Precision VOLTAGE REFERENCE

Transcription

1 Precision VOLTAGE REFERENCE FEATURES +.PUT HIGH ACCURACY: ±.V VERY LOW DRIFT: ppm/ C max EXCELLENT STABILITY: ppm/hrs LOW NOISE: µvp-p typ,.hz to Hz WIDE SUPPLY RANGE: Up to V LOW QUIESCENT CURRENT: ma max USEFUL MATCHED RESISTOR PAIR INCLUDED APPLICATIONS PRECISION CALIBRATED VOLTAGE STANDARD TRANSDUCER EXCITATION D/A AND A/D CONVERTER REFERENCE PRECISION CURRENT REFERENCE ACCURATE COMPARATOR THRESHOLD REFERENCE DIGITAL VOLTMETERS TEST EQUIPMENT DESCRIPTION The is a precision voltage reference which provides a +.V output. The drift is laser-trimmed to ppm/ C max (KM grade) over the full specification range. This is in contrast to some references which guarantee drift over a limited portion of their specification temperature range. The achieves its precision without a heater. This results in low quiescent current (.ma typ), fast warm-up (ms to.%), excellent stability (ppm/hrs typ), and low noise (µvp-p max,.hz to Hz). V TRIM R kω R kω R kω A The output can be adjusted with minimal effect on drift or stability. Additionally, the contains a matched pair of user-accessible precision resistors which are useful in a variety of applications. Single supply operation over.v to V supply range and excellent overall specifications make the an ideal choice for the most demanding applications such as precision system standards, D/A and A/D references, transducer excitation etc. V Z DZ Common R kω R B R A International Airport Industrial Park Mailing Address: PO Box Tucson, AZ Street Address: S. Tucson Blvd. Tucson, AZ Tel: () - Twx: 9-9- Cable: BBRCORP Telex: -9 FAX: () 9- Immediate Product Info: () - 9 Burr-Brown Corporation PDS-D Printed in U.S.A. October, 99

2 SPECIFICATIONS ELECTRICAL At T A = + C and +VDC power supply, unless otherwise noted. JM, KM, RM, SM PARAMETER CONDITIONS MIN TYP MAX UNITS OUTPUT VOLTAGE Initial T A = + C V Trim Range (). +. V vs Temperature () KM C to + C ppm/ C JM C to + C ppm/ C SM C to + C ppm/ C RM C to + C ppm/ C vs Supply (line regulation) V CC =. to V.. %/V vs Output Current (load regulation) I L = to ±ma.. %/ma vs Time T A = + C ppm/hrs NOISE.Hz to Hz µvp-p OUTPUT CURRENT Source or Sink ± ma INPUT VOLTAGE RANGE. V QUIESCENT CURRENT I OUT =. ma WARM-UP TIME To.% µs UNCOMMITTED RESISTORS Resistance kω Match ±. ±. % TCR ppm/ C TCR Tracking ppm/ C TEMPERATURE RANGE Specification JM, KM + C RM, SM + C Operating JM, KM + C RM, SM + C Storage + C NOTES : () Triming the offset voltage will affect the drift slightly. See Installation and Operating Instructions for details. () The box method is used to specify output voltage drift vs temperature. See the Discussion of Performance section. ORDERING INFORMATION TEMPERATURE MAX DRIFT MODEL PACKAGE RANGE (ppm/ C) JM Metal TO-99 C to + C KM Metal TO-99 C to + C RM Metal TO-99 C to + C SM Metal TO-99 C to + C PACKAGE INFORMATION PACKAGE DRAWING MODEL PACKAGE NUMBER () JM Metal TO-99 KM Metal TO-99 RM Metal TO-99 SM Metal TO-99 NOTE: () For detailed drawing and dimension table, please see end of data sheet, or Appendix D of Burr-Brown IC Data Book. ABSOLUTE MAXIMUM RATINGS Input Voltage... V Power Dissipation at + C... mw Operating Temperature Range JM, KM... C to + C RM, SM... C to + C Storage Temperature Range... C to + C Lead Temperature (soldering, s)... + C Short-Circuit Protection at + C To Common or +VDC... Continuous PIN CONFIGURATION Top View R B Tab V TRIM kω V Z kω kω.v Common R A Optional Voltage Trim TO-99 +V

3 NOISE TEST CIRCUIT OPTIONAL OUTPUT VOLTAGE FINE ADJUSTMENT CIRCUIT Ω kω The TCR of R S can effect drift if R S is made small. µf Tantalum µf OPA kω DUT µf.kω Gain = V/V f db =.Hz and Hz Oscilloscope () R S V TRIM Output Voltage +V NOTE: () See Output Voltage ment vs R S Curve. TYPICAL PERFORMANCE CURVES At T A = + C and +VDC power supply, unless otherwise noted. TYPICAL NOISE TYPICAL HEATED ZENER NOISE Noise Voltage (µv) Noise Voltage (µv) Low Frequency Noise (see Noise Test Ciruit) Low Frequency Noise (see Noise Test Ciruit) TYPICAL BANDGAP REFERENCE NOISE POWER TURN-ON RESPONSE Noise Voltage (µv) Error From Final Value (mv) Low Frequency Noise (see Noise Test Ciruit) Power Turn-On

4 TYPICAL PERFORMANCE CURVES (CONT) At T A = + C and +VDC power supply, unless otherwise noted. RESPONSE TO THERMAL SHOCK POWER SUPPLY REJECTION vs FREQUENCY Output Voltage Change (µv) T A = + C Device immersed in + C fluorinert bath. T A = + C Time (s) Power Supply Rejection (db) 9 k k k Frequency (Hz) LOAD REGULATION vs TEMPERATURE QUIESCENT CURRENT vs TEMPERATURE Load Regulation (ppm/ma) Negative Current (Sink) Positive Current (Sink) Quiescent Current (ma) Temperature ( C) Temperature ( C) Output Voltage ment (mv) k k OUTPUT VOLTAGE ADJUSTMENT vs R S See Optional Output Voltage Fine ment Circuit Voltage Increase Voltage Decrease Junction Temperature Rise Above Ambient ( C) JUNCTION TEMPERATURE RISE vs OUTPUT CURRENT Max. Temp. Rise for + C Ambient Max. Temp. Rise for + C Ambient V CC = V V CC = V V CC = V V CC = V V CC = V k k M R S (Ω) M M Output Current (ma)

5 THEORY OF OPERATION The following discussion refers to the diagram on the first page. In operation, approximately.v is applied to the noninverting input of op amp A by zener diode DZ. This voltage is amplified by A to produce the.v output. The gain is determined by R and R : G = (R + R )/R. R and R are actively laser-trimmed to produce an exact.v output. The zener operating current is derived from the regulated output voltage through R. This feedback arrangement provides closely regulated zener current. R is actively laser-trimmed to set the zener current to a level which results in low drift at the output of A. The adjustment of output voltage and zener current is interactive and several iterations may be used to achieve the desired results. R allows user-trimming of the output voltage by providing for a small external adjustment of amplifier gain. Since the TCR of R closely matches the TCR of the gain setting resistors, the voltage trim has minimal effect on the drift of the reference. DISCUSSION OF PERFORMANCE The is designed for applications requiring a precision voltage reference where both the initial value at room temperature and the drift over temperature are of importance to the user. Two basic methods of specifying voltage reference drift versus temperature are in common usage in the industry the butterfly method and the box method. Neither of these methods is entirely satisfactory in cases where the drift versus temperature is relatively nonlinear as is the case with most voltage references. The is specified with the more commonly used box method. The box is formed by the high and low specification temperatures and a diagonal, the slope of which is equal to the maximum specified drift. For the, each J and K unit is tested at temperatures of C, + C, + C, and + C, and each R and S unit is tested at C, C, C, + C, + C, + C, + C and + C. The minimum and maximum test voltages must meet this condition. ( MAX MIN )/V x drift specification T HIGH T LOW This assures the user that the variations of output voltage that occur as the temperature changes within the specification range T LOW to T HIGH will be contained within a box whose diagonal has a slope equal to the maximum specified drift. Since the shape of the actual drift curve is not known, the vertical position of the box is not exactly known either. It is, however, bounded by V UPPER BOUND and V LOWER BOUND (see Figure ). Figure uses the KM as an example. It has a drift specification of ppm/ C maximum and a specification temperature range of C to + C. The box height (V to V ) is µv and upper bound and lower bound voltages are a maximum of µv away from the voltage at + C. Output Voltage (V) +. V +. V Typical Drift Diagonal ppm/ C for KM V LOWER BOUND (T LOW ) (T HIGH ) Temperature ( C) FIGURE. KM Output Voltage Drift. INSTALLATION AND OPERATING INSTRUCTIONS BASIC CIRCUIT CONNECTION Figure shows the proper connection of the. To achieve the specified performance, pay careful attention to layout. A low resistance star configuration will reduce voltage errors, noise pickup, and noise coupled from the power supply. Commons should be connected as indicated being sure to minimize interconnection resistances. V CC + µf Tantalum V UPPER BOUND FIGURE. Basic Circuit Connection. () () µv Worst-case > for KM NOTES: () Lead resistance here of up to a few Ωs have negligible effect on performance. () A relatively constant current of approximately ma at ppm/ C flows in this lead. Ω in this lead would introduce about mv error (adjustable to zero) with about.ppm/ C drift at the output. () A resistance of.ω in series with these leads will cause a mv error when the load current is at its maximum of ma. This results in a.% error of V. () () () () R L R L R L

6 OPTIONAL OUTPUT VOLTAGE ADJUSTMENT Optional output voltage adjustment circuits are shown in Figures and. Trimming the output voltage will change the voltage drift by approximately. ppm/ C per mv of trimmed voltage. In the circuit in Figure, any mismatch in TCR between the two sections of the potentiometer will also affect drift, but the effect of the TCR is reduced by a factor of by the internal resistor divider. A high quality potentiometer, with good mechanical stability, such as a cermet, should be used. The circuit in Figure has a range of approximately +mv to mv. The circuit in Figure has less range but provides higher resolution. The mismatch in TCR between R S and the internal resistors can introduce some slight drift. This effect is minimized if R S is kept significantly larger than the kω internal resistor. A TCR of ppm/ C is normally sufficient. APPLICATION INFORMATION High accuracy, extremely-low drift, and small size make the ideal for demanding instrumentation and system voltage reference applications. Since no heater is required, low power supply current designs are readily achievable. Also the has lower output noise and much faster warm-up times (ms to.%) than heated references, permitting high precision without extra power from additional supplies. It should be considered that operating any integrated circuit at an elevated temperature will reduce its MTTF. A variety of application circuits are shown in Figures through 9. + µf Tantalum R kω C µf OPA = +V V TRIM Output Voltage +V f CO = =.Hz π RC FIGURE. Precision Reference with Filtering. Maximum range (+.%, %) and minimal degradation of drift. FIGURE. Optional Output Voltage ment. +V The TCR of R S can effect drift if R S is made small. OPA = V + µf Tantalum = V V () R S V TRIM Output Voltage +V = +V Higher resolution, reduced range. NOTE: () R S typically MΩ. See information in Typical Performance Curves. FIGURE. Optional Output Voltage Fine. FIGURE. ±V Reference. The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems.

7 +V OPA = +V DG OPA = +V or V = V = V CMOS Switch Logic Input = +V Logic +V V +V Auxiliary Output FIGURE. +V and +V Reference. FIGURE 9. Digitally-Controlled Bipolar Precision Reference. = V to V = V to V Ω N = +V N9.Ω = +V = +V Optional Trim I OUT = to +ma = +V FIGURE. +V Reference with Boosted Output Current to ma. = +V = +V N9 kω = V (Range of V to V).µF.V = +V FIGURE. Stacked References. FIGURE. +V Reference with Input Voltage Boost for V Operation.

8 = V +V R R Ladder resistor tolerances: All kω.% All Ω % MΩ kω V Ω +V OPA Ω kω kω V Ω I OUT = V/R where R = R R. I OUT may be raised up to ma by using external resistors. V I OUT Ω kω kω Ω V FIGURE. Positive Precision ma Current Source. Ω kω Ω V V IN to V R kω Zero OPA +V I OUT ma to ma Siliconex VN9AB Ω kω kω kω Ω kω.v.v OPA +V V = V V +V R.Ω Span Ω Ω Ω Ω kω kω Ω kω kω.v Ω kω kω.v V Ω kω.kω Ω NOTE: Tie all commons to one point. FIGURE. ma to ma Precision Current Transmitter. Ω kω kω.v FIGURE. Precision Voltage Calibrator.

9 = V +V Ω OPA +V +V Out Ω V Ω V Out Ω Ω FIGURE. ±V Reference. +V At.V, the Ω bridge requires.ma. An Ω resistor connected directly from the bridge to the positive supply provides the bulk of the bridge current. The need only supply an error current to keep the bridge at.v. Since the can sink or source up to ma, the circuit shown can tolerate supply variations of up to V, ±V, or bridge resistance drift from Ω to Ω. +V FIGURE. +V Reference with Output Current Boost Using a Resistor to Drive a Ω Bridge. R + R R OPA + FIGURE. +V and +V Reference. R G.µF +V kω = R X R G R kω Gain +V VFC V + to khz Output pf NOTE: Tame Transducer Bridge Errors with Op Amp Control, EDN, May, 9, Jerald Graeme. ±V Input FIGURE. Linear Bridge Circuit Using Internal Precision Resistors of the as the Bridge Completion Network. FIGURE 9. Bipolar Input Voltage-to-Frequency Converter. 9

10 PACKAGE DRAWING