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VRE202 VRE202
DESCRIPTION
Precision Voltage Reference
FEaTuRES
Very High Accuracy: +2.5 V Output, 200 V Extremely Low Drift: 0.6 ppm/C (25C to +85C) Low Warm-up Drift: 1 ppm Typical Excellent Stability: 6 ppm/1000 Hrs. Typical Excellent Line Regulation: 6 ppm/V Typical Hermetic 20-Terminal Ceramic LCC Military Processing Option
VRE202 Series Precision Voltage References provide ultrastable +2.5 V outputs with 200 V 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. Significant improvements have been made in other performance parameters as well, including initial accuracy, warmup drift, line regulation, and longterm stability, making the VRE202 series the most accurate and stable 2.5 V surface mount references available. VRE202 devices are available in two operating temperature ranges, -25C to +85C and -55C to +125C, and two electrical performance grades. All devices are packaged in 20-terminal ceramic LCC packages for maximum long-term stability. "M" versions are screened for high reliability and quality.
aPPlICaTIONS

Precision A/D and D/A Converters Transducer Excitation Accurate Comparator Threshold Reference High Resolution Servo Systems Digital Voltmeters High Precision Test and Measurement Instruments
Figure 1. BlOCK DIaGRaM
11
SElECTION GuIDE
Model VRE202C VRE202CA VRE202M VRE202MA Output (V) +2.5V +2.5V +2.5V +2.5V Temperature Operating Range -25C to +85C -25C to +85C -55C to +125C -55C to +125C Volt Deviation (MaX) 200V 100V 400V 200V
20-terminal Ceramic lCC Package Style HD Jul 2009 1 APEX - VRE202DSREVH
VRE202DS
http://www.cirrus.com
Copyright (c) Cirrus Logic, Inc. 2009 (All Rights Reserved)
VRE202
P r o d u c t I n n o v a t i o nF r o m
1. CHARACtERiStiCS AnD SPECifiCAtionS ElECTRICal SPECIFICaTIONS
VPS =+15V, T = +25C, RL = 10K UnLESS OTHERWISE nOTED.
Grade Parameter Power Supply Operating Temperature Storage Temperature Short Circuit Protection OuTPuT VOlTaGE VRE202 OuTPuT VOlTaGE ERRORS Initial Error Warmup Drift TMIn - TMAX (note1) 6 1.5 10 6 3 10 4 5 5 7 7 10 * * * * * * * * * * Long-Term Stability noise (0.1 - 10Hz) OuTPuT CuRRENT Range REGulaTION Line Load OuTPuT aDJuSTMENT Range Temperature Coefficient POWER SuPPlY CuRRENT (note 2) VRE202 +PS VRE202 -PS mA mA mV V/C/mV ppm/V ppm/mA mA 2 200 * * 300 1 100 200 V ppm V ppm/1000hrs. Vpp +2.5 * V Min +13.5 -25 -65 Continuous aBSOluTE MaXIMuM RaTINGS +22 +85 +150 * * * * * * * V C C C Typ Max Min Ca Typ Max units
nOTES:
* Same as C Models. 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.
2
VRE202DS
P r o d u c t I n n o v a t i o nF r o m
VRE202
2. TYPICal PERFORMaNCE CuRVES
VOUT vs. TEMPERATURE VOUT vs. TEMPERATURE
Temperature oC VRE202C VOUT vs. TEMPERATURE
Temperature oC VRE202CA VOUT vs. TEMPERATURE
Temperature oC VRE202M
Temperature oC VRE202MA
QUIESCENT CURRENT VS. TEMP
JUNCTION TEMP. RISE VS. OUTPUT CURRENT
PSRR VS. FREQUENCY
Temperature oC
Output Current (mA)
Frequency (Hz)
VRE202DS
3
VRE202
3. tHEoRY of oPERA tion
P r o d u c t I n n o v a t i o nF r o m
The following discussion refers to the block diagram in Figure 1. A FET current source is used to bias a 6.3 V 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 2.5 V output. The gain is determined by the resistor networks R3 and R4: G=1 + R4/R3. The 6.3 V 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 references' 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 compensation technique is not well suited for wide temperature ranges. A nonlinear compensation network of thermistors and resistors is used in the VRE series voltage references. this proprietary network eliminates most of the nonlinearity in the voltage vs. temperature function. Then by adjusting the slope, a very stable voltage over wide temperature ranges is produced. This network is less than 2% of the overall network resistance so it has a negligible effect on long term stability. By using highly stable resistors in our network, a voltage reference is produced that also has very good long term stability.
4. aPPlICaTION INFORMaTION
The proper connection of the VRE202 series voltage references with the optional trim resistors is shown below. Pay careful attention to the circuit layout to avoid noise pickup and voltage drops in the lines. The VRE202 series voltage references have the ground terminal brought out on two pins (pin 9 and pin 10) 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 20 ppm. By connecting pin 10 to the power supply ground and pin 9 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 does not effect performance.
EXTERNal CONNECTIONS
-15V
2 3 4 1 20 19 18 17 16 15 9 10 11 12 13 14
PIN CONFIGuRaTION
NC NC NC VOUT NC
18 17 16 15 14
NC 19 NC 20 NC
13 NC
+15V
5 6 7 8
1 2 3
VRE202
TOP VIEW
12 NC 11 TRIM 10 GND 9
REF GND
VOUT = +2.5V
NC NC
4 5 6 7 8
NC VIN NC NC NC
Ref. Gnd.
10K
4
VRE202DS

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