VRE117/118/119
Precision
Reference Supplies
THALER CORPORATION • 2015 N. FORBES BOULEVARD • TUCSON, AZ. 85745 • (520) 882-4000
FEATURES
•
VERY HIGH ACCURACY: 3.000 V OUTPUT ±200 µV
•
EXTREMELY LOW DRIFT: 0.6 ppm/°C 55°C to +125°C
•
LOW WARM-UP DRIFT: 1 ppm Typ.
•
EXCELLENT STABILITY: 6 ppm/1000 Hrs. Typ.
APPLICATIONS
•
PRECISION A/D and D/A CONVERTERS
•
TRANSDUCER EXCITATION
•
ACCURATE COMPARATOR THRESHOLD
REFERENCE
•
HIGH RESOLUTION SERVO SYSTEMS
•
EXCELLENT LINE REGULATION: 3 ppm/V Typ.
•
DIGITAL VOLTMETERS
•
HERMETIC 14-PIN CERAMIC DIP
•
MILITARY PROCESSING OPTION
•
HIGH PRECISION TEST and
MEASUREMENT INSTRUMENTS
DESCRIPTION
VRE117 Series Precision Voltage References
provide ultrastable +3.000V (VRE117), -3.000V
(VRE118) and ±3.000V (VRE119) outputs with
±0.200 mV initial accuracy and temperature
coefficient as low as 0.6 ppm/°C over the full
military temperature range. This improvement in
accuracy is made possible by a unique,
proprietary
multipoint
laser
compensation
technique developed by Thaler Corporation.
Significant improvements have been made in
other performance parameters as well, including
initial accuracy, warm-up drift, line regulation, and
long-term stability, making the VRE117 series the
most accurate and stable 3.0V reference
available.
SELECTION GUIDE
Type
VRE117C
VRE117CA
VRE117M
VRE117MA
VRE118C
VRE118CA
VRE118M
VRE118MA
VRE119C
VRE119CA
VRE119M
VRE119MA
Output
+3.0V
+3.0V
+3.0V
+3.0V
-3.0V
-3.0V
-3.0V
-3.0V
±3.0V
±3.0V
±3.0V
±3.0V
Temperature
Operating Range
-25°C to +85°C
-25°C to +85°C
-55°C to +125°C
-55°C to +125°C
-25°C to +85°C
-25°C to +85°C
-55°C to +125°C
-55°C to +125°C
-25°C to +85°C
-25°C to +85°C
-55°C to +125°C
-55°C to +125°C
Max. Volt
Deviation
200 µV
100 µV
400 µV
200 µV
200 µV
100 µV
400 µV
200 µV
200 µV
100 µV
400 µV
200 µV
VRE117/118/119 devices are available in two
operating temperature ranges, -25°C to +85°C
and -55°C to +125°C, and two performance
grades. All devices are packaged in 14-pin hermetic ceramic packages for maximum long-term stability. "M"
versions are screened for high reliability and quality.
Superior stability, accuracy, and quality make these references ideal for precision applications such as A/D
and D/A converters, high-accuracy test and measurement instrumentation, and transducer excitation.
VRE117DS REV. C NOV 2000
DISCUSSION OF PERFORMANCE
THEORY OF OPERATION
The following discussion refers to the schematic
below. A FET current source is used to bias a 6.3V
zener diode. The zener voltage is divided by the
resistor network R1 and R2. This voltage is then
applied to the noninverting input of the operational
amplifier which amplifies the voltage to produce a
3.000V output. The gain is determined by the
resistor networks R3 and R4: G=1 + R4/R3. The
6.3V zener diode is used because it is the most
stable diode over time and temperature.
The current source provides a closely regulated
zener current, which determines the slope of the
reference's voltage vs. temperature function. By
trimming the zener current, a lower drift over
temperature can be achieved. But since the voltage
vs. temperature function is nonlinear, this method
leaves a residual error over wide temperature
ranges.
To remove this residual error, Thaler Corporation
has developed a nonlinear compensation network of
thermistors and resistors that is used in the VRE117
series references. This proprietary network
eliminates most of the nonlinearity in the voltage vs.
temperature function. By then adjusting the slope,
Thaler Corporation produces a very stable voltage
over wide temperature ranges. This network is less
than 2% of the overall network resistance so it has a
negligible effect on long term stability.
APPLICATION INFORMATION
Figure 1 shows the proper connection of the
VRE117 series voltage reference with the optional
trim resistors. When trimming the VRE119, the
positive voltage should be trimmed first since the
negative voltage tracks the positive side. Pay careful
attention to the circuit layout to avoid noise pickup
and voltage drops in the lines.
The VRE117 series voltage references have the
ground terminal brought out on two pins (pin 6 and
pin 7) which are connected together internally. This
allows the user to achieve greater accuracy when
using a socket. Voltage references have a voltage
drop across their power supply ground pin due to
quiescent current flowing through the contact
resistance. If the contact resistance was constant with
time and temperature, this voltage drop could be
trimmed out. When the reference is plugged into a
socket, this source of error can be as high as 20ppm.
By connecting pin 7 to the power supply ground and
pin 6 to a high impedance ground point in the
measurement circuit, the error due to the contact
resistance can be eliminated. If the unit is soldered
into place the contact resistance is sufficiently small
that it doesn't effect performance.
VRE117
VRE119
VRE117DS REV. C NOV 2000
Analog electronics
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