VRE304 VRE304 P r o d u c t IInnnnoovvaa t i o n FFr roomm Precision Voltage Reference Features ♦ +4.5 V Output, ± 0.450 mV (.01%) ♦ Temperature Drift: 0.6 ppm/ºC ♦ Low Noise: 3μVp-p (0.1-10Hz) ♦ Industry Standard Pinout: 8-Pin Surface Mount Package ♦ Excellent Line Regulation: 6 ppm/V Typical ♦ Output Trim Capability Applications The VRE304 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 VRE304 offers superior performance over monolithic references. DESCRIPTION The VRE304 is a low cost, high precision +4.5 V reference. Available in an industry standard 8-pin surface mount package, the device is ideal for upgrading systems that use lower performance references. The device provides ultrastable +4.5 V output with ±0.45 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. For enhanced performance, the VRE304 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 Initial Error (mV) Temp. Coeff. (ppm/ºC) Temp. Range (ºC) ±0.45 ±0.90 0.6 2.0 0ºC to +70ºC 0ºC to +70ºC VRE304A VRE304C VRE304DS http://www.cirrus.com Copyright © Cirrus Logic, Inc. 2009 (All Rights Reserved) 8-pin Surface Mount Package Style GD MAR 2009 APEX − VRE304DSREVE VRE304 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 = +25ºC, RL = 10KΩ Unless Otherwise Noted. Model A Parameter C Min Typ Max Min Typ Max Units ±13.5 ±15 ±22 * * * V +70 * * ºC +150 * * ºC ABSOLUTE MAXIMUM RATINGS Power Supply Operating Temperature 0 Storage Temperature -65 Short Circuit Protection Continuous * +4.5 * V 630 * mV OUTPUT VOLTAGE VRE304 (Note 1) Temp. Sensor Voltage OUTPUT VOLTAGE ERRORS Initial Error (Note 2) ±0.45 Warmup Drift ±0.90 1 TMIN - TMAX 3 (Note3) Noise (0.1 - 10Hz) ppm 0.6 Long-Term Stability (Note 4) mV 2.0 ppm/ºC 6 * ppm/1000hrs. 3 * µVpp 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) VRE304 +PS 5 7 * * mA NOTES: * Same as A Model. 1. The temp. reference TC is 2.1 mV/ ºC 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. VRE304DS VRE304 P r o d u c t I n n o v a t i o nF r o m 2. TYPICAL PERFORMANCE CURVES VOUT vs. TEMPERATURE VOUT vs. TEMPERATURE Temperature oC VRE304A Temperature oC VRE304C JUNCTION TEMP. RISE VS. OUTPUT CURRENT QUIESCENT CURRENT VS. TEMP Temperature oC Output Current (mA) 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 4.5 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. VRE304DS VRE304 P r o d u c t I n n o v a t i o nF r o m The proper connection of the VRE304 series voltage references with the optional trim resistor for initial error and the optional capacitor for noise reduction is shown below. The VRE304 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 20ppm. 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 V TEMP OUT 2 OPTIONAL NOISE REDUCTION CAPACITOR CΝ 1µF PIN CONFIGURATION 3 8 + VOUT 6 VRE304 10kΩ 5 1 +VIN 2 TEMP 3 GND 4 VRE304 TOP VIEW 8 NOISE REDUCTION 7 REF. GND 6 VOUT 5 TRIM OPTIONAL FINE TRIM ADJUSTMENT 4 7 N/C REF. GND 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 [email protected]. 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. 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