VRE104 Precision Reference Supplies THALER CORPORATION • 2015 N. FORBES BOULEVARD • TUCSON, AZ. 85745 • (520) 882-4000 FEATURES APPLICATIONS • VERY HIGH ACCURACY: 4.5000 V OUTPUT ±0.4 mV • PRECISION A/D and D/A CONVERTERS • EXTREMELY LOW DRIFT: 0.6 ppm/°C -55°C to +125°C • TRANSDUCER EXCITATION • EXCELLENT STABILITY: 6 ppm/1000 Hrs. Typ. • ACCURATE COMPARATOR THRESHOLD REFERENCE • EXCELLENT LINE REGULATION: 6 ppm/V Typ. • WIDE SUPPLY RANGE: +13.5 to +22.0 V • HERMETIC 14-PIN CERAMIC DIP • MILITARY PROCESSING OPTIONS • HIGH RESOLUTION SERVO SYSTEMS • DIGITAL VOLTMETERS • HIGH PRECISION TEST and MEASUREMENT INSTRUMENTS DESCRIPTION VRE104 Series Precision Voltage References provide ultrastable +4.500 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 the Crystal Semiconductor line of successive-approximation type Analog to Digital Converters (ADCs). This line of ADCs sets new standards for temperature drift, which can only be as good as the external reference used. The Thaler VRE104 combined with a Crystal ADC will provide the lowest drift data conversion obtainable. SELECTION GUIDE Type Output Temperature Max. Volt Operating Range Deviation VRE104C VRE104CA +4.5V +4.5V -25°C to +85°C -25°C to +85°C 0.4mV 0.2mV VRE104M VRE104MA +4.5V +4.5V -55°C to +125°C -55°C to +125°C 0.6mV 0.3mV VRE104 series devices are available in two operating temperature ranges, -25°C to +85°C and -55°C to +125°C, and two performance grades. All devices are packaged in 14-pin hermetic ceramic packages for maximum long-term stability. "M" versions are screened for high reliability and quality. Superior stability, accuracy, and quality make the VRE104 ideal for all precision applications which may require a 4.5V reference. High-accuracy test and measurement instrumentation, and transducer excitation are some other applications which can benefit from the high accuracy of the VRE104. VRE104DS REV. C SEPT 1994 ELECTRICAL SPECIFICATIONS VRE104 Vps =+15V, T = 25°C, RL = 10KΩ unless otherwise noted. MODEL C PARAMETERS MIN CA TYP MAX M MIN TYP MAX MIN * * * * * * MA TYP MAX MIN TYP MAX UNITS ABSOLUTE MAXIMUM RATINGS Power Supply +13.5 +22 Operating Temperature -25 85 Storage Temperature -65 150 Short Circuit Protection Continuous * -55 * * 125 * * -55 * * 125 * * * * * * * V °C °C OUTPUT VOLTAGE VRE104 +4.5 V OUTPUT VOLTAGE ERRORS Initial Error Warmup Drift Tmin - Tmax (1) Long-Term Stability Noise (.1-10Hz) 800 400 2 800 1 400 200 6 3 400 2 1 600 * * 300 * * * * µV ppm µV ppm/1000hrs µVpp OUTPUT CURRENT Range ±10 * * * mA REGULATION Line Load 6 3 10 * * * * * * * * * ppm/V ppm/mA OUTPUT ADJUSTMENT Range Temperature Coeff. POWER SUPPLY CURRENTS 10 4 * * * * mV µV/°C/mV (2) VRE104 +PS NOTES: * * 5 7 * * * * * * mA *Same as C 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. VRE104DS REV. C SEPT 1994 TYPICAL PERFORMANCE CURVES VOUT vs. TEMPERATURE VOUT vs. TEMPERATURE VOUT vs. TEMPERATURE VOUT vs. TEMPERATURE Temperature oC VRE104C Temperature oC VRE104CA Temperature oC VRE104M Temperature oC VRE104MA QUIESCENT CURRENT VS. TEMP Temperature oC JUNCTION TEMP. RISE VS. OUTPUT CURRENT Output Current (mA) PSRR VS. FREQUENCY Frequency (Hz) VRE104 Used With Crystal Semiconductor ADC Suggested Reading: Crystal Semiconductor Application Note: “Voltage References for the CS501X/CS25IIX Series of A/D Converters VRE104DS REV. C SEPT 1994 DISCUSSION OF PERFORMANCE THEORY OF OPERATION APPLICATION INFORMATION The following discussion refers to the schematic below. 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 4.5000V 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. Figure 2 shows the proper connection of the VRE104 series voltage references with the optional trim resistors. Pay careful attention to the circuit layout to avoid noise pickup and voltage drops in the lines. 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 method leaves a residual error over wide temperature ranges. To remove this residual error, Thaler has developed a nonlinear compensation network of thermistors and resistors that is used in the VRE104 series references. This proprietary network eliminates most of the nonlinearity in the voltage vs. temperature function. By then adjusting the slope, Thaler Corporation 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. The VRE104 series voltage references have the ground terminal brought out on two pins (pin 6 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 7 to the power supply ground and pin 6 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. VRE104 FIGURE 1 VRE104DS REV. C SEPT 1994 EXTERNAL CONNECTIONS FIGURE 2 1. Optional Fine Adjust for approximately ±10mV. PIN CONFIGURATION TOP VIEW NC FINE ADJ. NC +4.5V FINE ADJ. NC NC VRE104 +PS NC NC REF. GND NC GND NC MECHANICAL 14-PIN HYBRID PACKAGE INCHES MILLIMETER INCHES MILLIMETER DIM MIN MAX MIN MAX DIM MIN MAX MIN MAX E .480 .500 12.1 12.7 A .120 .155 3.0 4.0 L .195 .215 4.9 5.4 Q .015 .035 0.4 0.9 D .775 .805 19.7 20.4 Q1 N/A .030 N/A 0.7 B .016 .020 0.4 0.5 C .009 .012 0.2 0.3 B1 .038 .042 0.9 1.0 G1 .290 .310 7.3 7.8 B2 .095 .105 2.4 2.6 S .085 .105 2.1 2.6 P .004 .006 0.10 0.15 VRE104DS REV. C SEPT 1994