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VRE125/127
Precision High Temperature Reference Supplies
RHOPOINT COMPONENTS LTD., Holland Road,Hurst Green, Oxted, Surrey, RH8 0AX. Tel: +44 (0)1883 717988
FEATURES
* WIDE OPERATING RANGE: -55C to +200C * VERY HIGH ACCURACY: 5.000 V 0.4 mV * EXTREMELY LOW DRIFT: 0.6 mV (-55C to +150C) 2.0 mV (-55C to +200C) * EXCELLENT STABILITY: 6 ppm / 1000Hrs. * EXCELLENT LINE REGULATION: 6 ppm / V Typ. * HERMETIC 14-PIN DIP
APPLICATIONS
* PRECISION A/D and D/A CONVERTERS * ACCURATE COMPARATOR THRESHOLD VOLTAGE * HIGH RESOLUTION SERVO SYSTEMS * HIGH TEMPERATURE TEST and MEASUREMENT SYSTEMS * TRANSDUCER EXCITATION * GEOLOGICAL EQUIPMENT
DESCRIPTION
VRE125 series references are designed to operate over an extremely wide temperature range (-55C to +200C) and still provide excellent accuracy. The VRE125 provides a +5V output and the VRE127 provides a 5V output. All types are available in commercial (C suffix) and military (M suffix) models. They are hermetically sealed and are screened for high reliability and quality. Two accuracy grades (standard and A) are available in both models. The adjacent selector guide shows the limits of the most important parameters of the VRE125/127 series references. SELECTION GUIDE
Max. Volt Deviation (-55C to +150C) Max. Volt Deviation (150C to +200C) Initial Error (Max)
Type VRE125C VRE125CA VRE125M VRE125MA VRE127C VRE127CA VRE127M VRE127MA
Output +5V +5V +5V +5V 5V 5V 5V 5V
0.9mV 0.6mV 0.9mV 0.6mV 0.9mV 0.6mV 0.9mV 0.6mV
3.0mV 2.0mV 3.0mV 2.0mV 3.0mV 2.0mV 3.0mV 2.0mV
0.8mV 0.4mV 0.8mV 0.4mV 0.8mV 0.4mV 0.8mV 0.4mV
The accuracy of the VRE125/127 series over temperature is achieved by using Thaler Corporation's patented multi-point compensation technique. The stability of the VRE125 series is enhanced by using a zener diode instead of a bandgap reference, which is typically used in 5V references. Zener diodes have better long term stability and don't suffer the significant shifts caused by temperature cycling that bandgap references do. Other performance parameters, such as warm-up drift and long term stability are better than competitive models. Superior stability, accuracy, and quality make these references ideal for high temperature applications such as A/D and D/A converter references.
VRE125DS REV. C SEPT 1994
ELECTRICAL SPECIFICATIONS
Vps =15V, T = 25C, RL = 10K unless otherwise noted.
VRE125/127
CA
MIN TYP MAX MIN
MODEL PARAMETERS
MIN
C
TYP MAX
M
MA UNITS
TYP MAX MIN TYP MAX
ABSOLUTE MAXIMUM RATINGS Power Supply 13.5 22 Operating Temperature -55 200 Storage Temperature -65 150 Short Circuit Protection Continuous OUTPUT VOLTAGE VRE125 VRE127 +5 5 * * * * * * V V * * * * * * * * * * * * * * * * * * * * * V C C
OUTPUT VOLTAGE ERRORS Initial Error Warmup Drift (1) -55C to 150C (3) 150C to 200C Long-Term Stability Noise (.1-10Hz) OUTPUT CURRENT Range REGULATION Line Load OUTPUT ADJUSTMENT Range Temperature Coefficient POWER SUPPLY CURRENTS VRE125 +PS VRE127 +PS VRE127 -PS NOTES: *Same as C Models.
(2)
0.8 2 0.9 3.0 6 3 * * 1
0.4 2 0.6 2.0 * *
0.8 * * * *
0.4 1 * *
mV ppm mV mV ppm/1000hr. Vpp
10
*
*
*
mA
6 3
10
* *
*
* *
*
* *
*
ppm/V ppm/mA
10 4
* *
* *
* *
mV V/C/mV
4 6 4
7 9 6
* * *
* * *
* * *
* * *
* * *
* * *
mA mA mA
1.Using the box method, the specified value is the maximum deviation from the output voltage at 25C over the specified operating temperature range. 2.The specified values are unloaded. 3. Cone widening from 150 C value to specified value.
VRE125DS REV. C SEPT 1994
TYPICAL PERFORMANCE CURVES
VOUT vs. TEMPERATURE VOUT vs. TEMPERATURE VOUT vs. TEMPERATURE VOUT vs. TEMPERATURE
Temperature oC VRE125/127C
Temperature oC VRE125/127CA
Temperature oC VRE125/127M
Temperature oC VRE125/127MA
VRE125
QUIESCENT CURRENT VS. TEMP JUNCTION TEMP. RISE VS. OUTPUT CURRENT PSRR VS. FREQUENCY
Temperature oC
Output Current (mA)
Frequency (Hz)
VRE127
POSITIVE OUTPUT QUIESCENT CURRENT VS. TEMP JUNCTION TEMP. RISE VS. OUTPUT CURRENT PSRR VS. FREQUENCY
Temperature oC
Output Current (mA)
NEGATIVE OUTPUT
Frequency (Hz)
QUIESCENT CURRENT VS. TEMP
JUNCTION TEMP. RISE VS. OUTPUT CURRENT
PSRR VS. FREQUENCY
Temperature oC
Output Current (mA)
Frequency (Hz)
VRE125DS REV. C SEPT.1994
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 5.000V 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. tamperature 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 has developed a nonlinear compensation network of thermistors and resistors that is used in the VRE 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 VRE125 series voltage reference with the optional trim resistors. When trimming the VRE127, 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. When using precision voltage references at high temperatures it is best to keep them powered up. If the zener diode isn't powered up at high temperatures the junction will collect ions, and then when power is applied, the voltage will drift until the charge build up is depleted. The VRE125 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.
VRE125
FIGURE 2
VRE127
FIGURE 3
VRE125DS REV. C SEPT 1994
EXTERNAL CONNECTIONS
FIGURE 1 3. Optional Fine Adjust for approximately 10mV. VRE127 center tap connects to -PS. 4. Pin 6 is internally connected to Pin 7 and can be used as Ref. GND.
PIN CONFIGURATION
TOP VIEW
NC NC NC NC NC REF. GND GND FINE ADJ. +5V FINE ADJ. -ADJ. -5V -ADJ. -PS NC REF. GND GND
TOP VIEW
+ADJ. +5V +ADJ.
VRE125
+PS NC NC NC
VRE127
+PS NC NC NC
MECHANICAL
14-PIN HYBRID PACKAGE
INCHES DIM E L D B B1 B2 S P MIN .480 .195 .775 .016 .038 .095 .085 .004 MAX .500 .215 .805 .020 .042 .105 .105 .006 MILLIMETER MIN 12.1 4.9 19.7 0.4 0.9 2.4 2.1 0.10 MAX 12.7 5.4 20.4 0.5 1.0 2.6 2.6 0.15 DIM A Q Q1 C G1 INCHES MIN .120 .015 N/A .009 .290 MAX .155 .035 .030 .012 .310 MILLIMETER MIN MAX 3.0 0.4 N/A 0.2 7.3 4.0 0.9 0.7 0.3 7.8
VRE125DS REV. C SEPT 1994

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