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P r o VRE202 a t i o n F r o m duct Innov
VRE202 VRE202
DESCRIPTION
Precision Voltage Reference
FEATURES
Very High Accuracy: +2.5 V Output, 300 V Extremely Low Drift: 0.73 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 300 V initial accuracy and temperature coefficient as low as 0.73 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
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SELECTION GUIDE
Model VRE202C VRE202CA Output (V) +2.5V +2.5V Temperature Operating Range -25C to +85C -25C to +85C Volt Deviation (MAX) 250V 200V
20-terminal Ceramic LCC Package Style HD
VRE202DS
Copyright (c) Cirrus Logic, Inc. 2009 (All Rights Reserved)
www.cirrus.com
NOV 2009 1 APEX - VRE202DSREVI
VRE202
Product Innovation From
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 2 250 * * 350 1 200 300 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.
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VRE202DS
Product Innovation From
VRE202
2. TYPICAL PERFORMANCE CURVES
VOUT vs. TEMPERATURE VOUT vs. TEMPERATURE
0.25 -0.25
0.2 -0.2
Temperature oC VRE202C
QUIESCENT CURRENT VS. TEMP
Temperature oC VRE202CA
JUNCTION TEMP. RISE VS. OUTPUT CURRENT PSRR VS. FREQUENCY
Temperature oC
Output Current (mA)
Frequency (Hz)
3. THEORY OF OPERATION
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.
VRE202DS
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VRE202
4. APPLICATION INFORMATION
Product Innovation From
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
3 4 2 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
CONTACTING CIRRUS LOGIC SUPPORT
For all Apex Precision Power product questions and inquiries, call toll free 800-546-2739 in North America. For inquiries via email, please contact apex.support@cirrus.com. International customers can also request support by contacting their local Cirrus Logic Sales Representative. To find the one nearest to you, go to www.cirrus.com
IMPORTANT NOTICE Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject to change without notice and is provided "AS IS" without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, indemnification, and limitation of liability. No responsibility is assumed by Cirrus for the use of this information, including use of this information as the basis for manufacture or sale of any items, or for infringement of patents or other rights of third parties. This document is the property of Cirrus and by furnishing this information, Cirrus grants no license, express or implied under any patents, mask work rights, copyrights, trademarks, trade secrets or other intellectual property rights. Cirrus owns the copyrights associated with the information contained herein and gives consent for copies to be made of the information only for use within your organization with respect to Cirrus integrated circuits or other products of Cirrus. This consent does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale. CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE ("CRITICAL APPLICATIONS"). CIRRUS PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED TO BE SUITABLE FOR USE IN PRODUCTS SURGICALLY IMPLANTED INTO THE BODY, AUTOMOTIVE SAFETY OR SECURITY DEVICES, LIFE SUPPORT PRODUCTS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF CIRRUS PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE FULLY AT THE CUSTOMER'S RISK AND CIRRUS DISCLAIMS AND MAKES NO WARRANTY, EXPRESS, STATUTORY OR IMPLIED, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR PARTICULAR PURPOSE, WITH REGARD TO ANY CIRRUS PRODUCT THAT IS USED IN SUCH A MANNER. IF THE CUSTOMER OR CUSTOMER'S CUSTOMER USES OR PERMITS THE USE OF CIRRUS PRODUCTS IN CRITICAL APPLICATIONS, CUSTOMER AGREES, BY SUCH USE, TO FULLY INDEMNIFY CIRRUS, ITS OFFICERS, DIRECTORS, EMPLOYEES, DISTRIBUTORS AND OTHER AGENTS FROM ANY AND ALL LIABILITY, INCLUDING ATTORNEYS' FEES AND COSTS, THAT MAY RESULT FROM OR ARISE IN CONNECTION WITH THESE USES. Cirrus Logic, Cirrus, and the Cirrus Logic logo designs, Apex Precision Power, Apex and the Apex Precision Power logo designs are trademarks of Cirrus Logic, Inc. All other brand and product names in this document may be trademarks or service marks of their respective owners.
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VRE202DS

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