ADR3450

Micropower, High Accuracy Voltage References ADR3425/ADR3450 FEATURES Initial accuracy: ±0.1% (max) Maximum temperature coefficient: 8 ppm/°C Operating temperature range: −40°C to +125°C Output current: +10 mA source/−3 mA sink Low quiescent current: 100 μA (max) Low dropout voltage: 250 mV at 2 mA Output noise (0.1 Hz to 10 Hz): < 18 μV p-p at 2.5 V typ 6-lead SOT-23 package PIN CONFIGURATION GND FORCE 1 GND SENSE 2 ENABLE 3 ADR3425/ ADR3450 TOP VIEW (Not to Scale) 6 VOUT FORCE VOUT SENSE VIN 08440-001 5 4 Figure 1. 6-Lead SOT-23 APPLICATIONS Precision data acquisition systems High resolution data converters Industrial instrumentation Medical devices Automotive controls Battery-powered devices GENERAL DESCRIPTION The ADR3425/ADR3450 are low-cost, low-power, high precision CMOS voltage references, featuring ±0.1% initial accuracy, low operating current, and low output noise in a small SOT-23 package. For high accuracy, output voltage and temperature coefficient are trimmed digitally during final assembly using Analog Devices, Inc., patented DigiTrim® technology. Stability and system reliability are further improved by the low output voltage hysteresis of the device and low long-term output voltage drift. Furthermore, the low operating current of the device (100 μA maximum) facilitates usage in low-power devices, while its low output noise helps maintain signal integrity in critical signal processing systems. The ADR3425/ADR3450 are available in a wide range of output voltages, all of which are specified over the industrial temperature range of −40°C to +125°C. Table 1. Selection Guide Model ADR3425 ADR3450 Output Voltage (V) 2.500 5.000 Input Voltage Range (V) 2.7 to 5.5 5.2 to 5.5 Table 2. Voltage Reference Choices from Analog Devices VOUT (V) 0.5/1.0 2.048 2.5 Low Cost/ Low Power ADR360 ADR3425 AD1582 ADR361 AD1583 ADR363 ADR366 AD1584 ADR364 ADR3450 AD1585 ADR365 Ultralow Power REF191 ADR291 REF192 REF193 REF196 ADR292 REF198 ADR293 REF195 Low Noise ADR130 ADR430 ADR440 ADR431 ADR441 ADR433 ADR443 ADR434 ADR444 ADR435 ADR445 High Voltage, High Performance ADR03 AD780 ADR06 AD780 3.0 3.3 4.096 5.0 10.0 ADR02 AD780 AD586 ADR01 AD587 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 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 ©2010 Analog Devices, Inc. All rights reserved. ADR3425/ADR3450 TABLE OF CONTENTS Features .............................................................................................. 1  Applications ....................................................................................... 1  Pin Configuration .............................................................................. 1  General Description ......................................................................... 1  Revision History ............................................................................... 2  Specifications..................................................................................... 3  ADR3425 Electrical Characteristics .......................................... 3  ADR3450 Electrical Characteristics .......................................... 4  Absolute Maximum Ratings............................................................ 5  Thermal Resistance ...................................................................... 5  ESD Caution .................................................................................. 5  Pin Configuration and Function Descriptions ............................. 6  Typical Performance Characteristics ............................................. 7  Terminology .................................................................................... 13  Theory of Operation ...................................................................... 14  Power Dissipation....................................................................... 14  Applications..................................................................................... 15  Basic Voltage Reference Connection ....................................... 15  Input and Output Capacitors .................................................... 15  4-Wire Kelvin Connections ...................................................... 15  VIN Slew Rate Considerations ................................................... 15  Shutdown/Enable Feature ......................................................... 15  Sample Applications ................................................................... 16  Outline Dimensions ....................................................................... 17  Ordering Guide .......................................................................... 17  REVISION HISTORY 3/10—Revision 0: Initial Version Rev. 0 | Page 2 of 20 ADR3425/ADR3450 SPECIFICATIONS ADR3425 ELECTRICAL CHARACTERISTICS VIN = 2.7 V to 5.5 V, IL = 0 mA, TA = 25°C, unless otherwise noted. Table 3. Parameter OUTPUT VOLTAGE INITIAL ACCURACY TEMPERATURE COEFFICIENT LINE REGULATION LOAD REGULATION Sourcing Sinking OUTPUT CURRENT CAPACITY Sourcing Sinking QUIESCENT CURRENT Normal Operation Shutdown DROPOUT VOLTAGE1 ENABLE PIN Shutdown Voltage Enable Voltage ENABLE Pin Leakage Current OUTPUT VOLTAGE NOISE OUTPUT VOLTAGE NOISE DENSITY OUTPUT VOLTAGE HYSTERESIS2 RIPPLE REJECTION RATIO LONG-TERM STABILITY TURN-ON SETTLING TIME 1 2 Symbol VOUT VOERR TCVOUT ΔVO/ΔVIN ΔVO/ΔIL Conditions Min 2.4975 Typ 2.500 −40°C ≤ TA ≤ +125°C VIN = 2.7 V to 5.5 V VIN = 2.7 V to 5.5 V, −40°C ≤ TA ≤ +125°C IL = 0 mA to +10 mA, −40°C ≤ TA ≤ +125°C, VIN = 3.0 V to 5.0 V IL = 0 mA to −3 mA, −40°C ≤ TA ≤ +125°C, VIN = 3.0 V to 5.0 V 2.5 Max 2.5025 ±0.1 ±2.5 8 50 120 30 50 Unit V % mV ppm/°C ppm/V ppm/V ppm/mA ppm/mA IL VIN = 3.0 V to 5.5 V VIN = 3.0 V to 5.5 V IQ ENABLE ≥ VIN × 0.85 ENABLE = VIN, −40°C ≤ TA ≤ +125°C ENABLE ≤ 0.7 V IL = 0 mA, TA = −40°C ≤ TA ≤ +125°C IL = 2 mA, TA = −40°C ≤ TA ≤ +125°C 0 VIN × 0.85 ENABLE = VIN, TA = −40°C ≤ TA ≤ +125°C f = 0.1 Hz to 10 Hz f = 10 Hz to 10 kHz f = 1 kHz TA = +25°C to −40°C to +125°C to +25°C fIN = 60 Hz 1000 hours at 50°C 1 18 42 1.2 70 −60 30 800 85 100 5 200 250 0.7 VIN 3 μA μA μA mV mV V V μA μV p-p μV rms μV/√Hz ppm dB ppm μs 10 −3 mA mA VDO VL VH IEN en p-p en ΔVOUT_HYS RRR ΔVOUT_LTD tR Refer to the minimum difference between VIN and VOUT such that VOUT maintains a minimum accuracy of 0.1%. See the Terminology section. See the Terminology section. The part is placed through the temperature cycle in the order of temperatures shown. Rev. 0 | Page 3 of 20 ADR3425/ADR3450 ADR3450 ELECTRICAL CHARACTERISTICS VIN = 5.2 V to 5.5 V, IL = 0 mA, TA = 25°C, unless otherwise noted. Table 4. Parameter OUTPUT VOLTAGE INITIAL ACCURACY TEMPERATURE COEFFICIENT LINE REGULATION LOAD REGULATION Sourcing Sinking OUTPUT CURRENT CAPACITY Sourcing Sinking QUIESCENT CURRENT Normal Operation Shutdown DROPOUT VOLTAGE1 ENABLE PIN Shutdown Voltage Enable Voltage ENABLE Pin Leakage Current OUTPUT VOLTAGE NOISE OUTPUT VOLTAGE NOISE DENSITY OUTPUT VOLTAGE HYSTERESIS2 RIPPLE REJECTION RATIO LONG-TERM STABILITY TURN-ON SETTLING TIME 1 2 Symbol VOUT VOERR TCVOUT ΔVO/ΔVIN ΔVO/ΔIL Conditions Min 4.995 Typ 5.000 −40°C ≤ TA ≤ +125°C VIN = 5.2 V to 5.5 V VIN = 5.2 V to 5.5 V, −40°C ≤ TA ≤ +125°C IL = 0 mA to +10 mA, −40°C ≤ TA ≤ +125°C, VIN = 5.5 V IL = 0 mA to −3 mA, −40°C ≤ TA ≤ +125°C, VIN = 5.5 V 2.5 Max 5.005 ±0.1 ±5.0 8 50 120 30 50 Unit V % mV ppm/°C ppm/V ppm/V ppm/mA ppm/mA IL VIN = 5.5 V VIN = 5.5 V IQ ENABLE ≥ VIN × 0.85 ENABLE = VIN, −40°C ≤ TA ≤ +125°C ENABLE ≤ 0.7 V IL = 0 mA, TA = −40°C ≤ TA ≤ +125°C IL = 2 mA, TA = −40°C ≤ TA ≤ +125°C 0 VIN × 0.85 ENABLE = VIN, TA = −40°C ≤ TA ≤ +125°C f = 0.1 Hz to 10 Hz f = 10 Hz to 10 kHz f = 1 kHz TA = +25°C to −40°C to +125°C to +25°C fIN = 60 Hz 1000 hours at 50°C 1 35 60 1.9 70 −58 30 1.2 85 100 5 200 250 0.7 VIN 3 μA μA μA mV mV V V μA μV p-p μV rms μV/√Hz ppm dB ppm ms 10 −3 mA mA VDO VL VH IEN en p-p en ΔVOUT_HYS RRR ΔVOUT_LTD tR Refer to the minimum difference between VIN and VOUT such that VOUT maintains a minimum accuracy of 0.1%. See the Terminology section. See the Terminology section. The part is placed through the temperature cycle in the order of temperatures shown. Rev. 0 | Page 4 of 20 ADR3425/ADR3450 ABSOLUTE MAXIMUM RATINGS TA = 25°C, unless otherwise noted. Table 5. Parameter Supply Voltage ENABLE to GND SENSE Voltage VIN Minimum Slew Rate Operating Temperature Range Storage Temperature Range Junction Temperature Range Rating 6V VIN 0.1 V/ms −40°C to +125°C −65°C to +125°C −65°C to +150°C THERMAL RESISTANCE θJA is specified for the worst-case conditions; that is, a device soldered in a circuit board for surface-mount packages. Table 6. Thermal Resistance Package Type 6-Lead SOT-23 (RJ-6) θJA 230 θJC 92 Unit °C/W ESD CAUTION 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. Rev. 0 | Page 5 of 20 ADR3425/ADR3450 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS GND FORCE 1 GND SENSE 2 ENABLE 3 ADR3425/ ADR3450 TOP VIEW (Not to Scale) 6 VOUT FORCE VOUT SENSE VIN 08440-002 5 4 Figure 2. Pin Configuration Table 7. Pin Function Descriptions Pin No. 1 2 3 4 5 6 1 Mnemonic GND FORCE GND SENSE ENABLE VIN VOUT SENSE VOUT FORCE Description Ground Force Connection 1 . Ground Voltage Sense Connection. Connect directly to point of lowest potential in application1. Enable Connection. Enables or disables the device. Input Voltage Connection. Reference Voltage Output Sensing Connection. Connect directly to the voltage input of load devices1. Reference Voltage Output1. See the Applications section for more information on force/sense connections. Rev. 0 | Page 6 of 20 ADR3425/ADR3450 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. 2.5010 2.5008 2.5006 OUTPUT VOLTAGE (V) 14 VIN = 5.5V 12 LOAD REGULATION (ppm/mA) VIN = 5.5V ΔIL = 0mA TO 10mA CL = 0.1µF 2.5004 2.5002 2.5000 2.4998 2.4996 2.4994 2.4992 –25 –10 5 20 35 50 65 80 95 110 125 08440-003 10 8 6 4 2 0 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (ºC) TEMPERATURE (°C) Figure 3. ADR3425 Output Voltage vs. Temperature 40 35 30 LOAD REGULATION (ppm/mA) Figure 6. ADR3425 Load Regulation vs. Temperature (Sourcing) 20 18 16 14 12 10 8 6 4 2 08440-005 VIN = 5.5V ΔIL = 0mA TO –3mA CL = 0.1µF NUMBER OF DEVICES 25 20 15 10 5 0 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) Figure 4. ADR3425 Temperature Coefficient Distribution 150 130 LINE REGULATION (ppm/V) Figure 7. ADR3425 Load Regulation vs. Temperature (Sinking) 400 ΔVIN = 2.7V TO 5.5V IL = 0 350 –40°C +25°C +125°C 90 70 50 30 10 –10 –30 –40 –25 DROPOUT VOLTAGE (mV) 110 300 250 200 150 100 50 0 –3 –10 5 20 35 50 65 80 95 110 125 08440-009 –2 –1 0 1 2 3 4 5 6 7 8 9 10 TEMPERATURE (°C) LOAD CURRENT (mA) Figure 5. ADR3425 Line Regulation vs. Temperature Figure 8. ADR3425 Dropout Voltage vs. Load Current Rev. 0 | Page 7 of 20 08440-015 08440-013 0 1 2 3 4 5 6 7 8 9 TEMPERATURE COEFFICIENT (ppm/°C) 10 MORE 0 –40 08440-011 2.4990 –40 ADR3425/ADR3450 5.0025 5.0020 5.0015 VIN = 5.5V 5 6 VIN = 5.5V ΔIL = 0mA TO 10mA CL = 0.1µF OUTPUT VOLTAGE (V) 5.0010 5.0005 5.0000 4.9995 4.9990 4.9985 4.9980 08440-004 LOAD REGULATION (ppm/mA) 4 3 2 1 –25 –10 5 20 35 50 65 80 95 110 125 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (ºC) TEMPERATURE (°C) Figure 9. ADR3450 Output Voltage vs. Temperature 45 40 35 NUMBER OF DEVICES 30 25 20 15 10 5 0 LOAD REGULATION (ppm/mA) Figure 12. ADR3450 Load Regulation vs. Temperature (Sourcing) 24 22 20 18 16 14 12 10 8 –40 VIN = 5.5V ΔIL = 0mA TO –3mA CL = 0.1µF 0 1 2 3 4 5 6 7 8 9 10 MORE 08440-006 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE COEFFICIENT (ppm/°C) TEMPERATURE (°C) Figure 10. ADR3450 Temperature Coefficient Distribution 10 8 LINE REGULATION (ppm/V) 6 DROPOUT VOLTAGE (mV) Figure 13. ADR3450 Load Regulation vs. Temperature (Sinking) 350 –40°C +25°C +125°C ΔVIN = 5.2V TO 5.5V IL = 0 300 250 200 150 100 50 0 –3 4 2 0 –2 –4 –6 –8 –25 –10 5 20 35 50 65 80 95 110 125 08440-010 –2 –1 0 1 2 3 4 5 6 7 8 9 10 TEMPERATURE (°C) LOAD CURRENT (mA) Figure 11. ADR3450 Line Regulation vs. Temperature Figure 14. ADR3450 Dropout Voltage vs. Load Current Rev. 0 | Page 8 of 20 08440-016 –10 –40 08440-014 08440-012 4.9975 –40 0 –40 ADR3425/ADR3450 0 RIPPLE REJECTION RATIO (dB VOUT/VIN) –10 –20 –30 –40 –50 –60 –70 –80 –90 10 CL = 1.1µF CIN = 0.1µF 1 10µV/DIV TIME = 1s/DIV CH1 pk-pk = 18µV CH1 RMS = 3.14µV 08440-028 100 1k FREQUENCY (Hz) 10k 100k Figure 15. ADR3425 Output Voltage Noise (0.1 Hz to 10 Hz) Figure 18. ADR3425 Ripple Rejection Ratio vs. Frequency CIN = CL = 0.1µF RL = ∞ 1 VIN = 2V/DIV 1 100µV/DIV TIME = 200µs/DIV 08440-029 TIME = 1s/DIV CH1 pk-pk = 300µV CH1 RMS = 42.0µV VOUT = 1V/DIV Figure 16. ADR3425 Output Voltage Noise (10 Hz to 10 kHz) 12 Figure 19. ADR3425 Start-Up Response 10 NOISE DENSITY (µVp-p /√Hz) ENABLE 8 VENABLE = 1V/DIV VIN = 3.0v CIN = CL = 0.1µF RL = ∞ 6 1 4 VOUT = 1V/DIV TIME = 200µs/DIV 08440-031 2 2 1 10 100 1k 10k FREQUENCY (Hz) 08440-023 0 0.1 Figure 17. ADR3425 Output Noise Spectral Density Figure 20. ADR3425 Restart Response from Shutdown Rev. 0 | Page 9 of 20 08440-030 2 08440-025 ADR3425/ADR3450 0 RIPPLE REJECTION RATIO (dB VOUT/VIN) –10 –20 –30 –40 –50 –60 –70 –80 –90 10 CL = 1.1µF CIN = 0.1µF 1 10µV/DIV 100 1k FREQUENCY (Hz) 10k 100k Figure 21. ADR3450 Output Voltage Noise (0.1 Hz to 10 Hz) Figure 24. ADR3450 Ripple Rejection Ratio vs. Frequency VIN 2V/DIV 1 1 CIN = 0µF CL = 0.1µF RL = ∞ 100µV/DIV 08440-033 VOUT 2V/DIV 2 TIME = 200µs/DIV 08440-034 CH1 pk-pk = 446µV CH1 RMS = 60.3µV Figure 22. ADR3450 Output Voltage Noise (10 Hz to 10 kHz) 12 Figure 25. ADR3450 Start-Up Response 10 NOISE DENSITY (µVp-p/√Hz) ENABLE VENABLE = 2V/DIV VIN = 5.5V CIN = CL = 0.1µF RL = ∞ 8 1 6 VOUT = 2V/DIV 4 TIME = 200µs/DIV 08440-035 2 2 1 10 100 1k 10k FREQUENCY (Hz) 08440-024 0 0.1 Figure 23. ADR3450 Output Noise Spectral Density Figure 26. ADR3450 Restart Response from Shutdown Rev. 0 | Page 10 of 20 08440-026 CH1 pk-pk = 33.4µV CH1 RMS = 5.68µV 08440-032 ADR3425/ADR3450 ENABLE 1V/DIV CIN = CL = 0.1µF VIN = 3V RL = 1kΩ 1 ENABLE 2V/DIV CIN = CL = 0.1µF VIN = 5V RL = 1kΩ 1 08440-036 TIME = 200µs/DIV TIME = 200µs/DIV Figure 27. ADR3425 Shutdown Response Figure 30. ADR3450 Shutdown Response VIN = 100mV/DIV 3.2V 2.7V 500mV/DIV CIN = CL = 0.1µF 1 5.5V CIN = CL = 0.1µF 5.2V 2 VOUT = 10mV/DIV 2 VOUT = 5mV/DIV 08440-037 08440-039 2 VOUT = 1V/DIV 2 VOUT = 2V/DIV TIME = 1ms/DIV 1 TIME = 1ms/DIV Figure 28. ADR3425 Line Transient Response IL +10mA SINKING –3mA CIN = 0.1µF CL = 0.1µF RL = 250Ω SINKING Figure 31. ADR3450 Line Transient Response +10mA SINKING –3mA SOURCING IL SINKING SOURCING CIN = 0.1µF CL = 0.1µF RL = 500Ω 5.0V 2.5V VOUT = 20mV/DIV 08440-038 VOUT = 20mV/DIV TIME = 1ms/DIV TIME = 1ms/DIV 08440-041 Figure 29. ADR3425 Load Transient Response Figure 32. ADR3450 Load Transient Response Rev. 0 | Page 11 of 20 08440-040 ADR3425/ADR3450 100 90 80 VIN = 5.5 V 7 6 5 4 3 2 1 0 –0.050 –0.045 –0.040 –0.035 –0.030 –0.025 –0.020 –0.015 –0.010 –0.005 0 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.050 MORE SUPPLY CURRENT (µA) 70 60 50 40 30 20 10 0 –40 –25 –10 5 20 35 50 65 80 95 110 08440-042 NUMBER OF DEVICES 125 TEMPERATURE (°C) RELATIVE SHIFT IN VOUT (%) Figure 33. Supply Current vs. Temperature 2.0 1.8 1.6 –40°C +25°C +125°C Figure 36. Output Voltage Drift Distribution After Reflow (SHR Drift) 8 TA = +25°C → +150°C → –50°C → +25°C 7 6 SUPPLY CURRENT (mA) NUMBER OF DEVICES 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 5 4 3 2 08440-044 1 0 –120 –110 –20 –10 0 10 –100 –90 –80 –70 –60 –50 –150 –140 ENABLE VOLTAGE (% of VIN) –130 OUTPUT VOLTAGE HYSTERESIS (ppm) Figure 34. Supply Current vs. Enable Pin Voltage 10 CL = 0.1µF CL = 1.1µF Figure 37. Thermally Induced Output Voltage Hysteresis Distribution 80 60 OUTPUT VOLTAGE DRIFT (ppm) OUTPUT IMPEDANCE (Ω) 40 20 0 –20 –40 08440-045 1 0.1 –60 0.1 1 10 100 1k 10k 08440-027 0.01 0.01 –80 0 200 400 –40 –30 600 800 FREQUENCY (Hz) ELAPSED TIME (Hours) Figure 35. ADR3450 Output Impedance vs. Frequency Figure 38. ADR3450 Typical Long-Term Drift (Four Devices, 1000 Hours) Rev. 0 | Page 12 of 20 20 30 40 1000 0 10 20 30 40 50 60 70 80 90 100 08440-008 08440-043 ADR3425/ADR3450 TERMINOLOGY Dropout Voltage (VDO) Dropout voltage, sometimes referred to as supply voltage headroom or supply-output voltage differential, is defined as the minimum voltage differential between the input and output such that the output voltage is maintained to within 0.1% accuracy. VDO = (VIN − VOUT)min | IL = constant Because the dropout voltage depends upon the current passing through the device, it is always specified for a given load current. In series-mode devices, dropout voltage typically increases proportionally to load current; see Figure 8 and Figure 14. Temperature Coefficient (TCVOUT) The temperature coefficient relates the change in output voltage to the change in ambient temperature of the device, as normalized by the output voltage at 25°C. This parameter is expressed in ppm/°C and can be determined by the following equation: TCVOUT = max{VOUT (T1 , T2 , T3 )} − min{VOUT (T1 , T2 , T3 )} VOUT (T2 ) × (T3 − T1 ) × 106 [ ppm / °C] Long-Term Stability (ΔVOUT_LTD) Long-term stability refers to the shift in output voltage at 50°C after 1000 hours of operation in a 50°C environment. Ambient temperature is kept at 50°C to ensure that the temperature chamber does not switch randomly between heating and cooling, which can cause instability over the 1000 hour measurement. This is also expressed as either a shift in voltage or a difference in ppm from the nominal output. ΔVOUT _ LTD = VOUT (t 1 ) − VOUT (t 0 ) [V] ΔVOUT _ LTD = VOUT (t 1 ) − VOUT (t 0 ) VOUT (t 0 ) × 10 6 [ppm] where: VOUT(t0) is the VOUT at 50°C at time 0. VOUT(t1) is the VOUT at 50°C after 1000 hours of operation at 50°C. Line Regulation Line regulation refers to the change in output voltage in response to a given change in input voltage and is expressed in either percent per volt, ppm per volt, or μV per volt change in input voltage. This parameter accounts for the effects of self-heating. Load Regulation Load regulation refers to the change in output voltage in response to a given change in load current and is expressed in μV per mA, ppm per mA, or ohms of dc output resistance. This parameter accounts for the effects of self-heating. Solder Heat Resistance (SHR) Drift SHR drift refers to the permanent shift in output voltage induced by exposure to reflow soldering, expressed in units of ppm. This is caused by changes in the stress exhibited upon the die by the package materials when exposed to high temperatures. This effect is more pronounced in lead-free soldering processes due to higher reflow temperatures. where: VOUT(T) is the output voltage at temperature T and T1 = −40°C. T2 = +25°C. T3 = +125°C. This three-point method ensures that TCVOUT accurately portrays the maximum difference between any of the three temperatures at which the output voltage of the part is measured. The TCVOUT for the ADR3425/ADR3450 is guaranteed via statistical means. This is accomplished by recording output voltage data for a large number of units over temperature, computing TCVOUT for each individual device via the above equation, then defining the maximum TCVOUT limits as the mean TCVOUT for all devices extended by 6 standard deviations (6σ). Thermally Induced Output Voltage Hysteresis (ΔVOUT_HYS) Thermally induced output voltage hysteresis represents the change in output voltage after the device is exposed to a specified temperature cycle. This is expressed as either a shift in voltage or a difference in ppm from the nominal output: ΔVOUT _ HYS = VOUT (25°C ) − VOUT _ TC [V] ΔVOUT _ HYS = VOUT (25°C ) − VOUT _ TC VOUT (25°C ) × 10 6 [ppm] where: VOUT(25°C) is the output voltage at 25°C. VOUT_TC is the output voltage after temperature cycling. Rev. 0 | Page 13 of 20 ADR3425/ADR3450 THEORY OF OPERATION VDD LONG-TERM STABILITY One of the key parameters of the ADR3425/ADR3450 references is long-term stability. Regardless of output voltage, internal testing during development showed a typical drift of approximately 30 ppm after 1,000 hours of continuous, non loaded operation in a +50°C environment. It is important to understand that long-term stability is not guaranteed by design and that the output from the device may shift beyond the typical 30 ppm specification at any time, especially during the first 200 hours of operation. For systems that require highly stable output voltages over long periods of time, the designer should consider burning-in the devices prior to use to minimize the amount of output drift exhibited by the reference over time. See the AN-713 Application Note for more information regarding the effects of long-term drift and how it can be minimized. ENABLE BANDGAP VOLTAGE REFERENCE VBG REF FORCE REF SENSE RFB1 GND FORCE RFB2 08440-046 GND SENSE Figure 39. Block Diagram The ADR3425/ADR3450 use a patented voltage reference architecture to achieve high accuracy, low temperature coefficient (TC), and low noise in a CMOS process. Like all bandgap references, the ADR3425/ADR3450 combine two voltages of opposite TCs to create an output voltage that is nearly independent of ambient temperature. However, unlike traditional bandgap voltage references, the temperatureindependent voltage of the ADR3425/ADR3450 are arranged to be the base-emitter voltage, VBE, of a bipolar transistor at room temperature rather than the VBE extrapolated to 0 K (the VBE of bipolar transistor at 0 K is approximately VG0, the band gap voltage of silicon). A corresponding positive-TC voltage is then added to the VBE voltage to compensate for its negative TC. The key benefit of this technique is that the trimming of the initial accuracy and TC can be performed without interfering with one another, thereby increasing overall accuracy across temperature. Curvature correction techniques further reduce the temperature variation. The bandgap voltage is then buffered and amplified to produce stable output voltages of 2.5 V and 5.0 V. The output buffer can source up to 10 mA and sink up to 3 mA of load current. The ADR3425/ADR3450 leverage Analog Devices patented DigiTrim technology to achieve high initial accuracy and low TC, while precision layout techniques lead to very low long-term drift and thermal hysteresis. POWER DISSIPATION The ADR3425/ADR3450 voltage references are capable of sourcing up to 10 mA of load current at room temperature across the rated input voltage range. However, when used in applications subject to high ambient temperatures, the input voltage and load current should be carefully monitored to ensure that the device does not exceeded its maximum power dissipation rating. The maximum power dissipation of the device can be calculated via the following equation: PD = TJ − TA θ JA [W ] where: PD is the device power dissipation. TJ is the device junction temperature. TA is the ambient temperature. θJA is the package (junction-to-air) thermal resistance. Because of this relationship, acceptable load current in high temperature conditions may be less than the maximum currentsourcing capability of the device. In no case should the part be operated outside of its maximum power rating because doing so can result in premature failure or permanent damage to the device. Rev. 0 | Page 14 of 20 ADR3425/ADR3450 APPLICATIONS BASIC VOLTAGE REFERENCE CONNECTION VIN 2.7V TO 5.5V 1µF 0.1µF 4 3 VIN ENABLE VOUT FORCE 6 VOUT SENSE 5 VREF OUT 2.5V ADR3425 GND SENSE 2 GND FORCE 1 0.1µF 08440-047 back into the internal amplifier and used to automatically correct for the voltage drop across the current-carrying output and ground lines, resulting in a highly accurate output voltage across the load. To achieve the best performance, the sense connections should be connected directly to the point in the load where the output voltage should be the most accurate. See Figure 41 for an example application. OUTPUT CAPACITOR(S) SHOULD BE MOUNTED AS CLOSE TO VOUT PIN AS POSSIBLE. 0.1µF VIN 4V IN Figure 40. Basic Reference Connection The circuit shown in Figure 40 illustrates the basic configuration for the ADR3425/ADR3450. Bypass capacitors should be connected according to the guidelines below. VOUT FORCE 6 SENSE CONNECTIONS SHOULD CONNECT AS CLOSE TO LOAD DEVICE AS POSSIBLE. 08440-048 INPUT AND OUTPUT CAPACITORS A 1 μF to 10 μF electrolytic or ceramic capacitor can be connected to the input to improve transient response in applications where the supply voltage may fluctuate. An additional 0.1 μF ceramic capacitor should be connected in parallel to reduce high frequency supply noise. A ceramic capacitor of at least a 0.1 μF must be connected to the output to improve stability and help filter out high frequency noise. An additional 1 μF to 10 μF electrolytic or ceramic capacitor can be added in parallel to improve transient performance in response to sudden changes in load current; however, the designer should keep in mind that doing so increases the turn-on time of the device. Best performance and stability is attained with low-ESR (for example, less than 1 Ω), low-inductance ceramic chip-type output capacitors (X5R, X7R or similar). If using an electrolytic capacitor on the output, a 0.1 μF ceramic capacitor should be placed in parallel to reduce overall ESR on the output. 1µF 0.1µF 3 ENABLE V 5 OUT SENSE ADR3425 GND SENSE 2 GND FORCE 1 LOAD Figure 41. Application Showing Kelvin Connection It is always advantageous to use Kelvin connections whenever possible. However, in applications where the IR drop is negligible or an extra set of traces cannot be routed to the load, the force and sense pins for both VOUT and GND can simply be tied together and the device can be used in the same fashion as a normal 3-terminal reference (as shown in Figure 40). VIN SLEW RATE CONSIDERATIONS In applications with slow-rising input voltage signals, the reference exhibits overshoot or other transient anomalies that appear on the output. These phenomena also appear during shutdown as the internal circuitry loses power. To avoid such conditions, ensure that the input voltage waveform has both a rising and falling slew rate of at least 0.1 V/ms. 4-WIRE KELVIN CONNECTIONS Current flowing through a PCB trace produces an IR voltage drop, and with longer traces, this drop can reach several millivolts or more, introducing a considerable error into the output voltage of the reference. A 1 inch long, 5 millimeter wide trace of 1 ounce copper has a resistance of approximately 100 mΩ at room temperature; at a load current of 10 mA, this can introduce a full millivolt of error. In an ideal board layout, the reference should be mounted as close to the load as possible to minimize the length of the output traces, and, therefore, the error introduced by voltage drop. However, in applications where this is not possible or convenient, force and sense connections (sometimes referred to as Kelvin sensing connections) are provided as a means of minimizing the IR drop and improving accuracy. Kelvin connections work by providing a set of high impedance voltage-sensing lines to the output and ground nodes. Because very little current flows through these connections, the IR drop across their traces is negligible, and the output and ground voltages can be sensed very accurately. These voltages are fed SHUTDOWN/ENABLE FEATURE The ADR3425/ADR3450 references can be switched to a lowpower shutdown mode when a voltage of 0.7 V or lower is input to the ENABLE pin. Likewise, the reference becomes operational for ENABLE voltages of 0.85 × VIN or higher. During shutdown, the supply current drops to less than 5 μA, useful in applications that are sensitive to power consumption. If using the shutdown feature, ensure that the ENABLE pin voltage does not fall between 0.7 V and 0.85 × VIN because this causes a large increase in the supply current of the device and may keep the reference from starting up correctly (see Figure 34). If not using the shutdown feature, however, the ENABLE pin can simply be tied to the VIN pin, and the reference remains operational continuously. Rev. 0 | Page 15 of 20 ADR3425/ADR3450 SAMPLE APPLICATIONS Negative Reference Figure 42 shows how to connect the ADR3425/ADR3450 and a standard CMOS op amp, such as the AD8663, to provide a negative reference voltage. This configuration provides two main advantages: first, it only requires two devices and, therefore, does not require excessive board space; second, and more importantly, it does not require any external resistors, meaning the performance of this circuit does not rely on choosing expensive parts with low temperature coefficients to ensure accuracy. +VDD 1µF 0.1µF VIN 4V IN VOUT FORCE 6 R1 10kΩ 0.1µF R2 10kΩ +5V 3 ENABLE V 5 OUT SENSE 1µF 0.1µF ADR3450 GND SENSE 2 GND FORCE 1 +15V ADA4000-1 R3 5kΩ –5V –15V Figure 43. Bipolar Output Reference 4V IN VOUT FORCE 6 AD8663 –5V 0.1µF –VDD 0.1µF 08440-049 Boosted Output Current Reference Figure 44 shows a configuration for obtaining higher current drive capability from the ADR3425/ADR3450 references without sacrificing accuracy. The op amp regulates the current flow through the MOSFET until VOUT equals the output voltage of the reference; current is then drawn directly from VIN instead of from the reference itself, allowing increased current drive capability. VIN 3 ENABLE V 5 OUT SENSE ADR3450 GND SENSE 2 GND FORCE 1 Figure 42. ADR3450 Negative Reference In this configuration, the VOUT pins of the reference sit at virtual ground, and the negative reference voltage and load current are taken directly from the output of the operational amplifier. Note that in applications where the negative supply voltage is close to the reference output voltage, a dual-supply, low offset, rail-torail output amplifier must be used to ensure an accurate output voltage. The operational amplifier must also be able to source or sink an appropriate amount of current for the application. U6 4V IN +16V R1 100Ω 2N7002 VOUT CL 0.1µF 08440-051 VOUT FORCE 6 3 ENABLE V 5 OUT SENSE AD8663 1µF 0.1µF ADR3450 0.1µF RL 200Ω Bipolar Output Reference Figure 43 shows a bipolar reference configuration. By connecting the output of the ADR3425/ADR3450 to the inverting terminal of an operational amplifier, it is possible to obtain both positive and negative reference voltages. R1 and R2 must be matched as closely as possible to ensure minimal difference between the negative and positive outputs. Resistors with low temperature coefficients must also be used if the circuit is used in environments with large temperature swings; otherwise, a voltage difference develops between the two outputs as the ambient temperature changes. GND SENSE 2 GND FORCE 1 Figure 44. Boosted Output Current Reference Because the current-sourcing capability of this circuit depends only on the ID rating of MOSFET, the output drive capability can be adjusted to the application simply by choosing an appropriate MOSFET. In all cases, the VOUT SENSE pin should be tied directly to the load device to maintain maximum output voltage accuracy. Rev. 0 | Page 16 of 20 08440-050 ADR3425/ADR3450 OUTLINE DIMENSIONS 3.00 2.90 2.80 1.70 1.60 1.50 PIN 1 INDICATOR 6 5 4 3.00 2.80 2.60 1 2 3 0.95 BSC 1.90 BSC 1.30 1.15 0.90 1.45 MAX 0.95 MIN 0.20 MAX 0.08 MIN 10° 4° 0° 0.55 0.45 0.35 121608-A 0.15 MAX 0.05 MIN 0.50 MAX 0.30 MIN SEATING PLANE 0.60 BSC COMPLIANT TO JEDEC STANDARDS MO-178-AB Figure 45. 6-Lead Small Outline Transistor Package (SOT-23) (RJ-6) Dimensions shown in millimeters ORDERING GUIDE Model 1 ADR3425ARJZ-R2 ADR3425ARJZ-R7 ADR3450ARJZ-R2 ADR3450ARJZ-R7 1 Output Voltage (V) 2.500 2.500 5.000 5.000 Temperature Range −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C Package Description 6-Lead SOT-23 6-Lead SOT-23 6-Lead SOT-23 6-Lead SOT-23 Package Option RJ-6 RJ-6 RJ-6 RJ-6 Ordering Quantity 250 3,000 250 3,000 Branding R2X R2X R34 R34 Z = RoHS Compliant Part. Rev. 0 | Page 17 of 20 ADR3425/ADR3450 NOTES Rev. 0 | Page 18 of 20 ADR3425/ADR3450 NOTES Rev. 0 | Page 19 of 20 ADR3425/ADR3450 NOTES ©2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D08440-0-3/10(0) Rev. 0 | Page 20 of 20