Ultraprecision, Low Noise, 2.048 V/2.500 V/ 3.00 V/5.00 V XFET® Voltage References ADR420/ADR421/ADR423/ADR425 FEATURES PIN CONFIGURATION Low noise (0.1 Hz to 10 Hz) ADR420: 1.75 μV p-p ADR421: 1.75 μV p-p ADR423: 2.0 μV p-p ADR425: 3.4 μV p-p Low temperature coefficient: 3 ppm/°C Long-term stability: 50 ppm/1000 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: −40°C to +125°C TP 1 VIN 2 ADR420/ ADR421/ ADR423/ ADR425 8 TP 7 NIC VOUT TOP VIEW GND 4 (Not to Scale) 5 TRIM 6 NIC = NO INTERNAL CONNECTION TP = TEST PIN (DO NOT CONNECT) 02432-001 NIC 3 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 −40°C to +125°C. Devices have 8-lead SOIC or 30% smaller, 8-lead MSOP packages. ADR42x PRODUCTS Table 1. Model ADR420 ADR421 ADR423 ADR425 Output Voltage, VOUT (V) 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. I 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 ©2001–2011 Analog Devices, Inc. All rights reserved. ADR420/ADR421/ADR423/ADR425 TABLE OF CONTENTS Features .............................................................................................. 1 Device Power Dissipation Considerations.............................. 16 Applications....................................................................................... 1 Basic Voltage Reference Connections ..................................... 16 Pin Configuration............................................................................. 1 Noise Performance ..................................................................... 16 General Description ......................................................................... 1 Turn-On Time ............................................................................ 16 ADR42x Products............................................................................. 1 Applications..................................................................................... 17 Revision History ............................................................................... 2 Output Adjustment .................................................................... 17 Specifications..................................................................................... 3 ADR420 Electrical Specifications............................................... 3 Reference for Converters in Optical Network Control Circuits......................................................................................... 17 ADR421 Electrical Specifications............................................... 4 High Voltage Floating Current Source .................................... 17 ADR423 Electrical Specifications............................................... 5 Kelvin Connections.................................................................... 18 ADR425 Electrical Specifications............................................... 6 Dual-Polarity References........................................................... 18 Absolute Maximum Ratings............................................................ 7 Programmable Current Source ................................................ 19 Thermal Resistance ...................................................................... 7 Programmable DAC Reference Voltage .................................. 19 ESD Caution.................................................................................. 7 Precision Voltage Reference for Data Converters.................. 20 Pin Configurations and Function Descriptions ........................... 8 Precision Boosted Output Regulator ....................................... 20 Typical Performance Characteristics ............................................. 9 Outline Dimensions ....................................................................... 21 Terminology .................................................................................... 15 Ordering Guide .......................................................................... 22 Theory of Operation ...................................................................... 16 REVISION HISTORY 5/11—Rev. H to Rev. I Added Endnote 1 in Table 2............................................................ 4 Added Endnote 1 in Table 3............................................................ 5 Added Endnote 1 in Table 4............................................................ 6 Added Endnote 1 in Table 5............................................................ 7 Deleted A Negative Precision Reference Without Precision Resistors Section ............................................................................. 17 Deleted Figure 42; Renumbered Sequentially ............................ 17 Updated Outline Dimensions ....................................................... 21 Changes to Ordering Guide .......................................................... 22 6/07—Rev. G to Rev. H Changes to Table 2............................................................................ 3 Changes to Table 3............................................................................ 4 Changes to Table 4............................................................................ 5 Changes to Table 5............................................................................ 6 Updated Outline Dimensions ....................................................... 21 Changes to Ordering Guide .......................................................... 22 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 10/01—Rev. 0 to Rev. A Addition of ADR423 and ADR425 to ADR420/ADR421...............................................................Universal 5/01—Revision 0: Initial Version Rev. I | Page 2 of 24 ADR420/ADR421/ADR423/ADR425 SPECIFICATIONS ADR420 ELECTRICAL SPECIFICATIONS VIN = 5.0 V to 15.0 V, TA = 25°C, unless otherwise noted. Table 2. Parameter OUTPUT VOLTAGE A Grade B Grade INITIAL ACCURACY 1 A Grade Symbol VOUT Conditions Typ Max Unit 2.045 2.047 2.048 2.048 2.051 2.049 V V +3 +0.15 +1 +0.05 mV % mV % 2 1 10 3 10 35 ppm°C ppm/°C V ppm/V 70 ppm/mA 500 600 μA μA μV p-p nV/√Hz μs ppm ppm dB mA VOUTERR −3 −0.15 −1 −0.05 B Grade TEMPERATURE COEFFICIENT A Grade B Grade SUPPLY VOLTAGE HEADROOM LINE REGULATION VIN − VOUT ∆VOUT/∆VIN LOAD REGULATION ∆VOUT/∆IL IL = 0 mA to 10 mA, −40°C < TA < +125°C 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 ∆VOUT VOUT_HYS RRR ISC No load −40°C < TA < +125°C 0.1 Hz to 10 Hz 1 kHz 1 Min TCVOUT −40°C < TA < +125°C 2 VIN = 5 V to 18 V, −40°C < TA < +125°C 1000 hours fIN = 1 kHz Initial accuracy does not include shift due to solder heat effect. Rev. I | 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 = 25°C, unless otherwise noted. Table 3. Parameter OUTPUT VOLTAGE A Grade B Grade INITIAL ACCURACY 1 A Grade Symbol VOUT Conditions Typ Max Unit 2.497 2.499 2.500 2.500 2.503 2.501 V V +3 +0.12 +1 +0.04 mV % mV % 2 1 10 3 10 35 ppm/°C ppm/°C V ppm/V 70 ppm/mA 500 600 μA μA μV p-p nV/√Hz μs ppm ppm dB mA VOUTERR −3 −0.12 −1 −0.04 B Grade TEMPERATURE COEFFICIENT A Grade B Grade SUPPLY VOLTAGE HEADROOM LINE REGULATION VIN − VOUT ∆VOUT/∆VIN LOAD REGULATION ∆VOUT/∆IL 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 ∆VOUT VOUT_HYS RRR ISC 1 Min TCVOUT −40°C < TA < +125°C 2 VIN = 5 V to 18 V, −40°C < TA < +125°C IL = 0 mA to 10 mA, −40°C < TA < +125°C No load −40°C < TA < +125°C 0.1 Hz to 10 Hz 1 kHz 1000 hours fIN = 1 kHz Initial accuracy does not include shift due to solder heat effect. Rev. I | 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 = 25°C, unless otherwise noted. Table 4. Parameter OUTPUT VOLTAGE A Grade B Grade INITIAL ACCURACY 1 A Grade Symbol VOUT Conditions Typ Max Unit 2.996 2.9985 3.000 3.000 3.004 3.0015 V V +4 +0.13 +1.5 +0.04 mV % mV % 2 1 10 3 10 35 ppm/°C ppm/°C V ppm/V 70 ppm/mA 500 600 μA μA μV p-p nV/√Hz μs ppm ppm dB mA VOUTERR −4 −0.13 −1.5 −0.04 B Grade TEMPERATURE COEFFICIENT A Grade B Grade SUPPLY VOLTAGE HEADROOM LINE REGULATION VIN − VOUT ∆VOUT/∆VIN LOAD REGULATION ∆VOUT/∆IL 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 ∆VOUT VOUT_HYS RRR ISC 1 Min TCVOUT −40°C < TA < +125°C 2 VIN = 5 V to 18 V, −40°C < TA < +125°C IL = 0 mA to 10 mA, −40°C < TA < +125°C No load −40°C < TA < +125°C 0.1 Hz to 10 Hz 1 kHz 1000 hours fIN = 1 kHz Initial accuracy does not include shift due to solder heat effect. Rev. I | 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 = 25°C, unless otherwise noted. Table 5. Parameter OUTPUT VOLTAGE A Grade B Grade INITIAL ACCURACY 1 A Grade Symbol VOUT Conditions Typ Max Unit 4.994 4.998 5.000 5.000 5.006 5.002 V V +6 +0.12 +2 +0.04 mV % mV % 2 1 10 3 10 35 ppm/°C ppm/°C V ppm/V 70 ppm/mA 500 600 μA μA μV p-p nV/√Hz μs ppm ppm dB mA VOUTERR −6 −0.12 −2 −0.04 B Grade TEMPERATURE COEFFICIENT A Grade B Grade SUPPLY VOLTAGE HEADROOM LINE REGULATION VIN − VO ∆VO/∆VIN LOAD REGULATION ∆VO/∆IL 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 1 Min TCVOUT −40°C < TA < +125°C 2 VIN = 7 V to 18 V, −40°C < TA < +125°C IL = 0 mA to 10 mA, −40°C < TA < +125°C No load −40°C < TA < +125°C 0.1 Hz to 10 Hz 1 kHz 1000 hours fIN = 1 kHz Initial accuracy does not include shift due to solder heat effect. Rev. I | Page 6 of 24 390 3.4 110 10 50 40 −75 27 ADR420/ADR421/ADR423/ADR425 ABSOLUTE MAXIMUM RATINGS These ratings apply at 25°C, unless otherwise noted. THERMAL RESISTANCE Table 6. θJA is specified for the worst-case conditions, that is, θJA is specified for devices soldered in the circuit board for surfacemount packages. Parameter Supply Voltage Output Short-Circuit Duration to GND Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature (Soldering, 60 sec) Rating 18 V Indefinite −65°C to +150°C −40°C to +125°C −65°C to +150°C 300°C 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 8-Lead MSOP (RM) 8-Lead SOIC (R) ESD CAUTION Rev. I | Page 7 of 24 θJA 190 130 Unit °C/W °C/W ADR420/ADR421/ADR423/ADR425 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS 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) 02432-002 NIC 3 6 Figure 2. 8-Lead SOIC, 8-Lead MSOP Pin Configuration 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. I | 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 80 110 125 02432-007 VOUT (V) 2.0495 02432-004 VOUT (V) TYPICAL PERFORMANCE CHARACTERISTICS 5.0007 5.0005 –40 –10 TEMPERATURE (°C) 20 50 80 110 125 TEMPERATURE (°C) Figure 3. ADR420 Typical Output Voltage vs. Temperature Figure 6. 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 +25°C 0.40 –40°C 0.35 02432-005 0.30 2.4997 2.4995 –40 +125°C 0.45 –10 20 50 80 110 0.25 125 02432-008 VOUT (V) 2.5009 4 6 8 TEMPERATURE (°C) 10 12 14 15 INPUT VOLTAGE (V) Figure 4. ADR421 Typical Output Voltage vs. Temperature Figure 7. ADR420 Supply Current vs. Input Voltage 0.55 3.0010 3.0008 0.50 SUPPLY CURRENT (mA) 3.0006 3.0002 3.0000 2.9998 2.9996 2.9994 +125°C 0.40 +25°C 0.35 –40°C –10 20 50 80 110 125 TEMPERATURE (°C) 0.25 02432-009 2.9992 2.9990 –40 0.45 0.30 02432-006 VOUT (V) 3.0004 4 6 8 10 12 14 INPUT VOLTAGE (V) Figure 5. ADR423 Typical Output Voltage vs. Temperature Figure 8. ADR421 Supply Current vs. Input Voltage 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 +25°C 0.35 –40°C 0.30 4 6 8 10 12 14 VIN = 5V 40 30 VIN = 6.5V 20 10 02432-010 0.25 50 0 –40 15 02432-013 SUPPLY CURRENT (mA) +125°C 0.45 –10 INPUT VOLTAGE (V) 20 50 80 110 125 TEMPERATURE (°C) Figure 9. ADR423 Supply Current vs. Input Voltage Figure 12. ADR421 Load Regulation vs. Temperature 0.55 70 IL = 0mA TO 10mA 60 LOAD REGULATION (ppm/mA) +125°C 0.45 0.40 +25°C 0.35 –40°C 0.30 6 8 10 12 14 VIN = 7V 40 30 VIN = 15V 20 10 02432-011 0.25 50 0 –40 15 02432-014 SUPPLY CURRENT (mA) 0.50 –10 INPUT VOLTAGE (V) Figure 10. ADR425 Supply Current vs. Input Voltage 35 LOAD REGULATION (ppm/mA) 30 50 40 VIN = 4.5V 20 –10 20 50 110 125 80 110 25 20 15 10 5 0 –40 125 TEMPERATURE (°C) 02432-015 10 02432-012 LOAD REGULATION (ppm/mA) 60 0 –40 80 VIN = 15V IL = 0mA TO 10mA IL = 0mA TO 5mA 30 50 Figure 13. ADR423 Load Regulation vs. Temperature 70 VIN = 6V 20 TEMPERATURE (°C) –10 20 50 80 110 125 TEMPERATURE (°C) Figure 11. ADR420 Load Regulation vs. Temperature Figure 14. ADR425 Load Regulation vs. Temperature Rev. I | 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 80 8 6 4 2 02432-016 0 –40 10 02432-019 LINE REGULATION (ppm/V) 5 0 –40 110 125 –10 TEMPERATURE (°C) 20 50 80 110 125 TEMPERATURE (°C) Figure 15. ADR420 Line Regulation vs. Temperature Figure 18. ADR425 Line Regulation vs. Temperature 6 2.5 VIN = 5V TO 15V 4 3 2 0 –40 02432-017 1 –10 20 50 80 110 2.0 –40°C +85°C 1.0 0.5 0 125 +25°C 1.5 02432-020 DIFFERENTIAL VOLTAGE (V) LINE REGULATION (ppm/V) 5 0 1 TEMPERATURE (°C) 2 3 4 5 LOAD CURRENT (mA) Figure 16. ADR421 Line Regulation vs. Temperature Figure 19. ADR420 Minimum Input/Output Voltage Differential vs. Load Current 9 2.5 VIN = 5V TO 15V 6 5 4 3 2 1 0 –40 –10 20 50 80 2.0 –40°C +125°C 1.0 0.5 0 110 TEMPERATURE (°C) +25°C 1.5 02432-021 DIFFERENTIAL VOLTAGE (V) 7 02432-018 LINE REGULATION (ppm/V) 8 0 1 2 3 4 LOAD CURRENT (mA) Figure 17. ADR423 Line Regulation vs. Temperature Figure 20. ADR421 Minimum Input/Output Voltage Differential vs. Load Current Rev. I | Page 11 of 24 5 ADR420/ADR421/ADR423/ADR425 2.0 –40°C 1.5 1µV/DIV +25°C +125°C 1.0 0 02432-025 0.5 02432-022 DIFFERENTIAL VOLTAGE (V) 2.5 0 1 2 3 4 TIME (1s/DIV) 5 LOAD CURRENT (mA) Figure 24. ADR421 Typical Noise Voltage 0.1 Hz to 10 Hz Figure 21. ADR423 Minimum Input/Output Voltage Differential vs. Load Current 2.0 –40°C 1.5 50µV/DIV +25°C +125°C 1.0 0 02432-026 0.5 02432-023 DIFFERENTIAL VOLTAGE (V) 2.5 0 1 2 3 4 TIME (1s/DIV) 5 LOAD CURRENT (mA) Figure 22. ADR425 Minimum Input/Output Voltage Differential vs. Load Current 1k 15 10 ADR423 100 ADR420 10 10 40 50 60 70 80 90 100 110 120 130 MORE –40 –30 –20 –10 0 10 20 30 0 02432-024 5 ADR425 ADR421 02432-027 SAMPLE SIZE – 160 20 –100 –90 –80 –70 –60 –50 NUMBER OF PARTS 25 TEMPERATURE +25°C –40°C +125°C +25°C VOLTAGE NOISE DENSITY (nV/ Hz) 30 Figure 25. Typical Noise Voltage 10 Hz to 10 kHz 100 1k FREQUENCY (Hz) DEVIATION (ppm) Figure 26. Voltage Noise Density vs. Frequency Figure 23. ADR421 Typical Hysteresis Rev. I | Page 12 of 24 10k ADR420/ADR421/ADR423/ADR425 CBYPASS = 0µF CL = 100nF LINE INTERRUPTION 1mA LOAD VOUT VIN 1V/DIV 500mV/DIV LOAD OFF VOUT 500mV/DIV 2V/DIV 02432-028 02432-031 LOAD ON TIME (100µs/DIV) TIME (100µs/DIV) Figure 27. ADR421 Line Transient Response, no CBYPASS CBYPASS = 0.1µF Figure 30. ADR421 Load Transient Response, CL = 100 nF CIN = 0.01µF NO LOAD LINE INTERRUPTION VOUT VIN 2V/DIV 500mV/DIV VIN VOUT 500mV/DIV 02432-029 02432-032 2V/DIV TIME (4µs/DIV) TIME (100µs/DIV) Figure 28. ADR421 Line Transient Response, CBYPASS = 0.1 μF CL = 0µF Figure 31. ADR421 Turn-Off Response CIN = 0.01µF NO LOAD 1mA LOAD 2V/DIV VOUT 1V/DIV VOUT LOAD OFF 2V/DIV 2V/DIV LOAD ON 02432-030 02432-033 VIN TIME (4µs/DIV) TIME (100µs/DIV) Figure 32. ADR421 Turn-On Response Figure 29. ADR421 Load Transient Response, no CL Rev. I | Page 13 of 24 ADR420/ADR421/ADR423/ADR425 50 CL = 0.01µF NO INPUT CAP 45 VOUT 40 OUTPUT IMPEDANCE (Ω) 2V/DIV VIN 2V/DIV 35 30 ADR425 25 ADR423 20 ADR421 15 5 0 10 TIME (4µs/DIV) ADR420 100 1k 10k 02432-037 02432-034 10 100k FREQUENCY (Hz) Figure 33. ADR421 Turn-Off Response Figure 36. Output Impedance vs. Frequency 0 CL = 0.01µF NO INPUT CAP –10 2V/DIV RIPPLE REJECTION (dB) –20 VOUT 2V/DIV –30 –40 –50 –60 –70 02432-035 02432-038 –80 VIN –90 –100 10 TIME (4µs/DIV) 100 1k 10k 100k FREQUENCY (Hz) Figure 37. Ripple Rejection vs. Frequency Figure 34. ADR421 Turn-On Response CBYPASS = 0.1µF RL = 500Ω CL = 0 5V/DIV VIN 2V/DIV 02432-036 VOUT TIME (100µs/DIV) Figure 35. ADR421 Turn-On/Turn-Off Response Rev. I | Page 14 of 24 1M ADR420/ADR421/ADR423/ADR425 TERMINOLOGY Temperature Coefficient The change of output voltage over the operating temperature range is normalized by the output voltage at 25°C, and expressed in ppm/°C as TCVOUT ( ppm / °C ) = VOUT (T2 ) − VOUT (T1 ) VOUT ( 25°C ) × (T2 − T1 ) × 10 6 VOUT _ HYS = VOUT ( 25°C ) − VOUT _ TC VOUT _ HYS ( ppm) = where: VOUT (25°C) = VOUT at 25°C. VOUT (T1) = VOUT at Temperature 1. VOUT (T2) = VOUT at Temperature 2. 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 per million per milliampere, or ohms of dc output resistance. Long-Term Stability Typical shift of output voltage at 25°C on a sample of parts subjected to operation life test of 1000 hours at 125°C. ΔVOUT = VOUT (t 0 ) − VOUT (t 1 ) ΔVOUT ( ppm) = VOUT (t 0 ) − VOUT (t 1 ) VOUT (t 0 ) Thermal Hysteresis The change of output voltage after the device is cycled through temperatures from +25°C to −40°C to +125°C and back to +25°C. This is a typical value from a sample of parts put through such a cycle. × 10 6 where: VOUT (t0) = VOUT at 25°C at Time 0. VOUT (t1) = VOUT at 25°C after 1000 hours operation at 125°C. VOUT ( 25°C ) − VOUT _ TC VOUT ( 25°C ) × 10 6 where: VOUT (25°C) = VOUT at 25°C. VOUT_TC = VOUT at 25 °C after temperature cycle at +25°C to −40°C to +125°C and back to +25°C. 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 μF to 10 μF capacitor on the input improves transient response in applications where the supply suddenly changes. An additional 0.1 μF 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 μF, 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 μF to 10 μF 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, which depends on the size of the selected capacitor. Rev. I | 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. DEVICE POWER DISSIPATION CONSIDERATIONS 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 × θJA + TA where: TJ and TA are the junction temperature and the ambient temperature, respectively. PD is the device power dissipation. θJA 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 39 illustrates the basic configuration for the ADR42x family of references. Other than a 0.1 μF capacitor at the output to help improve noise suppression, a large output capacitor at the output is not required for circuit stability. Figure 38 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 × (ΔVP − R1 × IPTAT) Each ADR42x device is created by on-chip adjustment of R2 and R3 to achieve the specified reference output. I1 VIN I1 ADR420/ADR421/ ADR423/ADR425 IPTAT VOUT R2 10µF + 2 0.1µF *EXTRA CHANNEL IMPLANT VOUT = G(∆VP – R1 × IPTAT) Figure 38. Simplified Schematic R3 GND 02432-039 R1 NIC 3 4 ADR420/ ADR421/ ADR423/ ADR425 8 TP 7 NIC OUTPUT 6 TOP VIEW (Not to Scale) 5 TRIM 0.1µF NIC = NO INTERNAL CONNECTION TP = TEST PIN (DO NOT CONNECT) Figure 39. Basic Voltage Reference Configuration NOISE PERFORMANCE The noise generated by ADR42x references is typically less than 2 μV p-p over the 0.1 Hz to 10 Hz band for the ADR420, ADR421, and ADR423. Figure 24 shows the 0.1 Hz to 10 Hz noise of the ADR421, which is only 1.75 μV 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 * ∆VP TP 1 VIN (1) where: G is the gain of the reciprocal of the divider ratio. ΔVP is the difference in pinch-off voltage between the two JFETs. IPTAT is the positive temperature coefficient correction current. (2) 02432-040 The ADR42x series of references uses a 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. 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 31 to Figure 35 show the turn-on settling time for the ADR421. Rev. I | Page 16 of 24 ADR420/ADR421/ADR423/ADR425 APPLICATIONS SOURCE FIBER OUTPUT ADJUSTMENT GIMBAL + SENSOR 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. DESTINATION FIBER LASER BEAM MEMS MIRROR ACTIVATOR LEFT AMPL PREAMP ACTIVATOR RIGHT AMPL ADR421 CONTROL ELECTRONICS ADR421 DAC ADC DAC ADR421 2 GND 4 TRIM 5 Figure 41. All Optical Router Network HIGH VOLTAGE FLOATING CURRENT SOURCE R1 470kΩ R2 RP 10kΩ 10kΩ (ADR420) 15kΩ (ADR421) The circuit in Figure 42 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. Figure 40. Output Trim Adjustment +VS SST111 VISHAY REFERENCE FOR CONVERTERS IN OPTICAL NETWORK CONTROL CIRCUITS 2 In the high capacity, all optical router network of Figure 41, 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 wavelength 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. Rev. I | Page 17 of 24 VIN ADR420/ ADR421/ ADR423/ ADR425 VOUT 6 OP09 2N3904 GND 4 RL 2.10kΩ –VS 02432-044 ADR420/ ADR421/ ADR423/ ADR425 DSP OUTPUT VOUT = ±0.5% VOUT 6 02432-041 VIN 02432-042 INPUT Figure 42. High Voltage Floating Current Source ADR420/ADR421/ADR423/ADR425 KELVIN CONNECTIONS DUAL-POLARITY REFERENCES 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 mΩ/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 × IL) at the load. However, the Kelvin connection in Figure 43 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. 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 1µF 0.1µF 2 VIN VOUT 6 U1 ADR425 GND V+ TRIM 5 U2 OP1177 –5V R3 5kΩ 02432-046 V– –10V Figure 44. +5 V and −5 V Reference Using ADR425 +2.5V +10V 2 VIN A1 RLW VOUT SENSE A1 = OP191 VOUT 6 U1 VOUT FORCE RL 4 2 VIN ADR425 GND 4 R1 5.6kΩ TRIM 5 R2 5.6kΩ Figure 43. Advantage of Kelvin Connection –2.5V V+ U2 OP1177 V– –10V 02432-047 RLW 02432-045 VOUT 6 GND R2 10kΩ +10V 4 VIN ADR420/ ADR421/ ADR423/ ADR425 +5V R1 10kΩ Figure 45. +2.5 V and −2.5 V Reference Using ADR425 Rev. I | Page 18 of 24 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 47. The relationship of VREFx to VREF depends on the digital code and the ratio of R1 and R, and is given by ⎛ R2 A + R2 B ⎞ ⎜ ⎟ R1 ⎝ ⎠ IL = × VW R2 B (3) R2 ⎞ ⎛ VREF × ⎜1 + ⎟ R1 ⎠ ⎝ VREF x = D R2 ⎞ ⎛ ⎜1 + N × ⎟ 2 R1 ⎠ ⎝ and D 2N × V REF (4) where: D is the decimal equivalent of the input code. N is the number of bits. where: D is the decimal equivalent of input code. N is the number of bits. VREF is the applied external reference. VREFx is the reference voltage for DACs A to D. C1 10pF VDD R1' 50kΩ 2 TRIM ADR425 4 Table 9. VREFx vs. R1 and R2 VDD R1, R2 R1 = R2 R1 = R2 R1 = R2 R1 = 3R2 R1 = 3R2 R1 = 3R2 5 U1 GND R2' 1kΩ VOUT 6 AD5232 U2 DIGITAL POT VDD C2 10pF V– A U2 B W V+ A2 OP2177 V+ A1 OP2177 V– VSS R2B 10Ω VSS R1 50kΩ R2A 1kΩ VL LOAD IL 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 02432-048 VIN (5) Figure 46. Programmable Current Source 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 46, 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, avoiding 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. VREF A VOUTA R1 ±0.1% VREF DACA VIN VREF B VOUTB DACB VREF C VOUTC DACC VREF D R2 ±0.1% VOUTD DACD ADR425 VOB = VREF x (DB) VOC = VREF x (DC) VOD = VREF x (DD) AD7398 Figure 47. Programmable DAC Reference Rev. I | Page 19 of 24 02432-049 VW = 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 48. 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 (Σ-Δ) ADC, calibration microcontroller with on-chip static RAM, clock oscillator, and serial communications port. +5V ANALOG SUPPLY 0.1µF 10µF VIN DVDD SLEEP VOUT VREF ADR420/ ADR421/ ADR423/ ADR425 CS DATA READY READ (TRANSMIT) SCLK SERIAL CLOCK SDATA SERIAL CLOCK CLKIN BP/UP CAL CALIBRATE ANALOG INPUT ANALOG GROUND AIN AGND 0.1µF AVSS –5V ANALOG SUPPLY 0.1µF CLKOUT SC1 SC2 DGND 0.1µF DVSS 10µF 02432-050 RANGES SELECT 5V 2 U1 VIN VOUT 6 ADR421 RL 25Ω 5 Figure 48. Voltage Reference for 16-Bit ADC AD7701 Rev. I | Page 20 of 24 VOUT 2N7002 + V+ U2 AD8601 – V– Figure 49. Precision Boosted Output Regulator 0.1µF MODE DRDY GND N1 VIN TRIM GND 4 AD7701 AVDD 0.1µF A precision voltage output with boosted current capability can be realized with the circuit shown in Figure 49. In this circuit, U2 forces VOUT 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. 02432-051 PRECISION VOLTAGE REFERENCE FOR DATA CONVERTERS ADR420/ADR421/ADR423/ADR425 OUTLINE DIMENSIONS 5.00 (0.1968) 4.80 (0.1890) 8 4.00 (0.1574) 3.80 (0.1497) 5 1 6.20 (0.2441) 5.80 (0.2284) 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.31 (0.0122) COPLANARITY 0.10 SEATING PLANE 0.50 (0.0196) 0.25 (0.0099) 45° 8° 0° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 012407-A 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 50. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) 3.20 3.00 2.80 3.20 3.00 2.80 8 1 5.15 4.90 4.65 5 4 PIN 1 IDENTIFIER 0.65 BSC 0.95 0.85 0.75 15° MAX 1.10 MAX 0.40 0.25 6° 0° 0.23 0.09 COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 51. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters Rev. I | Page 21 of 24 0.80 0.55 0.40 10-07-2009-B 0.15 0.05 COPLANARITY 0.10 ADR420/ADR421/ADR423/ADR425 ORDERING GUIDE Model 1 ADR420ARZ ADR420ARZ-REEL7 ADR420ARMZ ADR420ARMZ-REEL7 ADR420BRZ ADR420BRZ-REEL7 ADR421AR ADR421ARZ ADR421ARZ-REEL7 ADR421ARMZ ADR421ARMZ-REEL7 ADR421BR ADR421BR-REEL7 ADR421BRZ ADR421BRZ-REEL7 ADR423ARZ ADR423ARZ-REEL7 ADR423ARMZ ADR423ARMZ-REEL7 ADR423BRZ ADR423BRZ-REEL7 ADR425ARZ ADR425ARZ-REEL7 ADR425ARMZ ADR425ARMZ-REEL7 ADR425BR ADR425BR-REEL7 ADR425BRZ ADR425BRZ-REEL7 1 Output Voltage, VOUT (V) 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 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 Initial Accuracy mV % 3 0.15 3 0.15 3 0.15 3 0.15 1 0.05 1 0.05 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 1.5 0.04 1.5 0.04 6 0.12 6 0.12 6 0.12 6 0.12 2 0.04 2 0.04 2 0.04 2 0.04 Temperature Coefficient (ppm/°C) 10 10 10 10 3 3 10 10 10 10 10 3 3 3 3 10 10 10 10 3 3 10 10 10 10 3 3 3 3 Temperature Range −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C Z = RoHS Compliant Part. # denotes RoHS-compliant product may be top or bottom marked. Rev. I | Page 22 of 24 Package Description 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N Package Option R-8 R-8 RM-8 RM-8 R-8 R-8 R-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 R-8 R-8 R-8 R-8 RM-8 RM-8 R-8 R-8 R-8 R-8 Branding L0C L0C R06 R06 R0U R0U R7A# R7A# ADR420/ADR421/ADR423/ADR425 NOTES Rev. I | Page 23 of 24 ADR420/ADR421/ADR423/ADR425 NOTES ©2001–2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D02432-0-5/11(I) Rev. I | Page 24 of 24