a Low Noise Micropower Precision Voltage Reference ADR293 PIN CONFIGURATIONS FEATURES Voltage Output 5.0 V 6.0 V to 15 V Supply Range Supply Current 15 mA Max Initial Accuracy 63 mV Max Temperature Coefficient 8 ppm/8C Max Low Noise 15 mV p–p Typ (0.1 Hz to 10 Hz) High Output Current 5 mA Min Temperature Range 2408C to 11258C REF02/REF19x Pinout 8-Lead Narrow Body SO (R Suffix) 8 NC NC 1 ADR293 VIN 2 7 NC TOP VIEW NC 3 (Not to Scale) 6 VOUT GND 4 5 NC NC = NO CONNECT APPLICATIONS Portable Instrumentation Precision Reference for 5 V Systems A/D and D/A Converter Reference Solar Powered Applications Loop-Current Powered Instruments 8-Lead TSSOP (RU Suffix) 8 NC NC 1 ADR293 VIN 2 7 NC TOP VIEW (Not to Scale) 6 VOUT 3 NC GENERAL DESCRIPTION The ADR293 is a low noise, micropower precision voltage reference that utilizes an XFET™ (eXtra implanted junction FET) reference circuit. The new XFET architecture offers significant performance improvements over traditional bandgap and Zener-based references. Improvements include: one quarter the voltage noise output of bandgap references operating at the same current, very low and ultralinear temperature drift, low thermal hysteresis and excellent long-term stability. The ADR293 is a series voltage reference providing stable and accurate output voltage from a 6.0 V supply. Quiescent current is only 15 µA max, making this device ideal for battery powered instrumentation. Three electrical grades are available offering initial output accuracy of ± 3 mV, ± 6 mV, and ± 10 mV. Temperature coefficients for the three grades are 8 ppm/°C, 15 ppm/°C and 25 ppm/°C max. Line regulation and load regulation are typically 30 ppm/V and 30 ppm/mA, maintaining the reference’s overall high performance. The ADR293 is specified over the extended industrial temperature range of –40°C to +125°C. This device is available in the 8-lead SOIC, 8-lead TSSOP and the TO-92 package. GND 4 5 NC NC = NO CONNECT 3-Lead TO-92 (T9 Suffix) PIN 1 PIN 2 VIN GND PIN 3 VOUT BOTTOM VIEW Part Number Nominal Output Voltage (V) ADR290 ADR291 ADR292 ADR293 2.048 2.500 4.096 5.000 XFET is a trademark of Analog Devices, Inc. REV. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 1998 ADR293–SPECIFICATIONS ELECTRICAL SPECIFICATIONS (V = 16.0 V, T = 1258C unless otherwise noted) S A Parameter Symbol Conditions Min Typ Max Units INITIAL ACCURACY “E” Grade “F” Grade “G” Grade VO IOUT = 0 mA 4.997 4.994 4.990 5.000 5.003 5.006 5.010 V V V LINE REGULATION “E/F” Grades “G” Grade ∆VO/∆VIN 6.0 V to 15 V, IOUT = 0 mA 30 40 100 150 ppm/V ppm/V LOAD REGULATION “E/F” Grades “G” Grade ∆VO/∆ILOAD VS = 6.0 V, 0 mA to 5 mA 30 40 100 150 ppm/mA ppm/mA LONG TERM STABILITY ∆VO 1000 hrs @ +25°C, VS = +15 V 0.2 ppm NOISE VOLTAGE eN 0.1 Hz to 10 Hz 15 µV p-p WIDEBAND NOISE DENSITY eN at 1 kHz 640 nV/√Hz ELECTRICAL SPECIFICATIONS (V = 16.0 V, T = 2258C ≤ T ≤ 1858C unless otherwise noted) S A A Parameter Symbol Conditions TEMPERATURE COEFFICIENT “E” Grade “F” Grade “G” Grade TCVO/°C LINE REGULATION “E/F” Grades “G” Grade LOAD REGULATION “E/F” Grades “G” Grade Min Typ Max Units IOUT = 0 mA 3 5 10 8 15 25 ppm/°C ppm/°C ppm/°C ∆VO/∆VIN 6.0 V to 15 V, IOUT = 0 mA 35 50 150 200 ppm/V ppm/V ∆VO/∆ILOAD VS = 6.0 V, 0 mA to 5 mA 20 30 150 200 ppm/mA ppm/mA Typ Max Units ELECTRICAL SPECIFICATIONS (V = 16.0 V, T = 2408C ≤ T ≤ 11258C unless otherwise noted) S A A Parameter Symbol Conditions Min TEMPERATURE COEFFICIENT “E” Grade “F” Grade “G” Grade TCVO/°C IOUT = 0 mA 3 5 10 10 20 30 ppm/°C ppm/°C ppm/°C LINE REGULATION “E/F” Grades “G” Grade ∆VO/∆VIN 6.0 V to 15 V, IOUT = 0 mA 40 70 200 250 ppm/V ppm/V LOAD REGULATION “E/F” Grades “G” Grade ∆VO/∆ILOAD VS = 6.0 V, 0 mA to 5 mA 20 30 200 300 ppm/mA ppm/mA SUPPLY CURRENT @ +25°C 11 15 15 20 µA µA THERMAL HYSTERESIS TO-92 SO-8 TSSOP-8 160 72 157 ppm ppm ppm Specifications subject to change without notice. –2– REV. 0 ADR293 WAFER TEST LIMITS (V = 16.0 V, T = 1258C unless otherwise noted) S A Parameter Symbol Conditions Limits Units INITIAL ACCURACY VO IOUT = 0 mA 4.990/5.010 V LINE REGULATION ∆VO/∆VIN 6.0 V < VIN < 15 V, IOUT = 0 mA 150 ppm/V LOAD REGULATION ∆VO/∆ILOAD 0 mA to 5 mA 150 ppm/mA No load 15 µA SUPPLY CURRENT NOTES Electrical tests are performed as wafer probe to the limits shown. Due to variations in assembly methods and normal yield loss, yield after packaging is not guaranteed for standard product dice. Consult factory to negotiate specifications based on dice lot qualification through sample lot assembly and testing. Specifications subject to change without notice. DICE CHARACTERISTICS Die Size 0.074 3 0.052 inch, 3848 sq. mils (1.88 3 1.32 mm, 2.48 sq. mm) Transistor Count: 52 VIN 1 4 3 GND REV. 0 2 –3– VOUT(SENSE) VOUT(FORCE) ADR293 ABSOLUTE MAXIMUM RATINGS 1 Supply Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 V Output Short-Circuit Duration . . . . . . . . . . . . . . . . . Indefinite Storage Temperature Range T9, R, RU Package . . . . . . . . . . . . . . . . . 265°C to 1150°C Operating Temperature Range . . . . . . . . . . 240°C to 1125°C Junction Temperature Range T9, R, RU Package . . . . . . . . . . . . . . . . . 265°C to 1125°C Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . 1300°C Package Type uJA1 uJC Units 8-Lead SOIC (R) 3-Lead TO-92 (T9) 8-Lead TSSOP (RU) 158 162 240 43 120 43 °C/W °C/W °C/W NOTE 1 θJA is specified for worst case conditions, i.e., θJA is specified for device in socket for PDIP, and θJA is specified for a device soldered in circuit board for SOIC packages. NOTE 1 Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ORDERING GUIDE Model Temperature Range Package Type Package Options ADR293ER, ADR293FR, ADR293GR ADR293ER-REEL, ADR293FR-REEL, ADR293GR-REEL ADR293ER-REEL7, ADR293FR-REEL7, ADR293GR-REEL7 ADR293GT9 ADR293GT9-REEL ADR293GRU-REEL ADR293GRU-REEL7 ADR293GBC 240°C to 1125°C 240°C to 1125°C 240°C to 1125°C 240°C to 1125°C 240°C to 1125°C 240°C to 1125°C 240°C to 1125°C 125°C 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 3-Lead TO-92 3-Lead TO-92 8-Lead TSSOP 8-Lead TSSOP DICE R-8 R-8 R-8 T9 T9 RU-8 RU-8 CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the ADR293 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. –4– WARNING! ESD SENSITIVE DEVICE REV. 0 Typical Performance Characteristics– ADR293 5.006 100 VS = 6.0V 3 TYPICAL PARTS VS = 6.0V TO 15V LINE REGULATION – ppm/V OUTPUT VOLTAGE – V 5.004 5.002 5.000 4.998 80 60 40 20 4.996 4.994 250 225 0 25 50 75 100 0 250 125 225 0 TEMPERATURE – 8C 25 50 75 100 125 TEMPERATURE – 8C Figure 1. VOUT vs. Temperature Figure 4. Line Regulation vs. Temperature 16 100 VS = 6.0V TO 9.0V 14 LINE REGULATION – ppm/V TA = +1258C 12 SUPPLY CURRENT – mA IOUT = 0mA TA = +258C 10 TA = 2408C 8 6 4 IOUT = 0mA 80 60 40 20 2 0 0 2 4 6 8 10 INPUT VOLTAGE – V 12 14 0 250 16 225 0 25 50 75 100 125 TEMPERATURE – 8C Figure 2. Supply Current vs. Input Voltage Figure 5. Line Regulation vs. Temperature 16 0.7 VS = 6.0V 0.6 DIFFERENTIAL VOLTAGE – V SUPPLY CURRENT – mA 14 12 10 8 TA = +1258C 0.5 0.4 TA = +258C 0.3 0.2 TA = 2408C 0.1 6 250 225 0 25 50 75 100 0 125 0 TEMPERATURE – 8C Figure 3. Supply Current vs. Temperature REV. 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 LOAD CURRENT – mA 4.0 4.5 5.0 Figure 6. Minimum Input-Output Voltage Differential vs. Load Current –5– ADR293 120 200 VS = 6.0V VS = 6.0V 160 RIPPLE REJECTION – dB LOAD REGULATION – ppm/mA 100 120 IOUT = 5mA 80 IOUT = 1mA 80 60 40 40 20 0 250 225 0 25 50 75 100 0 10 125 100 FREQUENCY – Hz TEMPERATURE – 8C Figure 10. Ripple Rejection vs. Frequency Figure 7. Load Regulation vs. Temperature 2 50 VS = 6.0V IL = 0mA 1 40 OUTPUT IMPEDANCE – V DVOUT FROM NOMINAL – mV 1000 0 TA = +258C 21 TA = 2408C TA = +1258C 22 20 10 23 24 30 0 1 SOURCING LOAD CURRENT – mA 0 10 10 Figure 8. ∆VOUT from Nominal vs. Load Current 100 1k FREQUENCY – Hz 10k Figure 11. Output Impedance vs. Frequency VOLTAGE NOISE DENSITY – nV/ Hz 1200 VIN = 15V TA = 1258C 1000 800 10mV p-p 600 400 200 0 10 1s 100 FREQUENCY – Hz 1000 Figure 9. Voltage Noise Density Figure 12. 0.1 Hz to 10 Hz Noise –6– REV. 0 ADR293 IL = 5mA IL = 5mA CL = 1nF 5V/DIV 2V/DIV 50ms 1ms Figure 13. Turn-On Time Figure 16. Load Transient IL = 5mA IL = 5mA CL = 100nF 5V/DIV 2V/DIV 50ms 1ms Figure 17. Load Transient Figure 14. Turn-Off Time IL = 5mA 1ms Figure 15. Load Transient REV. 0 –7– ADR293 THEORY OF OPERATION Device Power Dissipation Considerations The ADR293 uses a new reference generation technique known as XFET, which yields a reference with low noise, low supply current and very low thermal hysteresis. The ADR293 is guaranteed to deliver load currents to 5 mA with an input voltage that ranges from 5.5 V to 15 V. When this device is used in applications with large input voltages, care should be exercised to avoid exceeding the published specifications for maximum power dissipation or junction temperature that could result in premature device failure. The following formula should be used to calculate a device’s maximum junction temperature or dissipation: The core of the XFET reference consists of two junction fieldeffect transistors one of which has an extra channel implant to raise its pinch-off voltage. By running the two JFETS at the same drain current, the difference in pinch-off voltage can be amplified and used to form a highly stable voltage reference. The intrinsic reference voltage is around 0.5 V with a negative temperature coefficient of about –120 ppm/K. This slope is essentially locked to the dielectric constant of silicon and can be closely compensated by adding a correction term generated in the same fashion as the proportional-to-temperature (PTAT) term used to compensate bandgap references. The big advantage over a bandgap reference is that the intrinsic temperature coefficient is some thirty times lower (therefore less correction is needed) and this results in much lower noise since most of the noise of a bandgap reference comes from the temperature compensation circuitry. The simplified schematic below shows the basic topology of the ADR293. The temperature correction term is provided by a current source with value designed to be proportional to absolute temperature. The general equation is: PD = T J −TA θJA In this equation, TJ and TA are the junction and ambient temperatures, respectively, PD is the device power dissipation, and θJA is the device package thermal resistance. Basic Voltage Reference Connections References, in general, require a bypass capacitor connected from the VOUT pin to the GND pin. The circuit in Figure 19 illustrates the basic configuration for the ADR293. Note that the decoupling capacitors are not required for circuit stability. NC 1 R1 + R2 + R3 = ∆VP + I PTAT R3 R1 ( I1 I1 NC OUTPUT NC + 10mF 3 6 4 5 0.1mF where ∆VP is the difference in pinch-off voltage between the two FETs and IPTAT is the positive temperature coefficient correction current. VIN 7 ADR293 )( ) The process used for the XFET reference also features vertical NPN and PNP transistors, the latter of which are used as output devices to provide a very low drop-out voltage. NC INPUT 2 VOUT 8 NC 0.1mF NC = NO CONNECT Figure 19. Basic Voltage Reference Configuration Noise Performance The noise generated by the ADR293 is typically less than 15 µVp-p over the 0.1 Hz to 10 Hz band. The noise measurement is made with a bandpass filter made of a 2-pole high-pass filter with a corner frequency at 0.1 Hz and a 2-pole low-pass filter with a corner frequency at 10 Hz. Turn-On Time * VOUT DVP R1 IPTAT R2 Upon application of power (cold start), the time required for the output voltage to reach its final value within a specified error band is defined as the turn-on settling time. Two components normally associated with this are; the time for the active circuits to settle, and the time for the thermal gradients on the chip to stabilize. Figure 13 shows the typical turn-on time for the ADR293. R3 *EXTRA CHANNEL IMPLANT VOUT 5 R11 R21R3 R1 GND 3 DVP1 I PTAT 3 R3 Figure 18. Simplified Schematic –8– REV. 0 ADR293 APPLICATIONS A Negative Precision Reference without Precision Resistors A Precision Current Source Many times in low power applications, the need arises for a precision current source that can operate on low supply voltages. As shown in Figure 21, the ADR293 is configured as a precision current source. The circuit configuration illustrated is a floating current source with a grounded load. The reference’s output voltage is bootstrapped across RSET, which sets the output current into the load. With this configuration, circuit precision is maintained for load currents in the range from the reference’s supply current, typically 15 µA to approximately 5 mA. In many current-output CMOS DAC applications where the output signal voltage must be of the same polarity as the reference voltage, it is often required to reconfigure a currentswitching DAC into a voltage-switching DAC through the use of a 1.25 V reference, an op amp and a pair of resistors. Using a current-switching DAC directly requires the need for an additional operational amplifier at the output to reinvert the signal. A negative voltage reference is then desirable from the point that an additional operational amplifier is not required for either reinversion (current-switching mode) or amplification (voltage-switching mode) of the DAC output voltage. In general, any positive voltage reference can be converted into a negative voltage reference through the use of an operational amplifier and a pair of matched resistors in an inverting configuration. The disadvantage to that approach is that the largest single source of error in the circuit is the relative matching of the resistors used. VIN 2 ADR293 6 VOUT The circuit illustrated in Figure 20 avoids the need for tightly matched resistors with the use of an active integrator circuit. In this circuit, the output of the voltage reference provides the input drive for the integrator. The integrator, to maintain circuit equilibrium, adjusts its output to establish the proper relationship between the reference’s VOUT and GND. One caveat with this approach should be mentioned: although rail-to-rail output amplifiers work best in the application, these operational amplifiers require a finite amount (mV) of headroom when required to provide any load current. The choice for the circuit’s negative supply should take this issue into account. 4 ISY P1 IOUT VOUT 4 1mF +5V 100V 100kV 1mF A1 –VREF –5V A1 = 1/2 OP291, 1/2 OP295 Figure 20. A Negative Precision Voltage Reference Uses No Precision Resistors REV. 0 RSET Figure 21. A Precision Current Source 6 GND 6 RL 2 1kV 1mF ADJUST VIN ADR293 R1 GND –9– ADR293 Kelvin Connections Voltage Regulator For Portable Equipment In many portable instrumentation applications where PC board cost and area go hand-in-hand, circuit interconnects are very often of dimensionally minimum width. These narrow lines can cause large voltage drops if the voltage reference is required to provide load currents to various functions. In fact, a circuit’s interconnects can exhibit a typical line resistance of 0.45 mW/square (1 oz. Cu, for example). Force and sense connections also referred to as Kelvin connections, offer a convenient method of eliminating the effects of voltage drops in circuit wires. Load currents flowing through wiring resistance produce an error (VERROR = R 3 IL ) at the load. However, the Kelvin connection of Figure 22 overcomes the problem by including the wiring resistance within the forcing loop of the op amp. Since the op amp senses the load voltage, op amp loop control forces the output to compensate for the wiring error and to produce the correct voltage at the load. The ADR293 is ideal for providing a stable, low cost and low power reference voltage in portable equipment power supplies. Figure 23 shows how the ADR293 can be used in a voltage regulator that not only has low output noise (as compared to switch mode design) and low power, but also a very fast recovery after current surges. Some precautions should be taken in the selection of the output capacitors. Too high an ESR (effective series resistance) could endanger the stability of the circuit. A solid tantalum capacitor, 16 V or higher, and an aluminum electrolytic capacitor, 10 V or higher, are recommended for C1 and C2, respectively. Also, the path from the ground side of C1 and C2 to the ground side of R1 should be kept as short as possible. CHARGER INPUT 0.1mF VIN RLW 2 LEAD-ACID BATTERY VIN ADR293 A1 6 VOUT + 2 7 3 4 ADR293 IRF9530 6 OP-20 GND +VOUT FORCE +5V, 100mA 4 R2 R1 402kV 402kV 1% 1% RL 1mF V OUT 6 6V +VOUT SENSE RLW GND R3 510kV 2 VIN C1 68mF TANT + + C2 1000mF ELECT 100kV 4 Figure 23. Voltage Regulator for Portable Equipment A1 = 1/2 OP295 Figure 22. Advantage of Kelvin Connection –10– REV. 0 ADR293 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 8-Lead TSSOP (RU-8) 0.122 (3.10) 0.114 (2.90) 5 1 4 PIN 1 8 0.1574 (4.00) 0.1497 (3.80) 0.177 (4.50) 0.169 (4.30) 8 0.102 (2.59) 0.094 (2.39) 0.0098 (0.25) 0.0040 (0.10) 0.0500 0.0192 (0.49) SEATING (1.27) 0.0138 (0.35) 0.0098 (0.25) PLANE BSC 0.0075 (0.19) 0.0196 (0.50) x 45° 0.0099 (0.25) 1 5 0.256 (6.50) 0.246 (6.25) 0.1968 (5.00) 0.1890 (4.80) 0.2440 (6.20) 0.2284 (5.80) C3347–8–6/98 8-Lead Narrow Body SO (R-8) 4 PIN 1 8° 0° 0.006 (0.15) 0.002 (0.05) 0.0500 (1.27) 0.0160 (0.41) SEATING PLANE 0.0256 (0.65) BSC 0.0433 (1.10) MAX 0.0118 (0.30) 0.0075 (0.19) 0.0079 (0.20) 0.0035 (0.090) 88 08 0.028 (0.70) 0.020 (0.50) 3-Lead TO-92 (T9 Suffix) 0.205 (5.20) 0.175 (4.96) 0.135 (3.43) MIN 0.210 (5.33) 0.170 (4.38) 0.050 (1.27) MAX SEATING PLANE 0.019 (0.482) 0.016 (0.407) SQUARE 0.500 (12.70) MIN 0.055 (1.39) 0.045 (1.15) 0.105 (2.66) 0.095 (2.42) 0.105 (2.66) 0.080 (2.42) 1 2 3 BOTTOM VIEW REV. 0 –11– 0.165 (4.19) 0.125 (3.94) PRINTED IN U.S.A. 0.105 (2.66) 0.080 (2.42)