VRE305 VRE305 VRE305 Precision Voltage Reference FEATURES +5 V Output, 0.5 mV (.01%) Temperature Drift: 0.6 ppm/C Low Noise: 3 VP-P (0.1-10Hz) Industry Standard Pinout: 8-pin DIP or Surface Mount Package Excellent Line Regulation: 6 ppm/V Typical Output Trim Capability APPLICATIONS The VRE305 is recommended for use as a reference for 14, 16, or 18 bit D/A converters which require an external precision reference. The device is also ideal for calibrating scale factor on high resolution A/D converters. The VRE305 offers superior performance over monolithic references. DESCRIPTION The VRE305 is a low cost, high precision +5 V reference. Packaged in an industry standard 8-pin DIP or SMT, the device is ideal for upgrading systems that use lower performance references. The device provides ultrastable +5 V output with 0.5 mV (.01%) initial accuracy and a temperature coefficient of 0.6 ppm/C. This improvement in accuracy is made possible by a unique, patented multipoint laser compensation technique. 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 VRE305 series the most accurate reference available in a standard 8-pin DIP or SMT. For enhanced performance, the VRE305 has an external trim option for users who want less than 0.01% initial error. For ultra low noise applications, an external capacitor can be attached between the noise reduction pin and the ground pin. A reference ground pin is provided to eliminate socket contact resistance errors. Figure 1. BLOCK DIAGRAM SELECTION GUIDE Model VRE305AS VRE305AD VRE305CS VRE305CD VRE305LS Initial Error Temp. Coeff. (mV) (ppm/C) 0.5 0.5 1.0 1.0 1.0 www.apexanalog.com VRE305DS 0.6 0.6 2.0 2.0 2.0 Temp. Range (C) Package Options 0C to +70C 0C to +70C 0C to +70C 0C to +70C -40C to +85C SIP8 (GD) DIP8 (KD) SIP8 (GD) DIP8 (KD) SIP8 (GD) 8-pin Surface Mount 8-pin DIP Package Style GD Package Style KD Copyright (c) Apex Microtechnology, Inc. 2012 (All Rights Reserved) SEP 2012 1 VRE305DS REVH VRE305 1. CHARACTERISTICS AND SPECIFICATIONS ELECTRICAL SPECIFICATIONS VPS = +15V, T = +25C, RL = 10K Unless Otherwise Noted. Model A Parameter C/L Min Typ Max Min Typ Max Units +13.5 +15 +22 * * * V +70 * * C +150 * * C ABSOLUTE MAXIMUM RATINGS Power Supply Operating Temperature 0 Storage Temperature -65 Short Circuit Protection Continuous * VRE305 +5.0 * V Temp. Sensor Voltage (Note 1) 630 * mV OUTPUT VOLTAGE OUTPUT VOLTAGE ERRORS Initial Error (Note 2) 0.5 Warmup Drift TMIN - TMAX 1 (Note3) 3 0.6 Long-Term Stability Noise (0.1 - 10Hz) 1.00 (Note 4) mV ppm 2.0 ppm/C 6 * ppm/1000hrs. 3 * Vpp OUTPUT CURRENT Range 10 mA REGULATION Line 6 10 * * ppm/V Load 3 * ppm/mA 10 * mV OUTPUT ADJUSTMENT Range POWER SUPPLY CURRENT (Note 5) VRE305 +PS 5 7 * * mA NOTES: * Same as A Model. 1. The temp. reference TC is 2.1 mV/ C 2. The specified values are without external trim. 3. The temperature coefficient is determined by the box method using the following formula: VMAX - VMIN T.C. = x 106 VNOMINAL x (TMAX - TMIN) 4. The specified values are without the external noise reduction capacitor. 5. The specified values are unloaded. 2 VRE305DS VRE305 2. TYPICAL PERFORMANCE CURVES VOUT vs. TEMPERATURE Temperature oC VRE305A QUIESCENT CURRENT VS. TEMP Temperature oC VOUT vs. TEMPERATURE Temperature oC VRE305C JUNCTION TEMP. RISE VS. OUTPUT CURRENT Output Current (mA) VOUT vs. TEMPERATURE Temperature oC VRE305L PSRR VS. FREQUENCY 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 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. By adjusting the slope, a very stable voltage is produced 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. VRE305DS 3 VRE305 The proper connection of the VRE305 series voltage references with the optional trim resistor for initial error and the optional capacitor for noise reduction is shown below. The VRE305 reference has the ground terminal brought out on two pins (pin 4 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 20 ppm. By connecting pin 4 to the power supply ground and pin 7 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. Pay careful attention to the circuit layout to avoid noise pickup and voltage drops in the lines. EXTERNAL CONNECTIONS + VIN 2 OPTIONAL NOISE REDUCTION CAPACITOR CN 1F 3 8 6 VRE305 5 7 PIN CONFIGURATION V TEMP OUT 4 + VOUT 10K OPTIONAL FINE TRIM ADJUSTMENT N/C 1 +VIN 2 TEMP 3 GND 4 VRE305 TOP VIEW 8 NOISE REDUCTION 7 REF. GND 6 VOUT 5 TRIM REF. GND NEED TECHNICAL HELP? CONTACT APEX SUPPORT! For all Apex Microtechnology product questions and inquiries, call toll free 800-546-2739 in North America. For inquiries via email, please contact apex.support@apexanalog.com. International customers can also request support by contacting their local Apex Microtechnology Sales Representative. To find the one nearest to you, go to www.apexanalog.com IMPORTANT NOTICE Apex Microtechnology, Inc. has made every effort to insure the accuracy of the content contained in this document. However, the information is subject to change without notice and is provided "AS IS" without warranty of any kind (expressed or implied). Apex Microtechnology reserves the right to make changes without further notice to any specifications or products mentioned herein to improve reliability. This document is the property of Apex Microtechnology and by furnishing this information, Apex Microtechnology grants no license, expressed or implied under any patents, mask work rights, copyrights, trademarks, trade secrets or other intellectual property rights. Apex Microtechnology 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 Apex Microtechnology integrated circuits or other products of Apex Microtechnology. 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. APEX MICROTECHNOLOGY PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED TO BE SUITABLE FOR USE IN PRODUCTS USED FOR LIFE SUPPORT, AUTOMOTIVE SAFETY, SECURITY DEVICES, OR OTHER CRITICAL APPLICATIONS. PRODUCTS IN SUCH APPLICATIONS ARE UNDERSTOOD TO BE FULLY AT THE CUSTOMER OR THE CUSTOMER'S RISK. Apex Microtechnology, Apex and Apex Precision Power are trademarks of Apex Microtechnolgy, Inc. All other corporate names noted herein may be trademarks of their respective holders. www.apexanalog.com 4 Copyright (c) Apex Microtechnology, Inc. 2012 (All Rights Reserved) SEP 2012 VRE305DS VRE305DS REVH