VSH144Z (Z-Foil)
Vishay Foil Resistors
Ultra High Precision Z-Bulk Metal
®
Foil Technology Low Profile Conformally Coated
Voltage Divider Resistor with TCR Tracking to 0.1 ppm/°C, Power Coefficient
Tracking of 5 ppm at Rated Power, and Tolerance Match to 0.01 % (100 ppm)
FEATURES
Temperature coefficient of resistance (TCR):
absolute: ± 0.05 ppm/°C typical (0 °C to + 60 °C)
± 0.2 ppm/°C typical (- 55 °C to + 125 °C,
+ 25 °C ref.)
tracking: 0.1 ppm/°C typical
Tolerance: absolute and matching to 0.01 % (100 ppm)
Power coefficient tracking “R due to self heating”: 5 ppm
at rated power
Power rating: 0.2 W at 70 °C, for the entire resistive
element R
1
and R
2
, divided proportionally between the two
values
Load life ratio stability: < 0.01 % (100 ppm) 0.2 W at 70 °C
for 2000 h
V
out
VSH144Z
APPLICATIONS
Instrumentation amplifiers
Bridge networks
Differential amplifiers
Military
Space
Medical
Automatic test equipment
Down-hole (high temperature)
V
in
R
1
-
+
R
2
Maximum working voltage: 200 V
Resistance range: 100R to 20K per resistive element
Vishay Foil resistors are not restricted to standard
values/ratios; specific “as requested” values/ratios can be
supplied at no extra cost or delivery (e.g. 1K2345 vs. 1K)
Electrostatic discharge (ESD) up to 25 000 V
Non-inductive, non-capacitive design
Rise time: 1 ns effectively no ringing
Current noise: 0.010 µV
RMS
/V of applied voltage (< - 40 dB)
Thermal EMF: 0.05 µV/°C typical
Voltage coefficient: < 0.1 ppm/V
Non-inductive: < 0.08 µH
Non hot spot design
Thermal stabilization time < 1 s (nominal value achieved
within 10 ppm of steady state value)
Terminal finish: lead (Pb)-free or tin/lead alloy
Compliant to RoHS directive 2002/95/EC
Prototype quantities available in just 5 working days
or sooner. For more information, please contact
foil@vishaypg.com
For better performances please contact us
TABLE 1A - MODEL VSH144Z
SPECIFICATIONS
RESISTANCE
VALUES
500
to 20 k
100
to < 500
ABSOLUTE
TOLERANCE
± 0.01 %
± 0.02 %
ABSOLUTE TCR
(- 55 °C to + 125 °C, + 25 °C ref.)
TYPICAL AND MAX. SPREAD
± 0.2 ppm/°C ± 2.5 ppm/°C
TABLE 1B - MODEL VSH144Z
SPECIFICATIONS
RESISTANCE
RATIO
1:1
> 1:1 to 4:1
> 4:1 to 10:1
> 10:1
TOLERANCE
MATCH
0.01 %
TCR TRACKING MAX.
0.5 ppm/°C
0.75 ppm/°C
1.5 ppm/°C
2.0 ppm/°C
0.02 %
* Pb containing terminations are not RoHS compliant, exemptions may apply
Document Number: 63173
Revision: 29-Mar-10
For any questions, contact:
foil@vishaypg.com
www.foilresistors.com
1
VSH144Z (Z-Foil)
Vishay Foil Resistors
INTRODUCTION
The VSH144Z voltage divider is based on the latest
generation of Bulk Metal
®
Z-Foil technology which is the
most recommended solution for ultra high precision, stability
and reliable voltage division or anywhere else that requires
two resistors to maintain a stable ratio under power and
throughout all application variables.
Why are extremely low TCR resistors required?
This is a proper question when evaluating system cost. The
answers are as numerous as the system in which they are
installed but a few examples may provide insight:
1) Commercial broadcast equipment heats up through the
day and requires constant manual adjustment through the
day for proper signal adjustment.
2) Satellites in synchronous orbit rotate through temperature
extremes.
3) A fighter jet resting on the 115° desert floor takes off and
reaches altitude at - 60° in less than two minutes.
4) A system that requires fast response time in order to
produce the required signal with minimum stabilization
time.
Resistors may be selected for TCR tracking but that is
only useful when the resistors are operating at the same
temperature. If the resistors are operating at different
temperatures because of differential self-heating, or due
to locally-different thermal influence from different
adjacent components, or because they are operating in
different regions of the equipment, the ratios change
proportional to the differences in operating temperature
times and the absolute TCR in addition to differences in
TCR tracking ratios. Additionally, when resistors within a
set have different absolute TCR’s (individual TCR’s - not
relative or tracking TCR), the ratios change even more
due to the differential self-heating as well as to differential
ambient temperatures:
ratio = (TCR track x
temp 1) + (absolute TCR x
temp 2)
where
temp 1 is the change of ambient temperature
and
temp 2 is the temperature difference between two
resistors due to differential self-heating.
Differential self-heating can occur, for example, when the
same current flows through resistors of different
resistance values. The construction of the VSH144Z
keeps both resistors at the same temperature regardless
of resistance value or differential power.
For best performance in such applications, low absolute
TCRs are required.
What is TCR tracking and why it is important?
TCR tracking is a measure of the uniformity of the
thermally-induced resistance changes in two or more
resistors. Resistors “track” closely when their individual
TCRs are close, and this is a measure of how closely these
resistors will maintain their initial ratios over various
temperature changes. Some resistors may increase in value
with an increase in temperature (positive TCR) while others
will decrease in value with an increase in temperature
(negative TCR), or, they may not change in value at the
same rate (differential TCR). Other temperature effects, such
as self heating due to the application of power can add to the
ambient temperature effects. An example of these effects
can be seen where two resistors with different TCR
characteristics are used around an operation amplifier. The
amplification ratio will be affected by the differential TCR of
the resistors and will be compounded by the differential self
heating effects of the I
2
R differences of the feedback VS the
input resistor.
Good design practice requires fundamentally low TCR
networks in this application since this would minimize both
varying temperature and self heating effects.
This could not be accomplished with high TCR resistors,
even with good tracking.
What is the reason for such excellent stability?
The secret of Bulk Metal Z-Foil technology’s benchmark
stability lies in the fact that it retains the inherent metallurgical
stability of the alloy from which it is made: the alloy is not
melted and drawn as it is in the manufacture of wirewound
resistors, nor is it evaporated and re-deposited or sputtered
as it is in thin-film resistors. This underlying metallurgical
stability is preserved throughout the manufacturing
processes by preventing the introduction of additional
stresses into the final component.
Our application engineering department is available to
advise and make recommendations. For non-standard
technical requirements and special applications. Please
contact
foil@vishaypg.com.
www.foilresistors.com
2
For any questions, contact:
foil@vishaypg.com
Document Number: 63173
Revision: 29-Mar-10
VSH144Z (Z-Foil)
Vishay Foil Resistors
FIGURE 1 - TRIMMING TO VALUES
(conceptual illustration)
Interloop
Capacitance
Reduction
in Series
Mutual
Inductance
Reduction due
to Opposing
Current in
Adjacent Lines
Current Path
Before Trimming
Current Path
After Trimming
Trimming Process
Removes this Material
from Shorting Strip Area
Changing Current Path
and Increasing Resistance
Note:
Foil shown in
black,
etched spaces in
white
FIGURE 2 - STANDARD PRINTING AND DIMENSIONS
in inches (millimeters)
Model VSH144Z and Schematic
(2)
0.263 ± 0.02
(6.7 ± 0.5)
(3)
0.098 + 0.008/- 0.01
(2.5 + 0.2/- 0.3)
(3)
VSH
144Z T
1.0 (25.4)
Min.
0.100
(2.54)
0.200
(5.08)
(D.C.) -
1K/1K
0.283 ± 0.04
(7.2 ± 1.0)
R
1
R
2
1
2
3
Dimensional Tolerance: ± 0.010" (0.25)
(1)
(2)
(3)
Lead wires: #22 AWG solder coated copper,
0.75" minimum length
Each divider pair consists of two resistors on one
single chip
For lead (Pb)-free: print “T” after 144Z and “-” after (D.C.)
FIGURE 3 - POWER DERATING CURVE
FIGURE 4 - TYPICAL RESISTANCE/
TEMPERATURE CURVE
(for more details see table 1A)
TCR Chord Slopes for Different Temperature Ranges
+ 500
Percent of Rated Power at + 70 °C
100
%
- 55 °C
+ 70 °C
Rated Power
75
%
+ 400
+ 300
50
%
Recommended
operation for
< 150 ppm
ΔR
after 2000 h
load life
+ 200
+ 100
ΔR
0
R
(ppm)
- 100
- 200
- 300
- 400
0.05 ppm/°C
- 0.1 ppm/°C
- 0.16 ppm/°C
- 55
- 25
0
+ 25
0.1 ppm/°C
0.14 ppm/°C
0.2 ppm/°C
+ 60 + 75
+ 100 + 125
25
%
0
- 75
- 50
- 25
0
+ 25 + 50 + 75 + 100 + 125 + 150 + 175
- 500
Ambient Temperature (°C)
Ambient Temperature (°C)
Note:
• Power is divided proportionally between the 2 values
Document Number: 63173
Revision: 29-Mar-10
For any questions, contact:
foil@vishaypg.com
www.foilresistors.com
3
Embedded System
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