustment knob. Slowly adjust the voltage
adjustment knob until the desired voltage is seen on the display, then wind back ¼ turn
or so until the voltage is stable. Note that the HT voltage approximately relates to an
output pulse peak voltage level as indicated in the chart below.
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6. Momentarily press the Arm button and ensure the orange LED illuminates when this is
done. Release this button after a very brief time of a second or so.
7. As soon as possible after releasing the Arm button press the Fire button. Note the pulse
on the oscilloscope.
8. Repeat the above procedure until the voltage trace on the oscilloscope is what is
required. Note, when adjusting the voltage knob, as soon as the desired voltage is
approached, start to wind back the knob to stabilize the voltage. You now know what
voltage to adjust next time, to produce the desired output pulse.
Step 2: Apply the XF-160GL3 pulse to the UUT
9. Connect short 4mm banana plug leads as follows
a. Negative Pulse output to the UUT ground
b. Positive Pulse output to the UUT signal to be tested
10. Switch the XF-160GL3 on, ensuring the green LED illuminates
11. Repeat the procedure of Step1 above to output a pulse
Negative Voltage Pulse Operation
12. The procedure is exactly the same as above for the positive pulse with the connections
being reversed, i.e.
13. Connect short 4mm banana plug leads as follows
a. Positive Pulse output to the UUT ground
b. Negative Pulse output to the UUT signal to be tested
0
100
200
300
400
500
600
050 100 150 200 250 300 350 400
HT Voltage
Output Pulse Peak Voltage
HT Voltage Vs Output Pulse Peak Voltage
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Positive Current Pulse Operation
Follow the below procedure for injecting a positive current pulse:
Step 1: Confirm Operation of the XF-160GL3 in stand-alone mode
1. Short circuit the Positive (+) pulse and the negative (-) output pulse terminals with a
wire of at least 18 AWG thickness.
2. Connect an oscilloscope between the Positive (Pos) Current WF test point and the
negative (Neg) Current WF test point terminals.
3. Turn the voltage adjustment knob fully anti-clockwise (i.e to the off position).
4. Slide the I/V selector switch to the I setting
5. Switch the XF-160GL3 on, ensuring the green LED illuminates
6. It will take some 30 seconds or so for the voltage to build up. After this time it will be
possible to set up a voltage using the adjustment knob. Slowly adjust the voltage
adjustment knob until the desired voltage is seen on the display, then wind back ¼ turn
or so until the voltage is stable. Note that the HT voltage approximately relates to an
output pulse peak current level as indicated in the chart below.
7. Momentarily press the Arm button and ensure the orange LED illuminates when this is
done. Release this button after a very brief time of a second or so.
0
100
200
300
400
500
600
010 20 30 40 50 60 70
HT Voltage
Output Pulse Peak Current (Amps)
HT Voltage Vs Output Pulse Peak Current
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8. As soon as possible after releasing the Arm button press the Fire button. Note the pulse
wave shape on the oscilloscope. 25mV corresponds to a current of 1 Amp. If the current
waveform is to be acquired with calibrated equipment, or simply to more accuracy, an
external current clamp can be used. (This is preferable to a simple low inductance sense
resistor for current measurement).
9. Repeat the above procedure until the current trace on the oscilloscope is what is
required. Note, when adjusting the voltage knob, as soon as the desired voltage is
approached, start to wind back the knob to stabilize the voltage. You now know what
voltage to adjust next time, to produce the desired output pulse.
Step 2: Apply the XF-160GL3 pulse to the UUT
10. Remove any short circuit wire between the pulse outputs
11. Connect short 4mm banana plug leads as follows
c. Negative Pulse output to the UUT ground
d. Positive Pulse output to the UUT signal to be tested
12. Switch the XF-160GL3 on, ensuring the green LED illuminates
13. Repeat the procedure of Step1 above to output a pulse
Negative Voltage Pulse Operation
14. The procedure is exactly the same as above for the positive pulse with the connections
being reversed, i.e.
15. Connect short 4mm banana plug leads as follows
a. Positive Pulse output to the UUT ground
b. Negative Pulse output to the UUT signal to be tested
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F. Maintenance
Changing the Batteries
If the unit is switched on, adjust the voltage to less than 50v. If the unit is off make sure it
has been off for at least one minute.
Unscrew the six screws closest to the edge of the XF-160GL3 box. Slowly lift the board
assembly up and out of the box, making sure not to unnecessarily poke fingers in-between
the boards or touch any of the board electronic components.
Install the batteries making sure the positive and negative terminals are correctly aligned.
Install the printed circuit assembly back in the box, ensuring not to accidentally power on
the unit.
Re-install the screws firmly, securing the top back onto the XF-160GL3 unit.
Power the unit on and note the green LED illuminates thus ensuring the batteries are
correctly installed. (The unit will not be damaged if the batteries are incorrectly installed).
Long term storage
If storing for a long period of time ensure the batteries are first removed.
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Appendix A
TVS Protection Application Notes
1. Testing generally tries to ensure any equipment can withstand two types of stress:
a. A fast rise time to a high voltage followed by a more prolonged fall time from
that voltage. This is a good test of Insulation strength.
b. A high Current pulse is a good test for current / fusing withstanding capability.
2. Typical protection solutions include the addition of a TVS (Transient Voltage
Suppression) diode. However care needs to be taken to select the most appropriate TVS
and related components. This application note points out how these calculations are
done under the two conditions of
a. Low impedance UUT interface
b. High impedance UUT interface
3. The first thing to know in detail is the signal requirements of a particular interface. The
following questions will then need to be answered:
a. Is the frequency of the signal so high that capacitive effects need to be
considered?
b. Can the interface cope with a series resistor to effectively reflect back as much of
the pulse energy as possible? I.e. would a resistor unduly affect a signal’s high /
low switching thresholds, and put these out of spec.?
c. What power and voltage levels should the TVS support?
d. Is the TVS to be a uni-directional one or a bi-directional one?
e. What type of technology and power / voltage levels should any series resistor
have?
f. What type of PCB layout should be considered?
4. The above is not an exhaustive list, but it does cover the most important issues. This
application note will try to answer the above questions by giving guidance as to how to
tackle the questions.
5. We’ll start by going down the list from (a).
a. Is the frequency of the signal so high that capacitive effects need to be
considered?
The signal needs to be considered. If the signal is simply a low speed clock, or a
simple voltage level, high or low then capacitance is generally not a problem. A
TVS has a certain intrinsic junction capacitance associated with it. It is also
dependent on the reverse stand-off voltage and whether it is a uni or bi
directional device. More details on the TVS later.
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If the signal is a high speed Ethernet signal then the capacitance would more
than likely kill the signal. In this case very low capacitance gas discharge tube
(GDT) technology can be considered. However there may then be issues of
longevity associated with such a design. GDT’s tend to be specified for only a
certain number of strikes / triggers before they start to degrade. For DO-160G
Level 3 a good magnetics device ought to be fine.
b. Can the interface cope with a series resistor to effectively reflect back as much
of the pulse energy as possible?
We will now consider only DC level or slow frequency signals. Any series resistor
will act as a voltage divider with the impedance of the signal interface, be that an
input or an output. As such any change in signal level will need to be calculated
to make sure that a resistor will not put the triggering thresholds out of spec.
Generally even a small resistor of say 100Ω will make a big difference to the type
of TVS that can then be used. A resistor of some 100KΩ or so will be even more
effective. The larger the resistor that can be added the better. The following
chart shows the effect of the resistor.
The above chart shows the energy to dissipate by the UUT comparing the two
pin injection cases at DO-160G level 3. At this level a double exponential pulse
(long dashed line) must be applied with a peak voltage of 300V. And a 1MHz
decaying Sine wave (short dashed line), at peak voltage of 600V. As can be seen
above the double exponential contains much more energy: A factor of 23 more
in fact! This is why we term the double exponential as the worst case. The
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
050 100 150 200 250 300 350
Energy in Joules
Rs in Ω
Energy to dissipate vs series resistance
Double exponential (6.4/69
s@ 300V peak)
Half SIne (single pulse 1MHz @ 600V peak)
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equations used to calculate these pulse energies are detailed in Appendix B.
c. What power and voltage levels should the TVS support?
This is where things become interesting! The first thing to note is the DO-160G
level to which the interface must adhere. The table below shows the possible
levels for the ‘worst case’ waveforms WF4 and WF1:
Level
Voltage WF 4 (O/C Volts)
Current WF 1 (S/C Amps)
1
50
10
2
125
25
3
300
60
4
750
150
5
1600
320
Amplitude tolerances are +10%, -0%
Note the XF-160GL3 does not support levels 4 and 5.
The double exponential pulses are defined as:
Temporal tolerances are +20%, -20%
Above is known as a 6.4/69
s pulse.
If no series resistor where to be employed on the interface and if a TVS were to
be specified as supporting the above waveform at the required voltage and
current waveforms then there would be no problem (provided also that PCB
space and component cost are not big issues). However, some data sheets show
an adherence to a 10/1000s pulse with certain peak current. Other devices
such as resistors show the maximum power it can withstand. We need to find a
good way to compare requirements vs component capabilities. Regarding a
t
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maximum voltage this is easy to do, but regarding the current waveform it is
necessary to calculate how much energy is to be dissipated. It is the energy
dissipation in a component that causes the damage.
For this discussion we are assuming a protection circuit of the form as shown
below.
The first step is to calculate the amount of energy the interface needs to deal
with. Power (in Watts) dissipated is Energy per unit time:
In purely electrical terms it is also current x voltage:
Hence:
Using Ohms law
The equation can be re-written as:
The reason for writing like this is that R is a constant for the circuit and the
voltage V will vary with time. This will become clearer later.
Circuit to be
protected
External
High pulse
rated resistor
Uni (or bi) TVS
Uni (or bi) TVS
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For the sake of this discussion let’s assume we can employ a resistor of say 100Ω,
and still maintain all signal transition specifications.
From equation 1 it is clear that the series resistance must be known before the
energy can be calculated. With this in mind let’s find out the energy associated
with a double exponential pulse. There are two ways to do this. An accurate
method is employed by Vishay, the well-known manufacturer of thick film
resistors and TVS devices. The equation is given here:
Where:
is time to peak voltage (S)
is time to decay to half peak voltage (S)
is time the decay becomes negligible (nominally set to ) (S)
is the exponential rate of decay = - (S)
is the total series resistance in Ohms. Note that this is the pulse generator
output resistance plus the UUT series protection resistor.
Running through the calculation with a peak voltage of 300V and a protection
resistor R = 100Ω (Hence total series resistance of 100Ω + 5 Ω = 105Ω) gives
an energy of 0.04053 Joules. However note the following:
The above equation can give a rather large value due to the elongated tail of the
decaying exponential. In the example above a of 20 x the value is used. If a
larger multiplication factor is used such a calculation can give the impression
that a particular semiconductor device is specified to withstand the energy of a
DO160G 6.4/69 s pulse, but this is very much dependent on the calculation
made. A design engineer needs to take care to use reasonable margin in the
design to take care of component tolerances and to err very much on the side of
caution. For simplicity we can try using a far simpler model of that pulse. The
model I advocate is to treat the pulse as a simple triangular wave-shape.
To calculate the energy of any arbitrary wave-shape varying with time equation 1
can be re-written in calculus form as:
Where:
is time to decay to half peak voltage (S). We have used 2 x for our triangle
model.
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is now the time varying voltage, in this case a straight line from the peak
voltage at time = 0 to 0V at time =
Running through the derivation gives the following equation for the energy:
Details are given in appendix B.
The calculation with R=100Ω now gives a total energy of 0.0394 Joules.
Incidentally, using equation 2 to calculate the energy of a DO-160G Sine wave at
level 3, i.e. a peak of 600V (A single Sine wave peak) with the example of 100Ω
gives an energy of 0.0017 Joules. (23 times less than the double exponential just
looked at). See appendix B for the derivation. The Sine wave is of course
repeated at frequency so it is not entirely safe to assume it will not cause
damage to a UUT if the double exponential pulse does not. Furthermore the
higher voltage could damage an interface from a purely insulation strength point
of view.
Given the energy, it is now a matter of finding a suitable resistors and TVS.
To summarize, we have said that a 100Ω resistor can be used. We have assumed
that we wish to protect against a DO-160G level 3 lightning pulse. That means
protecting against a 6.4/69 s pulse. The testing will need to test against this
pulse for both voltage and current and for both positive and negative pulses.
Furthermore we have said that we need to mitigate against an energy of 0.0394
Joules.
Let’s now take our example a little further. Let’s assume that our interface is a
simple 12V logic level interface with low at 0V and high at 12V. Furthermore let’s
assume the interface can withstand an overvoltage up to 20V.
Let’s take the Littelfuse TVS as a candidate protection TVS. The SMAJ12A looks
like a good candidate device. It has the following features:
12V reverse stand-off voltage. This is the maximum voltage that does not put
the diode into an avalanche breakdown mode. Although some current may be
drawn.
13.3V minimum breakdown voltage. This is when the diode starts going into
breakdown.
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14.7V maximum breakdown voltage. This is the voltage at which the diode will
definitely (if not before) be in breakdown.
19.9V maximum clamping voltage. This is the voltage across the diode at
maximum current.
Since we don’t really want any conduction (and so no power loss) at normal
operating voltage of 12V and we don’t want any voltage greater than maximum
20V at the device to be protected, this diode would seem to be acceptable.
So we now need to look at its ability to cope with the 0.0394 Joules of energy.
We can now work out that, with a 6.4/69 s pulse (square pulse model) the TVS
is capable of mitigating an energy of 0.0829 Joules, so is acceptable. The
calculation goes as follows:
Firstly we note that the TVS will clamp at a voltage maximum of 19.9V. This is far
lower than the transient pulse we are considering and so it is reasonable (i.e.
worst case) to model the clamped signal as shown here:
As such we will model it as a simple square pulse. See appendix B, where the
energy is given as:
t
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So
Hence, in our example .
Since 0.0394 J < 0.0829 J, this TVS would seem to be ok.
Furthermore we can check on the Littelfuse data sheet by looking at the Peak
Pulse Power rating chart. Reading on the horizontal axis it shows that a pulse of
0.1ms (100s) means it can withstand a double exponential pulse with a peak
pulse power of some 1.8kW.
Our incident pulse has peak power of:
So again it will be ok. Note it is important when looking at such charts on
manufacturers’ data sheets to understand the pulse shape used. Some data
sheets use square wave pulses.
Further, note the data sheet shows a maximum peak pulse current of 20.1A. Our
peak current will be 19.9V / 105Ω = 0.198A, so also acceptable.
d. Is the TVS to be a unidirectional one or a bidirectional one?
This depends on two main signal parameters:
oIs the normal signal level only positive or positive and negative?
oIs the frequency of the signal such that capacitance is of utmost importance?
If the signal is a slow positive one then a uni-directional TVS is likely the best
option since this will clip any unwanted signals more closely to the required
signal range. However if capacitance is important then the bi-directional TVS has
slightly lower capacitance and so would be fine provided any small negative
pulse would not harm the UUT.
The unidirectional TVS will clip to the reverse stand-off voltage both negative
and positive. The uni-directional one will clip to the positive reverse stand-off
voltage and to the forward diode drop for negative signals.
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