VRE204 VRE204 P r o d u c t IInnnnoovvaa t i o n FFr roomm Precision Voltage Reference Features ♦ Very High Accuracy: +4.5 V Output, ±0.4 mV ♦ Extremely Low Drift: 0.6 ppm/°C (-55°C to +125°C) ♦ Excellent Stability: 6 ppm/1000 Hrs. Typical ♦ Excellent Line Regulation: 6 ppm/V Typical ♦ Wide Supply Range: ±13.5 V to ±22.0 V ♦ Hermetic 20-terminal Ceramic LCC ♦ Military Processing Available 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 DESCRIPTION VRE204 Series Precision Voltage References provide ultrastable +4.5 V outputs with up to ±0.4 mV initial accuracy and temperature coefficient as low as 0.6 ppm/°C over the full military temperature range. These references are specifically designed to be used with successive-approximation type Analog-to-Digital Converters (ADCs). Specify an ADC with exceptional temperature drift, which can only be as good as the external reference used. The VRE204 combined with the right ADC will provide the lowest drift data conversion obtainable. The VRE204 series is available in the military operating temperature range -55°C to +125°C, and two performance grades. All devices are packaged in 20-terminal LCC ceramic packages for maximum long-term stability. These “M” versions are screened for high reliability and quality. Superior stability, accuracy, and quality make the VRE204 ideal for all precision applications which may require a 4.5 V reference. High-accuracy test and measurement instrumentation, and transducer excitation are some other applications which can benefit from the high accuracy of the VRE204. Figure 1. BLOCK DIAGRAM 11 Selection Guide Model VRE204M VRE204MA VRE204DS Output (V) Temperature Operating Range Volt Deviation (MAX) +4.5V +4.5V -55°C to +125°C -55°C to +125°C ±0.6mV ±0.3mV http://www.cirrus.com Copyright © Cirrus Logic, Inc. 2009 (All Rights Reserved) 20-terminal Ceramic LCC Package Style HD JUL 20091 APEX − VRE204DSREVG VRE204 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 = +25°C, RL = 10K Ω Unless Otherwise Noted. Model M Parameter Min Typ MA Max Min +13.5 +22 Operating Temperature -55 Storage Temperature -65 Typ Max Units * * V +125 * * ºC +150 * * ºC ABSOLUTE MAXIMUM RATINGS Power Supply Short Circuit Protection Continuous * +4.5 * OUTPUT VOLTAGE VRE204 V OUTPUT VOLTAGE ERRORS Initial Error ±800 Warmup Drift TMIN - TMAX ±400 2 (Note1) 1 600 µV ppm 300 µV Long-Term Stability 6 * ppm/1000hrs. Noise (0.1 - 10Hz) 3 * µVpp OUTPUT CURRENT Range ±10 * mA REGULATION Line 6 Load 3 10 * * * ppm/V Range 10 * mV Temperature Coefficient 4 * µV/ºC/mV ppm/mA OUTPUT ADJUSTMENT POWER SUPPLY CURRENT (Note 2) VRE204 +PS 5 7 * * mA NOTES: * Same as M Models. 1. Using the box method, the specified value is the maximum deviation from the output voltage at 25°C over the specified operating temperature range. 2. The specified values are unloaded. 2 VRE204DS VRE204 P r o d u c t I n n o v a t i o nF r o m 2. TYPICAL PERFORMANCE GRAPHS VOUT vs. TEMPERATURE VOUT vs. TEMPERATURE Temperature oC VRE204M Temperature oC VRE204MA QUIESCENT CURRENT VS. TEMP Temperature oC JUNCTION TEMP. RISE VS. OUTPUT CURRENT 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 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 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 then adjusting the slope, the VRE204 series 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. By using highly stable resistors in our network, we produce a voltage reference that also has very good long term stability. VRE204DS 3 VRE204 P r o d u c t I n n o v a t i o nF r o m 4. APPLICATION INFORMATION The proper connection of the VRE204 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 VRE204 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 3 2 1 20 4 +15V Ref. Gnd. PIN CONFIGURATION NC NC NC VOUT NC 19 18 18 17 16 15 14 5 17 NC 19 13 NC 6 16 NC 20 12 NC 7 15 8 14 9 10 11 12 13 VOUT = +4.5V 10KΩ NC 1 NC 2 NC 3 VRE204 11 TRIM TOP VIEW 10 GND Δ 4 9 5 NC VIN 6 7 REF GND 8 NC NC NC 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. 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