PWC1205 [ETC]
Pulse Withstanding Chip Resistors; 耐脉冲片式电阻器
| 型号： | PWC1205 |
| 厂家： | 
ETC |
| 描述： | Pulse Withstanding Chip Resistors |
| 文件： | 总6页 (文件大小：271K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Resistive Components
Pulse Withstanding
Chip Resistors
PWC Series
• Excellent pulse
Today’s electronic devices are becoming
smaller and smaller. As a result designers
are moving more towards surface mount
components not only for new designs
but also to design out large axial and
other through-hole resistors. In most
cases this is a straightforward task as
several resistor manufacturers offer chip
resistors with performances to match
axial parts. However in some cases, due
to power rating or pulse withstanding
requirements, this has been impossible.
The requirement, in particular, for pulse
withstand capability is growing due to
the need to protect sensitive modern
electronic systems.
To meet this demand TT electronics have
handling
designed a Pulse Withstanding Chip
performance
Resistor (PWC Series). The PWC series is
available in four standard sizes from
0805 to 2512 as shown in the following
table. The table also gives details of the
improved LEV (Limiting Element Voltage)
and increased power rating. Pulse
withstanding details are given on the
following pages.
• Cost effective
custom designs
available
• Field proven with
millions of units
in use
The enhanced performance of the chips
is made possible by the precise use of
the best resistance inks and a closely
controlled production process.
• Standard and
custom chip sizes
(0805 to 2512)
Subsidiaries of TT electronics plc
Leading in Tomorrow’s Technology
2
Size
0805
1206
2010
2512
Power @70°C
0.125W
0.33W
0.75W
1.5W
Resistance range
1R0 to 10M
Tolerance
0.5*, 1, 2, 5%
LEV
150V
200V
400V
500V
TCR
<10R:200ppm/°C ≥10R:100ppm/°C
-55 to +155°C
Operating temperature
Values
E96 preferred other values to special order
See following pages
Pulse capability
*0.5% Tolerance only available on values 10R to 1MO.
Applications
Applications vary from line protection for telecommunications
to surge withstanding resistors for use in circuit breakers.
Details of a typical telecomm and power supply application are
given below.
Protection in the system and the resistors are required to
withstand pulses of 15 Watts for 1 second and 75 Watts for
0.1 second, repeated 60 times. Test requirements for telecomms
applications are laid down by the International
Telecommunications Union (ITU) and Bell Communications
Research (Bellcore).
Telephone lines can be subjected to a large range of voltage
disturbances, many of which can damage switching equipment.
This has led to the need for circuit protection against both high
voltage transients, usually of short duration caused by lighting
strikes and overloads of longer duration, due to direct
connection to mains power lines.
Fig 2 shows a typical power supply or battery charger circuit. In
this application the resistor is required to withstand a small
inrush surge, and also a lightning strike surge. The lightning
strike is usually simulated by applying either a 1.2/50µs or
10/700µs pulse shape, the number of pulses and pulse intervals
being specified by the customer or the relevant standard. Typical
standards to be met are Cenelec EN50082-1 and EN50082-2
which are part of the European EMC directives, and
These two faults are separated into primary and secondary
protection. Primary protection handles the high voltage
transients, and is usually located within the exchange. Secondary
protection is usually built into the equipment to be protected,
and deals with both current and voltage limiting.
Bellcore 1089 for the US market.
To determine the suitability of a PWC series chip resistors for
your application refer to the pulse withstanding data as given
below. Graphs have been produced to show the PWC
performance under single and continuous pulse, maximum pulse
voltage for single and continuous pulses and lighting surge
performance using both 1.2/50µs and 10/700µs pulse shapes.
Voltage limiting prevents damage to the equipment and shock
hazards, and current limiting prevents damage to wiring.
A typical application circuit is shown in fig 1 where the resistors
are designed for ring signal sending through a solid state relay.
The resistors are protected from lightning surge by Over-voltage
Welwyn
Resistor
Lightning Surge
Over
Voltage
Line
Protection
Input
Power
Supply
Circuit
Output
Welwyn
Resistor
Fig 1
Fig 2
3
Description of Performance Tests
The formula used to calculate the average power for repetitive
pulses is shown below.
Single Impulse
The single impulse graph was the result of 50 impulses of
rectangular shape applied at one minute intervals. The limit of
acceptance was a shift in resistance of less than 1% from the
initial value. The power applied was subject to the restrictions
of the maximum permissible impulse voltage graph as shown.
V2 ti < Pnom
R tp
For a rectangular impulse
P =
V2 te < Pnom
R 2tp
For an exponential impulse P =
Continuous Load Due to
Repetitive Pulses
The continuous load graph was obtained by applying repetitive
rectangular pulses where the pulse period (tp) was adjusted so
that the average power dissipated in the resistor was equal to
its rated power at 70°C. Again the limit of acceptance was a
shift in resistance of less than 1% from the initial value.
Where
R
=
=
nominal resistance
tp
time of the pulse period
(1/tp = pulse frequency)
V
P
=
=
peak voltage of the impulse
average power dissipation
of continuous pulses
ti
=
=
impulse time of a rectangular pulse
time constant of an exponential pulse
Te
Rectangular Pulses
Exponential Pulse
4
Resistive Components
Single Pulse
1000
100
10
0805
1206
2010
2512
1
0.0001
0.001
0.01
0.1
1
Pulse Duration ti (s)
Continuous Pulses
100
10
1
0805
1206
2010
2512
0.1
0.0001
0.001
0.01
0.1
1
Pulse Duration ti (s)
Pulse Voltage
10000
1000
100
O805
1206
2010
2512
10
0.0001
0.001
0.01
0.1
1
Pulse Duration ti (s)
5
Resistive Components
Lightning Surge
Resistors are tested in accordance with IEC61000-4-5 using both 1.2/50µs and 10/700µs pulse shapes and Bellcore 1089 using both
2/10µs and 10/1000µs pulse shapes (2512 size only). The limit of acceptance is a shift in resistance of less than 1% from the initial value.
1.2/50µs Lightning Surge
10000
1000
0805
1206
2010
2512
100
10
1
10
100
1000
10000
100000
1000000
10000000
Value (ohms)
10/700µs Lightning Surge
10000
1000
100
0805
1206
2010
2512
10
1
10
100
1000
10000
100000
1000000
10000000
Value (ohms)
PWC2512 Pulse Testing to Bellcore 1089 Specification
10000
1000
100
10
10/1000µs
2/10µs
1
10
100
1000
10000
100000
1000000
10000000
Value (ohms)
6
Resistive Components
Performance Data
Maximum
Typical
0.25
Load at rated power: 1000 hours at 70°C
Shelf life: 12 months at room temperature
Derating from rated power at 70°C
Overload: 6.25 x rated power for 5 seconds
Dry heat: 1000 hours at 155°C
Long term damp heat
∆R%
∆R%
2
0.1
0.02
Zero at 155°C
∆R%
∆R%
∆R%
∆R%
∆R%
Volts
1
1
0.1
0.2
1
0.25
0.05
0.05
Temperature rapid change
0.25
0.25
Resistance to solder heat
Voltage proof
500
Note: An 0.01 ohm addition to be added to the performance of all resistors <10 ohms.
Physical Data
Dimensions of PWC chips are given below in mm and weight in g.
Wrap-around terminations
L
W
T max
0.6
A
B*
C
Wt.
(3 faces)
0805
1206
2010
2512
2.0 0.3
3.2 0.4
5.1 0.3
6.5 0.3
1.25 0.2
1.6 0.2
2.5 0.2
3.2 0.2
0.3 0.15
0.4 0.2
0.6 0.3
0.6 0.3
0.9 min
1.7 min
3.0 min
4.4 min
0.3 0.1
0.4 0.15
N/A
0.009
0.020
0.036
0.055
T
0.7
A
0.8
B
L
W
A
0.8
N/A
* This dimension determines the number of conductors which may pass under the surface mounted chip.
Construction & Solderability
Thick film resistor material, overglaze and organic protection
are screen printed on a 96% alumina substrate. Wrap-around
terminations have an electroplated nickel barrier and tin-lead
solder coating, this ensures excellent ‘leach’ resistance
properties and solderability. Chips can withstand immersion in
solder at 260°C for 30 seconds.
TT electronics has over 60 years experience in designing and manufacturing resistive components.
IRC Inc. (AFD)
4222 South Staples Street
Corpus Christi, Texas 78411, USA
Welwyn Components Limited
Welwyn Electronics Park, Bedlington
Northumberland NE22 7AA, UK
Telephone: +1 361 992 7900
Facsimile: +1 361 992 3377
Email: ircafd@irctt.com
Telephone: +44 (0) 1670 822181
Facsimile: +44 (0) 1670 829465
Email: info@welwyn-tt.com
Leading in Tomorrow’s Technology
Website: www.irctt.com
Website: www.welwyn-tt.com
General Note Welwyn Components / IRC reserves the right to make changes in product specification without notice or liability.
All information is subject to Welwyn’s / IRC’s own data and is considered accurate at time of going to print.
Subsidiaries of TT electronics plc
Issue B · 01.03
© Welwyn Components Limited
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