Ultraprecision, Low Noise, 2.048 V/2.500 V/ 3.00 V/5.00 V XFET(R) Voltage References ADR420/ADR421/ADR423/ADR425 FEATURES PIN CONFIGURATION Low noise (0.1 Hz to 10 Hz) ADR420: 1.75 V p-p ADR421: 1.75 V p-p ADR423: 2.0 V p-p ADR425: 3.4 V p-p Low temperature coefficient: 3 ppm/C Long-term stability: 50 ppm/1,000 hours Load regulation: 70 ppm/mA Line regulation: 35 ppm/V Low hysteresis: 40 ppm typical Wide operating range ADR420: 4 V to 18 V ADR421: 4.5 V to 18 V ADR423: 5 V to 18 V ADR425: 7 V to 18 V Quiescent current: 0.5 mA maximum High output current: 10 mA Wide temperature range: -40C to +125C TP 1 VIN 2 ADR420/ ADR421/ ADR423/ ADR425 8 TP 7 NIC VOUT TOP VIEW GND 4 (Not to Scale) 5 TRIM NIC = NO INTERNAL CONNECTION TP = TEST PIN (DO NOT CONNECT) 02432-001 NIC 3 6 Figure 1. 8-Lead SOIC, 8-Lead MSOP GENERAL DESCRIPTION The ADR42x are a series of ultraprecision, second-generation eXtra implanted junction FET (XFET) voltage references featuring low noise, high accuracy, and excellent long-term stability in SOIC and MSOP footprints. Patented temperature drift curvature correction technique and XFET technology minimize nonlinearity of the voltage change with temperature. The XFET architecture offers superior accuracy and thermal hysteresis to the band gap references. It also operates at lower power and lower supply headroom than the buried Zener references. APPLICATIONS Precision data acquisition systems High resolution converters Battery-powered instrumentation Portable medical instruments Industrial process control systems Precision instruments Optical network control circuits The superb noise and the stable and accurate characteristics of the ADR42x make them ideal for precision conversion applications such as optical networks and medical equipment. The ADR42x trim terminal can also be used to adjust the output voltage over a 0.5% range without compromising any other performance. The ADR42x series voltage references offer two electrical grades and are specified over the extended industrial temperature range of -40C to +125C. Devices have 8-lead SOIC or 30% smaller, 8-lead MSOP packages. ADR42x PRODUCTS Table 1. Model ADR420 ADR421 ADR423 ADR425 Output Voltage (VO) 2.048 2.50 3.00 5.00 mV 1, 3 1, 3 1.5, 4 2, 6 Initial Accuracy % 0.05, 0.15 0.04, 0.12 0.04, 0.13 0.04, 0.12 Temperature Coefficient (ppm/C) 3, 10 3, 10 3, 10 3, 10 Rev. G 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 that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c) 2005 Analog Devices, Inc. All rights reserved. ADR420/ADR421/ADR423/ADR425 TABLE OF CONTENTS Features .............................................................................................. 1 Applications....................................................................................... 1 Pin Configuration............................................................................. 1 General Description ......................................................................... 1 ADR420 Electrical Specifications................................................... 3 ADR421 Electrical Specifications................................................... 4 ADR423 Electrical Specifications................................................... 5 ADR425 Electrical Specifications................................................... 6 Absolute Maximum Ratings............................................................ 7 ESD Caution.................................................................................. 7 Pin Configuration and Function Descriptions............................. 8 Typical Performance Characteristics ............................................. 9 Parameter Definitions .................................................................... 15 Theory of Operation ...................................................................... 16 Device Power Dissipation Considerations.............................. 16 Basic Voltage Reference Connections...................................... 16 Noise Performance ..................................................................... 16 Turn-On Time ............................................................................ 16 Applications..................................................................................... 17 Output Adjustment .................................................................... 17 Reference for Converters in Optical Network Control Circuits.......................................................................... 17 A Negative Precision Reference Without Precision Resistors...................................................... 17 High Voltage Floating Current Source .................................... 18 Kelvin Connections.................................................................... 18 Dual-Polarity References........................................................... 18 Programmable Current Source ................................................ 19 Programmable DAC Reference Voltage .................................. 19 Precision Voltage Reference for Data Converters.................. 20 Precision Boosted Output Regulator ....................................... 20 Outline Dimensions ....................................................................... 21 Ordering Guide .......................................................................... 22 REVISION HISTORY 6/05--Rev. F to Rev. G Changes to Table 1............................................................................ 1 Changes to Ordering Guide .......................................................... 22 2/05--Rev. E to Rev. F Updated Format..................................................................Universal Updated Outline Dimensions ....................................................... 21 Changes to Ordering Guide .......................................................... 22 7/04--Rev. D to Rev. E. Changes to Ordering Guide ............................................................ 5 3/04--Rev. C to Rev. D. Changes to Table I ............................................................................ 1 Changes to Ordering Guide ............................................................ 4 Updated Outline Dimensions ....................................................... 16 1/03--Rev. B to Rev. C. Changed Mini_SOIC to MSOP ........................................Universal Changes to Ordering Guide .............................................................4 Corrections to Y-axis labels in TPCs 21 and 24 ............................9 Enhancement to Figure 13 ............................................................ 15 Updated Outline Dimensions....................................................... 16 3/02--Rev. A to Rev. B. Edits to Ordering Guide ...................................................................4 Deletion of Precision Voltage Regulator section........................ 15 Addition of Precision Boosted Output Regulator section ....... 15 Addition of Figure 13..................................................................... 15 Rev. 0 to Rev. A. Addition of ADR423 and ADR425 to ADR420/ADR421...............................................................Universal Rev. G | Page 2 of 24 ADR420/ADR421/ADR423/ADR425 ADR420 ELECTRICAL SPECIFICATIONS @ VIN = 5.0 V to 15.0 V, TA = 25C, unless otherwise noted. Table 2. Parameter Output Voltage, A Grade Initial Accuracy Symbol VO VOERR Output Voltage, B Grade Initial Accuracy VO VOERR Temperature Coefficient A Grade, Temperature Coefficient, B Grade Supply Voltage Headroom Line Regulation TCVO -40C < TA < +125C VIN - VO VO/VIN VIN = 5 V to 18 V VO/ILOAD -40C < TA < +125C ILOAD = 0 mA to 10 mA Load Regulation Quiescent Current IIN Voltage Noise Voltage Noise Density Turn-On Settling Time Long-Term Stability Output Voltage Hysteresis Ripple Rejection Ratio Short Circuit to GND eN p-p eN tR VO VO_HYS RRR ISC Conditions Min 2.045 -3 -0.15 2.047 -1 -0.05 Typ 2.048 2 1 Max 2.051 +3 +0.15 2.049 +1 +0.05 10 3 10 35 Unit V mV % V mV % ppmC ppm/C V ppm/V 70 ppm/mA 500 600 A A V p-p nV/Hz s ppm ppm dB mA 2.048 2 -40C < TA < +125C No load -40C < TA < +125C 0.1 Hz to 10 Hz 1 kHz 1,000 hours fIN = 10 kHz Rev. G | Page 3 of 24 390 1.75 60 10 50 40 75 27 ADR420/ADR421/ADR423/ADR425 ADR421 ELECTRICAL SPECIFICATIONS @ VIN = 5.0 V to 15.0 V, TA = 25C, unless otherwise noted. Table 3. Parameter Output Voltage, A Grade Initial Accuracy Symbol VO VOERR Conditions Output Voltage, B Grade Initial Accuracy VO VOERR Temperature Coefficient, A Grade Temperature Coefficient, B Grade Supply Voltage Headroom Line Regulation TCVO -40C < TA < +125C VIN - VO VO/VIN VIN = 5 V to 18 V Load Regulation VO/ILOAD -40C < TA < +125C ILOAD = 0 mA to 10 mA Quiescent Current IIN Voltage Noise Voltage Noise Density Turn-On Settling Time Long-Term Stability Output Voltage Hysteresis Ripple Rejection Ratio Short Circuit to GND eN p-p eN tR VO VO_HYS RRR ISC Min 2.497 -3 -0.12 2.499 -1 -0.04 Typ 2.500 2 1 Max 2.503 +3 +0.12 2.501 +1 +0.04 10 3 10 35 Unit V mV % V mV % ppm/C ppm/C V ppm/V 70 ppm/mA 500 600 A A V p-p nV/Hz s ppm ppm dB mA 2.500 2 -40C < TA < +125C No load -40C < TA < +125C 0.1 Hz to 10 Hz 1 kHz 1,000 hours fIN = 10 kHz Rev. G | Page 4 of 24 390 1.75 80 10 50 40 75 27 ADR420/ADR421/ADR423/ADR425 ADR423 ELECTRICAL SPECIFICATIONS @ VIN = 5.0 V to 15.0 V, TA = 25C, unless otherwise noted. Table 4. Parameter Output Voltage, A Grade Initial Accuracy Symbol VO VOERR Conditions Output Voltage, B Grade Initial Accuracy VO VOERR Temperature Coefficient, A Grade Temperature Coefficient, B Grade Supply Voltage Headroom Line Regulation TCVO -40C < TA < +125C VIN - VO VO/VIN VIN = 5 V to 18 V Load Regulation VO/ILOAD -40C < TA < +125C ILOAD = 0 mA to 10 mA Quiescent Current IIN Voltage Noise Voltage Noise Density Turn-On Settling Time Long-Term Stability Output Voltage Hysteresis Ripple Rejection Ratio Short Circuit to GND eN p-p eN tR VO VO_HYS RRR ISC Min 2.996 -4 -0.13 2.9985 -1.5 -0.04 Typ 3.000 2 1 Max 3.004 +4 +0.13 3.0015 +1.5 +0.04 10 3 10 35 Unit V mV % V mV % ppm/C ppm/C V ppm/V 70 ppm/mA 500 600 A A V p-p nV/Hz s ppm ppm dB mA 3.000 2 -40C < TA < +125C No load -40C < TA < +125C 0.1 Hz to 10 Hz 1 kHz 1,000 hours fIN = 10 kHz Rev. G | Page 5 of 24 390 2 90 10 50 40 75 27 ADR420/ADR421/ADR423/ADR425 ADR425 ELECTRICAL SPECIFICATIONS @ VIN = 7.0 V to 15.0 V, TA = 25C, unless otherwise noted. Table 5. Parameter Output Voltage, A Grade Initial Accuracy Symbol VO VOERR Output Voltage, B Grade Initial Accuracy VO VOERR Temperature Coefficient, A Grade Temperature Coefficient, B Grade Supply Voltage Headroom Line Regulation TCVO VIN - VO VO/VIN Load Regulation VO/ILOAD Quiescent Current IIN Voltage Noise Voltage Noise Density Turn-On Settling Time Long-Term Stability Output Voltage Hysteresis Ripple Rejection Ratio Short Circuit to GND eN p-p eN tR VO VO_HYS RRR ISC Conditions Min 4.994 -6 -0.12 4.998 -2 -0.04 -40C < TA < +125C Typ 5.000 2 1 Max 5.006 +6 +0.12 5.002 +2 +0.04 10 3 10 35 Unit V mV % V mV % ppm/C ppm/C V ppm/V 70 ppm/mA 500 600 A A V p-p nV/Hz s ppm ppm dB mA 5.000 2 VIN = 7 V to 18 V -40C < TA < +125C ILOAD = 0 mA to 10 mA -40C < TA < +125C No load -40C < TA < +125C 0.1 Hz to 10 Hz 1 kHz 1,000 hours fIN = 10 kHz Rev. G | Page 6 of 24 390 3.4 110 10 50 40 75 27 ADR420/ADR421/ADR423/ADR425 ABSOLUTE MAXIMUM RATINGS These ratings apply at 25C, unless otherwise noted. Table 6. Parameter Supply Voltage Output Short-Circuit Duration to GND Storage Temperature Range R, RM Packages Operating Temperature Range ADR42x Junction Temperature Range R, RM Packages Lead Temperature (Soldering, 60 sec) Rating 18 V Indefinite -65C to +150C -40C to +125C -65C to +150C 300C 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 indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 7. Package Type JA 1 Unit 8-Lead MSOP (RM) 8-Lead SOIC (R) 190 130 C/W C/W 1 JA is specified for the worst-case conditions, that is, JA is specified for devices soldered in the circuit board for surface-mount packages. ESD 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 this product 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. Rev. G | Page 7 of 24 ADR420/ADR421/ADR423/ADR425 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS GND 4 8 TP TP 1 7 NIC VIN 2 6 VOUT NIC 3 TOP VIEW (Not to Scale) 5 TRIM NIC = NO INTERNAL CONNECTION TP = TEST PIN (DO NOT CONNECT) GND 4 ADR420/ ADR421/ ADR423/ ADR425 8 TP 7 NIC VOUT TOP VIEW 5 TRIM (Not to Scale) 6 NIC = NO INTERNAL CONNECTION TP = TEST PIN (DO NOT CONNECT) Figure 2. Pin Configuration for 8-Lead SOIC 02432-003 NIC 3 ADR420/ ADR421/ ADR423/ ADR425 02432-002 TP 1 VIN 2 Figure 3. Pin Configuration for 8-Lead MSOP Table 8. Pin Function Descriptions Pin No. 1, 8 Mnemonic TP 2 3, 7 4 5 VIN NIC GND TRIM 6 VOUT Description Test Pin. There are actual connections in TP pins but they are reserved for factory testing purposes. Users should not connect anything to TP pins; otherwise, the device may not function properly. Input Voltage. No Internal Connect. NICs have no internal connections. Ground Pin = 0 V. Trim Terminal. It can be used to adjust the output voltage over a 0.5% range without affecting the temperature coefficient. Output Voltage. Rev. G | Page 8 of 24 ADR420/ADR421/ADR423/ADR425 5.0025 2.0493 5.0023 2.0491 5.0021 2.0489 5.0019 2.0487 5.0017 2.0485 2.0483 5.0015 5.0013 2.0481 5.0011 2.0479 5.0009 2.0477 2.0475 -40 -10 20 50 TEMPERATURE (C) 80 110 02432-007 VOUT (V) 2.0495 02432-004 VOUT (V) TYPICAL PERFORMANCE CHARACTERISTICS 5.0007 5.0005 -40 125 Figure 4. ADR420 Typical Output Voltage vs. Temperature -10 20 50 TEMPERATURE (C) 80 110 125 Figure 7. ADR425 Typical Output Voltage vs. Temperature 0.55 2.5015 2.5013 0.50 SUPPLY CURRENT (mA) 2.5011 2.5007 2.5005 2.5003 2.5001 2.4999 +25C 0.40 -40C 0.35 02432-005 0.30 2.4997 2.4995 -40 +125C 0.45 -10 20 50 TEMPERATURE (C) 80 110 02432-008 VOUT (V) 2.5009 0.25 4 125 6 8 10 INPUT VOLTAGE (V) 12 14 15 Figure 8. ADR420 Supply Current vs. Input Voltage Figure 5. ADR421 Typical Output Voltage vs. Temperature 0.55 3.0010 3.0008 0.50 SUPPLY CURRENT (mA) 3.0006 3.0002 3.0000 2.9998 2.9996 2.9994 +125C 0.40 +25C 0.35 -40C -10 20 50 TEMPERATURE (C) 80 110 02432-009 2.9992 2.9990 -40 0.45 0.30 02432-006 VOUT (V) 3.0004 0.25 4 125 6 8 10 INPUT VOLTAGE (V) 12 14 Figure 9. ADR421 Supply Current vs. Input Voltage Figure 6. ADR423 Typical Output Voltage vs. Temperature Rev. G | Page 9 of 24 15 ADR420/ADR421/ADR423/ADR425 0.55 70 IL = 0mA TO 5mA 60 LOAD REGULATION (ppm/mA) 0.50 0.40 +25C 0.35 -40C 0.30 4 6 8 10 INPUT VOLTAGE (V) 12 14 VIN = 5V 40 30 VIN = 6.5V 20 10 02432-010 0.25 50 0 -40 15 Figure 10. ADR423 Supply Current vs. Input Voltage 02432-013 SUPPLY CURRENT (mA) +125C 0.45 -10 20 50 TEMPERATURE (C) 80 110 125 Figure 13. ADR421 Load Regulation vs. Temperature 0.55 70 0.50 60 LOAD REGULATION (ppm/mA) +125C 0.45 0.40 +25C 0.35 -40C 0.30 6 8 10 12 INPUT VOLTAGE (V) 14 VIN = 7V 40 30 VIN = 15V 20 0 -40 15 Figure 11. ADR425 Supply Current vs. Input Voltage -10 20 50 TEMPERATURE (C) 80 110 125 Figure 14. ADR423 Load Regulation vs. Temperature 70 35 VIN = 15V IL = 0mA TO 10mA IL = 0mA TO 5mA 60 LOAD REGULATION (ppm/mA) 30 50 40 VIN = 6V 30 VIN = 4.5V 20 10 0 -40 -10 20 50 TEMPERATURE (C) 80 110 25 20 15 10 5 02432-012 LOAD REGULATION (ppm/mA) 02432-014 10 02432-011 0.25 50 0 -40 125 Figure 12. ADR420 Load Regulation vs. Temperature 02432-015 SUPPLY CURRENT (mA) IL = 0mA TO 10mA -10 20 50 TEMPERATURE (C) 80 110 125 Figure 15. ADR425 Load Regulation vs. Temperature Rev. G | Page 10 of 24 ADR420/ADR421/ADR423/ADR425 6 14 VIN = 4.5V TO 15V VIN = 7.5V TO 15V 12 LINE REGULATION (ppm/V) 4 3 2 1 -10 20 50 TEMPERATURE (C) 80 8 6 4 2 02432-016 0 -40 10 02432-019 LINE REGULATION (ppm/V) 5 0 -40 110 125 Figure 16. ADR420 Line Regulation vs. Temperature -10 20 50 TEMPERATURE (C) 80 110 125 Figure 19. ADR425 Line Regulation vs. Temperature 2.5 6 VIN = 5V TO 15V 4 3 2 0 -40 02432-017 1 -10 20 50 TEMPERATURE (C) 80 110 2.0 -40C +25C 1.5 +85C 1.0 0.5 02432-020 DIFFERENTIAL VOLTAGE (V) LINE REGULATION (ppm/V) 5 0 0 125 1 2 3 LOAD CURRENT (mA) 4 5 Figure 20. ADR420 Minimum Input/Output Voltage Differential vs. Load Current Figure 17. ADR421 Line Regulation vs. Temperature 2.5 9 VIN = 5V TO 15V 6 5 4 3 2 1 0 -40 -10 20 50 TEMPERATURE (C) 80 2.0 -40C +25C 1.5 +125C 1.0 0.5 02432-021 DIFFERENTIAL VOLTAGE (V) 7 02432-018 LINE REGULATION (ppm/V) 8 0 0 110 1 2 3 LOAD CURRENT (mA) 4 Figure 21. ADR421 Minimum Input/Output Voltage Differential vs. Load Current Figure 18. ADR423 Line Regulation vs. Temperature Rev. G | Page 11 of 24 5 ADR420/ADR421/ADR423/ADR425 2.0 -40C 1.5 1V/DIV +25C +125C 1.0 02432-025 0.5 02432-022 DIFFERENTIAL VOLTAGE (V) 2.5 0 0 1 2 3 LOAD CURRENT (mA) 4 TIME (1s/DIV) 5 Figure 22. ADR423 Minimum Input/Output Voltage Differential vs. Load Current Figure 25. ADR421 Typical Noise Voltage 0.1 Hz to 10 Hz 2.0 -40C +25C 50V/DIV 1.5 +125C 1.0 02432-026 0.5 02432-023 0 0 1 2 3 LOAD CURRENT (mA) 4 TIME (1s/DIV) 5 Figure 23. ADR425 Minimum Input/Output Voltage Differential vs. Load Current 1k TEMPERATURE +25C -40C +125C +25C SAMPLE SIZE - 160 VOLTAGE NOISE DENSITY (nV/ Hz) 30 Figure 26. Typical Noise Voltage 10 Hz to 10 kHz 20 15 10 DEVIATION (ppm) ADR425 ADR423 100 ADR420 10 10 70 80 90 100 110 120 130 MORE 20 30 40 50 60 0 02432-024 5 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 NUMBER OF PARTS 25 ADR421 02432-027 DIFFERENTIAL VOLTAGE (V) 2.5 100 1k FREQUENCY (Hz) Figure 27. Voltage Noise Density vs. Frequency Figure 24. ADR421 Typical Hysteresis Rev. G | Page 12 of 24 10k ADR420/ADR421/ADR423/ADR425 CL = 100nF CBYPASS = 0F 1mA LOAD LINE INTERRUPTION VOUT VIN 500mV/DIV VOUT 500mV/DIV 1V/DIV LOAD OFF 2V/DIV 02432-031 02432-028 LOAD ON TIME (100s/DIV) TIME (100s/DIV) Figure 28. ADR421 Line Transient Response, no CBYPASS Figure 31. ADR421 Load Transient Response, CL = 100 nF CIN = 0.01F NO LOAD CBYPASS = 0.1F LINE INTERRUPTION VIN 500mV/DIV VOUT 500mV/DIV VOUT 2V/DIV 02432-032 02432-029 VIN 2V/DIV TIME (100s/DIV) TIME (4s/DIV) Figure 29. ADR421 Line Transient Response, CBYPASS = 0.1 F CL = 0F Figure 32. ADR421 Turn-Off Response CIN = 0.01F NO LOAD 1mA LOAD VOUT 2V/DIV VOUT 1V/DIV LOAD OFF VIN 2V/DIV 2V/DIV 02432-030 02432-033 LOAD ON TIME (4s/DIV) TIME (100s/DIV) Figure 33. ADR421 Turn-On Response Figure 30. ADR421 Load Transient Response, no CL Rev. G | Page 13 of 24 ADR420/ADR421/ADR423/ADR425 50 CLOAD = 0.01F NO INPUT CAP 45 OUTPUT IMPEDANCE () 40 VOUT 2V/DIV VIN 2V/DIV 35 30 ADR425 25 ADR423 20 ADR421 15 5 ADR420 0 10 TIME (4s/DIV) 100 1k FREQUENCY (Hz) 10k 02432-037 02432-034 10 100k Figure 37. Output Impedance vs. Frequency Figure 34. ADR421 Turn-Off Response 0 CLOAD = 0.01F NO INPUT CAP -10 VOUT 2V/DIV RIPPLE REJECTION (dB) -20 VIN 2V/DIV -30 -40 -50 -60 -70 -90 -100 10 TIME (4s/DIV) CBYPASS = 0.1F RL = 500 CL = 0 VIN 2V/DIV 02432-036 5V/DIV 100 1k 10k FREQUENCY (Hz) 100k Figure 38. Ripple Rejection vs. Frequency Figure 35. ADR421 Turn-On Response VOUT 02432-038 02432-035 -80 TIME (100s/DIV) Figure 36. ADR421 Turn-On/Turn-Off Response Rev. G | Page 14 of 24 1M ADR420/ADR421/ADR423/ADR425 PARAMETER DEFINITIONS Temperature Coefficient The change of output voltage over the operating temperature range is normalized by the output voltage at 25C, and expressed in ppm/C as TCVO ( ppm / C ) = VO (T2 ) - VO (T1 ) x 106 VO (25C ) x (T2 - T1 ) VO _ HYS = VO (25C ) - VO _ TC where: VO (25C) = VO at 25C. VO (T1) = VO at Temperature 1. VO (T2) = VO at Temperature 2. VO _ HYS ( ppm) = Line Regulation The change in output voltage due to a specified change in input voltage. It includes the effects of self-heating. Line regulation is expressed in either percent-per-volt, parts-per-million per volt, or microvolts-per-volt change in input voltage. Load Regulation The change in output voltage due to a specified change in load current. It includes the effects of self-heating. Load regulation is expressed in either microvolts-per-milliampere, parts-permillion per milliampere, or ohms of dc output resistance. Long-Term Stability Typical shift of output voltage at 25C on a sample of parts subjected to operation life test of 1,000 of hours at 125C VO = VO (t 0 ) - VO (t1 ) VO ( ppm ) = VO (t 0 ) - VO (t1 ) x 106 VO (t 0 ) where: VO (t0) = VO at 25C at Time 0. VO (t1) = VO at 25C after 1,000 hours operation at 125C. Thermal Hysteresis The change of output voltage after the device is cycled through temperatures from +25C to -40C to +125C and back to +25C. This is a typical value from a sample of parts put through such a cycle VO (25C ) - VO _ TC VO (25C ) x 106 where: VO (25C) = VO at 25C. VO_TC = VO at 25 C after temperature cycle at +25C to -40C to +125C and back to +25C. Input Capacitor Input capacitors are not required on the ADR42x. There is no limit for the value of the capacitor used on the input, but a 1 F to 10 F capacitor on the input improves transient response in applications where the supply suddenly changes. An additional 0.1 F capacitor in parallel also helps to reduce noise from the supply. Output Capacitor The ADR42x do not need output capacitors for stability under any load condition. An output capacitor, typically 0.1 F, filters out any low level noise voltage and does not affect the operation of the part. On the other hand, the load transient response can be improved with an additional 1 F to 10 F output capacitor in parallel. A capacitor here acts as a source of stored energy for sudden increase in load current. The only parameter that degrades by adding an output capacitor is the turn-on time, and it depends on the size of the selected capacitor. Rev. G | Page 15 of 24 ADR420/ADR421/ADR423/ADR425 THEORY OF OPERATION The intrinsic reference voltage is about 0.5 V with a negative temperature coefficient of about -120 ppm/C. This slope is essentially constant 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 band gap references. The primary advantage over a band gap reference is that the intrinsic temperature coefficient is approximately 30 times lower (therefore requiring less correction). This results in much lower noise because most of the noise of a band gap reference comes from the temperature compensation circuitry. Figure 39 shows the basic topology of the ADR42x series. The temperature correction term is provided by a current source with a value designed to be proportional to absolute temperature. The general equation is VOUT = G x (VP - R1 x IPTAT) ADR42x are created by on-chip adjustment of R2 and R3 to achieve 2.048 V or 2.500 V at the reference output, respectively. VIN I1 ADR420/ADR421/ ADR423/ADR425 IPTAT VOUT R2 * R1 *EXTRA CHANNEL IMPLANT VOUT = G(VP - R1 x IPTAT) Figure 39. Simplified Schematic R3 GND 02432-039 VP The ADR42x family of references is guaranteed to deliver load currents to 10 mA with an input voltage that ranges from 4.5 V to 18 V. When these devices are used in applications at higher currents, the following equation should be used to account for the temperature effects due to power dissipation increases: TJ = PD x JA + TA (2) where: TJ and TA are the junction and ambient temperatures, respectively. PD is the device power dissipation. JA is the device package thermal resistance. BASIC VOLTAGE REFERENCE CONNECTIONS Voltage references, in general, require a bypass capacitor connected from VOUT to GND. The circuit in Figure 40 illustrates the basic configuration for the ADR42x family of references. Other than a 0.1 F capacitor at the output to help improve noise suppression, a large output capacitor at the output is not required for circuit stability. TP 1 VIN 10F + 2 0.1F (1) where: G is the gain of the reciprocal of the divider ratio. VP is the difference in pinch-off voltage between the two JFETs. IPTAT is the positive temperature coefficient correction current. I1 DEVICE POWER DISSIPATION CONSIDERATIONS NIC 3 4 ADR420/ ADR421/ ADR423/ ADR425 8 TP 7 NIC OUTPUT 6 TOP VIEW (Not to Scale) 5 TRIM NIC = NO INTERNAL CONNECTION TP = TEST PIN (DO NOT CONNECT) 0.1F 02432-040 The ADR42x series of references uses a new reference generation technique known as XFET (eXtra implanted junction FET). This technique yields a reference with low supply current, good thermal hysteresis, and exceptionally low noise. The core of the XFET reference consists of two junction field-effect transistors (JFET), one having an extra channel implant to raise its pinchoff 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. Figure 40. Basic Voltage Reference Configuration NOISE PERFORMANCE The noise generated by ADR42x references is typically less than 2 V p-p over the 0.1 Hz to 10 Hz band for the ADR420, ADR421, and ADR423. Figure 25 shows the 0.1 Hz to 10 Hz noise of the ADR421, which is only 1.75 V p-p. The noise measurement is made with a band-pass 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 At power-up (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 typically 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 32 to Figure 36 show the turn-on settling time for the ADR421. Rev. G | Page 16 of 24 ADR420/ADR421/ADR423/ADR425 APPLICATIONS OUTPUT ADJUSTMENT SOURCE FIBER GIMBAL + SENSOR DESTINATION FIBER LASER BEAM MEMS MIRROR ACTIVATOR LEFT AMPL PREAMP ACTIVATOR RIGHT AMPL ADR421 CONTROL ELECTRONICS ADR421 DAC ADC DAC INPUT DSP 2 ADR420/ ADR421/ ADR423/ ADR425 GND 4 OUTPUT VO = 0.5% VO 6 R1 470k TRIM 5 R2 RP 10k 10k (ADR420) 15k (ADR421) Figure 42. All-Optical Router Network A NEGATIVE PRECISION REFERENCE WITHOUT PRECISION RESISTORS 02432-041 VIN ADR421 02432-042 The ADR42x trim terminal can be used to adjust the output voltage over a 0.5% range. This feature allows the system designer to trim system errors out by setting the reference to a voltage other than the nominal. This is also helpful if the part is used in a system at temperature to trim out any error. Adjustment of the output has a negligible effect on the temperature performance of the device. To avoid degrading temperature coefficients, both the trimming potentiometer and the two resistors need to be low temperature coefficient types, preferably <100 ppm/C. Figure 41. Output Trim Adjustment REFERENCE FOR CONVERTERS IN OPTICAL NETWORK CONTROL CIRCUITS In the high capacity, all-optical router network of Figure 42, arrays of micromirrors direct and route optical signals from fiber to fiber, without first converting them to electrical form, which reduces the communication speed. The tiny micromechanical mirrors are positioned so that each is illuminated by a single wave length that carries unique information and can be passed to any desired input and output fiber. The mirrors are tilted by the dual-axis actuators controlled by precision analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) within the system. Due to the microscopic movement of the mirrors, not only is the precision of the converters important, but the noise associated with these controlling converters is extremely critical, because total noise within the system can be multiplied by the numbers of converters used. Consequently, the exceptional low noise of the ADR42x is necessary to maintain the stability of the control loop for this application. In many current-output CMOS DAC applications where the output signal voltage must be of the same polarity as the reference voltage, a current-switching DAC is often reconfigured into a voltage-switching DAC with a 1.25 V reference, an op amp, a pair of resistors, and an additional operational amplifier at the output to reinvert the signal. A negative voltage reference should be used because an additional operational amplifier is not required for either reinversion (currentswitching 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 this approach is that the largest single source of error in the circuit is the relative matching of the resistors used. A negative reference can easily be generated by adding a precision op amp and configuring as shown in Figure 43. VOUT is at virtual ground and, therefore, the negative reference can be taken directly from the output of the op amp. The op amp must be dual-supply, low offset and have rail-to-rail capability if negative supply voltage is close to the reference output. Rev. G | Page 17 of 24 ADR420/ADR421/ADR423/ADR425 +VDD VIN 2 2 VOUT VIN RLW A1 VOUT 6 GND GND 4 A1 = OP191 -VREF Figure 45. Advantage of Kelvin Connection 02432-043 A1 = OP777, OP193 -VDD VOUT FORCE RL 4 A1 VOUT SENSE DUAL-POLARITY REFERENCES Figure 43. Negative Reference HIGH VOLTAGE FLOATING CURRENT SOURCE The circuit in Figure 44 can be used to generate a floating current source with minimal self-heating. This particular configuration can operate on high supply voltages determined by the breakdown voltage of the N-channel JFET. Dual-polarity references can easily be made with an op amp and a pair of resistors. In order not to defeat the accuracy obtained by the ADR42x, it is imperative to match the resistance tolerance and the temperature coefficient of all components. VIN 1F 0.1F 2 VIN VOUT 6 U1 SST111 VISHAY +5V R1 10k +VS ADR425 2 GND VIN 4 R2 10k +10V V+ TRIM 5 U2 OP1177 ADR420/ ADR421/ ADR423/ ADR425 -5V 02432-046 6 RLW ADR420/ ADR421/ ADR423/ ADR425 02432-045 VIN ADR420/ ADR421/ ADR423/ ADR425 V- R3 5k VOUT 6 OP09 -10V Figure 46. +5 V and -5 V Reference Using ADR425 2N3904 GND +2.5V 4 RL 2.10k 02432-044 2 VIN VOUT 6 U1 Figure 44. High Voltage Floating Current Source ADR425 GND KELVIN CONNECTIONS 4 In many portable instrumentation applications where PC board cost and area are important considerations, circuit interconnects are often narrow. 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 m/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 x IL) at the load. However, the Kelvin connection in Figure 45 overcomes the problem by including the wiring resistance within the forcing loop of the op amp. Because 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. Rev. G | Page 18 of 24 R1 5.6k TRIM 5 R2 5.6k V+ U2 OP1177 -2.5V V- -10V 02432-047 -VS +10V Figure 47. +2.5 V and -2.5 V Reference Using ADR425 ADR420/ADR421/ADR423/ADR425 PROGRAMMABLE CURRENT SOURCE PROGRAMMABLE DAC REFERENCE VOLTAGE Together with a digital potentiometer and a Howland current pump, the ADR425 forms the reference source for a programmable current as With a multichannel DAC, such as the quad, 12-bit voltage output AD7398, one of its internal DACs, and an ADR42x voltage reference can be used as a common programmable VREFX for the rest of the DACs. The circuit configuration is shown in Figure 49. The relationship of VREFX to VREF depends on the digital code and the ratio of R1 and R, and is given by R2A + R2B R1 IL = R2B xV (3) W and VREFX D VW = N x VREF 2 (4) C1 10pF R1' 50k 2 R1, R2 R1 = R2 R1 = R2 R1 = R2 R1 = 3R2 R1 = 3R2 R1 = 3R2 VDD AD5232 U2 DIGITAL POT VDD VOUT 6 C2 10pF V- A U2 B W V+ A2 OP2177 V+ A1 OP2177 V- VSS R2B 10 VSS R1 50k Digital Code 0000 0000 0000 1000 0000 0000 1111 1111 1111 0000 0000 0000 1000 0000 0000 1111 1111 1111 VREF 2 VREF 1.3 VREF VREF 4 VREF 1.6 VREF VREF R2A 1k VL LOAD IL Figure 48. Programmable Current Source VREFA VOUTA R1 0.1% VREF DACA R1' and R2' must be equal to R1 and R2A + R2B, respectively. Theoretically, R2B can be made as small as needed to achieve the current needed within A2 output current driving capability. In the example shown in Figure 48, OP2177 is able to deliver a maximum of 10 mA. Because the current pump uses both positive and negative feedback, Capacitors C1 and C2 are needed to ensure that negative feedback prevails and, therefore, avoids oscillation. This circuit also allows bidirectional current flow if the inputs VA and VB of the digital potentiometer are supplied with the dual-polarity references as previously shown. R2 0.1% VIN ADR425 B B B VREFB VOUTB VOB = VREFX (DB) DACB VREFC VOUTC VOC = VREFX (DC) DACC VREFD VOUTD VOD = VREFX (DD) DACD AD7398 Figure 49. Programmable DAC Reference Rev. G | Page 19 of 24 02432-049 U1 4 Table 9. VREFX vs. R1 and R2 TRIM 5 ADR425 GND R2' 1k 02432-048 VIN (5) where: D = Decimal equivalent of input code. N = Number of bits. VREF = Applied external reference. VREFX = Reference voltage for DACs A to D. where: D = Decimal equivalent of the input code. N = Number of bits. VDD R2 VREF x 1 + R1 = 1 + D x R2 2N R1 ADR420/ADR421/ADR423/ADR425 PRECISION BOOSTED OUTPUT REGULATOR The ADR42x family has a number of features that make it ideal for use with ADCs and DACs. The exceptionally low noise, tight temperature coefficient, and high accuracy characteristics make the ADR42x ideal for low noise applications such as cellular base station applications. AD7701 is an example of an ADC that is well suited for the ADR42x. The ADR421 is used as the precision reference for the converter in Figure 50. The AD7701 is a 16-bit ADC with on-chip digital filtering intended for measuring wide dynamic range and low frequency signals, such as those representing chemical, physical, or biological processes. It contains a chargebalancing (-) ADC, calibration microcontroller with on-chip static RAM, clock oscillator, and serial communications port. A precision voltage output with boosted current capability can be realized with the circuit shown in Figure 51. In this circuit, U2 forces VO to be equal to VREF by regulating the turn on of N1. Therefore, the load current is furnished by VIN. In this configuration, a 50 mA load is achievable at VIN of 5 V. Moderate heat is generated on the MOSFET, and higher current can be achieved by replacing the larger device. In addition, for a heavy capacitive load with step input, a buffer may be added at the output to enhance the transient response. N1 VIN 2 U1 VIN VOUT 6 ADR421 +5V ANALOG SUPPLY 0.1F 10F TRIM GND 4 AD7701 AVDD VOUT 0.1F VREF CS GND DATA READY READ (TRANSMIT) SCLK SERIAL CLOCK SDATA SERIAL CLOCK CLKIN BP/UP CAL CALIBRATE ANALOG INPUT ANALOG GROUND AIN AGND 0.1F AVSS -5V ANALOG SUPPLY 0.1F CLKOUT SC1 SC2 DGND 0.1F DVSS 10F 02432-050 RANGES SELECT 2N7002 AD8601 - V- Figure 51. Precision Boosted Output Regulator 0.1F MODE DRDV ADR420/ ADR421/ ADR423/ ADR425 5 Figure 50. Voltage Reference for 16-Bit ADC AD7701 Rev. G | Page 20 of 24 VO + V+ U2 DVDD SLEEP VIN RL 25 5V 02432-051 PRECISION VOLTAGE REFERENCE FOR DATA CONVERTERS ADR420/ADR421/ADR423/ADR425 OUTLINE DIMENSIONS 5.00 (0.1968) 4.80 (0.1890) 8 5 4.00 (0.1574) 3.80 (0.1497) 1 6.20 (0.2440) 4 5.80 (0.2284) 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) 0.50 (0.0196) x 45 0.25 (0.0099) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE 8 0.25 (0.0098) 0 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067) COMPLIANT TO JEDEC STANDARDS MS-012-AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN Figure 52. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) 3.00 BSC 8 3.00 BSC 1 5 4.90 BSC 4 PIN 1 0.65 BSC 1.10 MAX 0.15 0.00 0.38 0.22 COPLANARITY 0.10 0.23 0.08 8 0 SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 53. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters Rev. G | Page 21 of 24 0.80 0.60 0.40 ADR420/ADR421/ADR423/ADR425 ORDERING GUIDE Temp Model ADR420AR ADR420AR-REEL7 ADR420ARZ 1 ADR420ARZ-REEL71 ADR420ARM ADR420ARM-REEL7 ADR420ARMZ1 ADR420ARMZ-REEL71 ADR420BR ADR420BR-REEL7 ADR420BRZ1 ADR420BRZ-REEL71 ADR421AR ADR421AR-REEL7 ADR421ARZ1 ADR421ARZ-REEL71 ADR421ARM ADR421ARM-REEL7 ADR421ARMZ1 ADR421ARMZ-REEL71 ADR421BR ADR421BR-REEL7 ADR421BRZ1 ADR421BRZ-REEL71 ADR423AR ADR423AR-REEL7 ADR423ARZ1 ADR423ARZ-REEL71 ADR423ARM ADR423ARM-REEL7 ADR423BR ADR423BR-REEL7 ADR423ARMZ1 ADR423ARMZ-REEL71 ADR423BRZ1 ADR423BRZ-REEL71 ADR425AR ADR425AR-REEL7 ADR425ARZ1 ADR425ARZ-REEL71 ADR425ARM ADR425ARM-REEL7 ADR425ARMZ1 ADR425ARMZ-REEL71 ADR425BR ADR425BR-REEL7 ADR425BRZ1 ADR425BRZ-REEL71 1 Range (C) -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 -40 to +125 Package Description SOIC_N SOIC_N SOIC_N SOIC_N MSOP MSOP MSOP MSOP SOIC_N SOIC_N SOIC_N SOIC_N SOIC_N SOIC_N SOIC_N SOIC_N MSOP MSOP MSOP MSOP SOIC_N SOIC_N SOIC_N SOIC_N SOIC_N SOIC_N SOIC_N SOIC_N MSOP MSOP SOIC_N SOIC_N MSOP MSOP SOIC_N SOIC_N SOIC_N SOIC_N SOIC_N SOIC_N MSOP MSOP MSOP MSOP SOIC_N SOIC_N SOIC_N SOIC_N Package Option R-8 R-8 R-8 R-8 RM-8 RM-8 RM-8 RM-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 RM-8 RM-8 RM-8 RM-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 RM-8 RM-8 R-8 R-8 RM-8 RM-8 R-8 R-8 R-8 R-8 R-8 R-8 RM-8 RM-8 RM-8 RM-8 R-8 R-8 R-8 R-8 Top Mark ADR420 ADR420 ADR420 ADR420 R4A R4A L0C L0C ADR420 ADR420 ADR420 ADR420 ADR421 ADR421 ADR421 ADR421 R5A R5A R06 R06 ADR421 ADR421 ADR421 ADR421 ADR423 ADR423 ADR423 ADR423 R6A R6A ADR423 ADR423 R0U R0U ADR423 ADR423 ADR425 ADR425 ADR425 ADR425 R7A R7A R0V R0V ADR425 ADR425 ADR425 ADR425 Z = Pb-free part. Rev. G | Page 22 of 24 Output Voltage (VO) 2.048 2.048 2.048 2.048 2.048 2.048 2.048 2.048 2.048 2.048 2.048 2.048 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 Initial Accuracy mV % 3 0.15 3 0.15 3 0.15 3 0.15 3 0.15 3 0.15 3 0.15 3 0.15 1 0.05 1 0.05 1 0.05 1 0.05 3 0.12 3 0.12 3 0.12 3 0.12 3 0.12 3 0.12 3 0.12 3 0.12 1 0.04 1 0.04 1 0.04 1 0.04 4 0.13 4 0.13 4 0.13 4 0.13 4 0.13 4 0.13 1.5 0.04 1.5 0.04 4 0.13 4 0.13 1.5 0.04 1.5 0.04 6 0.12 6 0.12 6 0.12 6 0.12 6 0.12 6 0.12 6 0.12 6 0.12 2 0.04 2 0.04 2 0.04 2 0.04 Temp Co. (ppm/C) 10 10 10 10 10 10 10 10 3 3 3 3 10 10 10 10 10 10 10 10 3 3 3 3 10 10 10 10 10 10 3 3 10 10 3 3 10 10 10 10 10 10 10 10 3 3 3 3 ADR420/ADR421/ADR423/ADR425 NOTES Rev. G | Page 23 of 24 ADR420/ADR421/ADR423/ADR425 NOTES (c) 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C02432-0-6/05(G) Rev. G | Page 24 of 24