Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifier AD8628/AD8629/AD8630 Automotive sensors Pressure and position sensors Strain gage amplifiers Medical instrumentation Thermocouple amplifiers Precision current sensing Photodiode amplifier GENERAL DESCRIPTION This amplifier has ultralow offset, drift, and bias current. The AD8628/AD8629/AD8630 are wide bandwidth auto-zero amplifiers featuring rail-to-rail input and output swing and low noise. Operation is fully specified from 2.7 V to 5 V single supply (±1.35 V to ±2.5 V dual supply). The AD8628/AD8629/AD8630 provide benefits previously found only in expensive auto-zeroing or chopper-stabilized amplifiers. Using Analog Devices, Inc., topology, these zerodrift amplifiers combine low cost with high accuracy and low noise. No external capacitor is required. In addition, the AD8628/AD8629/AD8630 greatly reduce the digital switching noise found in most chopper-stabilized amplifiers. With an offset voltage of only 1 μV, drift of less than 0.005 μV/°C, and noise of only 0.5 μV p-p (0 Hz to 10 Hz), the AD8628/ AD8629/AD8630 are suited for applications in which error sources cannot be tolerated. Position and pressure sensors, medical equipment, and strain gage amplifiers benefit greatly from nearly zero drift over their operating temperature range. Many systems can take advantage of the rail-to-rail input and output swings provided by the AD8628/AD8629/AD8630 to reduce input biasing complexity and maximize SNR. V– 2 AD8628 5 V+ 4 –IN TOP VIEW (Not to Scale) +IN 3 02735-001 OUT 1 Figure 1. 5-Lead TSOT (UJ-5) and 5-Lead SOT-23 (RJ-5) NC 1 –IN 2 AD8628 8 NC 7 V+ +IN 3 6 OUT TOP VIEW V– 4 (Not to Scale) 5 NC NC = NO CONNECT 02735-002 APPLICATIONS PIN CONFIGURATIONS Figure 2. 8-Lead SOIC_N (R-8) OUT A 1 –IN A 2 8 AD8629 V+ OUT B TOP VIEW 6 –IN B (Not to Scale) 5 +IN B V– 4 7 +IN A 3 02735-063 Lowest auto-zero amplifier noise Low offset voltage: 1 μV Input offset drift: 0.002 μV/°C Rail-to-rail input and output swing 5 V single-supply operation High gain, CMRR, and PSRR: 120 dB Very low input bias current: 100 pA maximum Low supply current: 1.0 mA Overload recovery time: 10 μs No external components required Figure 3. 8-Lead SOIC_N (R-8) and 8-Lead MSOP (RM-8) 14 OUT D OUT A 1 –IN A 2 +IN A 3 13 –IN D AD8630 12 +IN D TOP VIEW 11 V– (Not to Scale) 10 +IN C +IN B 5 V+ 4 –IN B 6 9 –IN C OUT B 7 8 OUT C 02735-066 FEATURES Figure 4. 14-Lead SOIC_N (R-14) and 14-Lead TSSOP (RU-14) The AD8628/AD8629/AD8630 are specified for the extended industrial temperature range (−40°C to +125°C). The AD8628 is available in tiny 5-lead TSOT, 5-lead SOT-23, and 8-lead narrow SOIC plastic packages. The AD8629 is available in the standard 8-lead narrow SOIC and MSOP plastic packages. The AD8630 quad amplifier is available in 14-lead narrow SOIC and 14-lead TSSOP plastic packages. Rev. F 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 ©2002–2008 Analog Devices, Inc. All rights reserved. AD8628/AD8629/AD8630 TABLE OF CONTENTS Features .............................................................................................. 1 Peak-to-Peak Noise .................................................................... 15 Applications ....................................................................................... 1 Noise Behavior with First-Order Low-Pass Filter .................. 15 General Description ......................................................................... 1 Pin Configurations ........................................................................... 1 Total Integrated Input-Referred Noise for First-Order Filter ........................................................................ 15 Revision History ............................................................................... 2 Input Overvoltage Protection ................................................... 16 Specifications..................................................................................... 3 Output Phase Reversal ............................................................... 16 Electrical Characteristics—VS = 5.0 V ....................................... 3 Overload Recovery Time .......................................................... 16 Electrical Characteristics—VS = 2.7 V ....................................... 4 Infrared Sensors.......................................................................... 17 Absolute Maximum Ratings............................................................ 5 Precision Current Shunt Sensor ............................................... 18 ESD Caution .................................................................................. 5 Output Amplifier for High Precision DACs ........................... 18 Typical Performance Characteristics ............................................. 6 Outline Dimensions ....................................................................... 19 Functional Description .................................................................. 14 Ordering Guide .......................................................................... 20 1/f Noise ....................................................................................... 14 REVISION HISTORY 2/08—Rev. E to Rev. F Renamed TSOT-23 to TSOT ............................................ Universal Deleted Figure 4 and Figure 6 ......................................................... 1 Changes to Figure 3 and Figure 4 Captions .................................. 1 Changes to Table 1 ............................................................................ 3 Changes to Table 2 ............................................................................ 4 Changes to Table 4 ............................................................................ 5 Updated Outline Dimensions ....................................................... 19 Changes to Ordering Guide .......................................................... 20 5/05—Rev. D to Rev. E Changes to Ordering Guide .......................................................... 22 1/05—Rev. C to Rev. D Added AD8630 ................................................................... Universal Added Figure 5 and Figure 6 ........................................................... 1 Changes to Caption in Figure 8 and Figure 9 ............................... 7 Changes to Caption in Figure 14 .................................................... 8 Changes to Figure 17 ........................................................................ 8 Changes to Figure 23 and Figure 24 ............................................... 9 Changes to Figure 25 and Figure 26 ............................................. 10 Changes to Figure 31 ...................................................................... 11 Changes to Figure 40, Figure 41, Figure 42 ................................. 12 Changes to Figure 43 and Figure 44 ............................................. 13 Changes to Figure 51 ...................................................................... 15 Updated Outline Dimensions ....................................................... 20 Changes to Ordering Guide .......................................................... 22 10/04—Rev. B to Rev. C Updated Formatting ........................................................... Universal Added AD8629 ................................................................... Universal Added SOIC and MSOP Pin Configurations ................................1 Added Figure 48 ............................................................................. 13 Changes to Figure 62...................................................................... 17 Added MSOP Package ................................................................... 19 Changes to Ordering Guide .......................................................... 22 10/03—Rev. A to Rev. B Changes to General Description .....................................................1 Changes to Absolute Maximum Ratings ........................................4 Changes to Ordering Guide .............................................................4 Added TSOT-23 Package .............................................................. 15 6/03—Rev. 0 to Rev. A Changes to Specifications .................................................................3 Changes to Ordering Guide .............................................................4 Change to Functional Description ............................................... 10 Updated Outline Dimensions ....................................................... 15 10/02—Revision 0: Initial Version Rev. F | Page 2 of 20 AD8628/AD8629/AD8630 SPECIFICATIONS ELECTRICAL CHARACTERISTICS—VS = 5.0 V VS = 5.0 V, VCM = 2.5 V, TA = 25°C, unless otherwise noted. Table 1. Parameter INPUT CHARACTERISTICS Offset Voltage Symbol Conditions Min VOS Typ Max Unit 1 5 10 μV μV 30 100 100 300 1.5 200 250 5 pA pA nA pA pA V dB dB dB dB μV/°C −40°C ≤ TA ≤ +125°C Input Bias Current AD8628/AD8629 AD8630 IB Input Offset Current IOS −40°C ≤ TA ≤ +125°C 50 −40°C ≤ TA ≤ +125°C Input Voltage Range Common-Mode Rejection Ratio CMRR Large Signal Voltage Gain AVO Offset Voltage Drift OUTPUT CHARACTERISTICS Output Voltage High ∆VOS/∆T VOH Output Voltage Low VOL Short-Circuit Limit ISC VCM = 0 V to 5 V −40°C ≤ TA ≤ +125°C RL = 10 kΩ, VO = 0.3 V to 4.7 V −40°C ≤ TA ≤ +125°C −40°C ≤ TA ≤ +125°C RL = 100 kΩ to ground −40°C ≤ TA ≤ +125°C RL = 10 kΩ to ground −40°C ≤ TA ≤ +125°C RL = 100 kΩ to V+ −40°C ≤ TA ≤ +125°C RL = 10 kΩ to V+ −40°C ≤ TA ≤ +125°C 0 120 115 125 120 4.99 4.99 4.95 4.95 ±25 −40°C ≤ TA ≤ +125°C Output Current IO −40°C ≤ TA ≤ +125°C POWER SUPPLY Power Supply Rejection Ratio PSRR Supply Current/Amplifier ISY INPUT CAPACITANCE Differential Common-Mode DYNAMIC PERFORMANCE Slew Rate Overload Recovery Time Gain Bandwidth Product NOISE PERFORMANCE Voltage Noise CIN Voltage Noise Density Current Noise Density en in SR VS = 2.7 V to 5.5 V −40°C ≤ TA ≤ +125°C VO = VS/2 −40°C ≤ TA ≤ +125°C 4.996 4.995 4.98 4.97 1 2 10 15 ±50 ±40 ±30 ±15 130 0.85 1.0 0.02 5 5 20 20 1.1 1.2 V V V V mV mV mV mV mA mA mA mA dB mA mA 1.5 8.0 pF pF RL = 10 kΩ 1.0 0.05 2.5 V/μs ms MHz 0.1 Hz to 10 Hz 0.1 Hz to 1.0 Hz f = 1 kHz f = 10 Hz 0.5 0.16 22 5 μV p-p μV p-p nV/√Hz fA/√Hz GBP en p-p 115 140 130 145 135 0.002 Rev. F | Page 3 of 20 AD8628/AD8629/AD8630 ELECTRICAL CHARACTERISTICS—VS = 2.7 V VS = 2.7 V, VCM = 1.35 V, VO = 1.4 V, TA = 25°C, unless otherwise noted. Table 2. Parameter INPUT CHARACTERISTICS Offset Voltage Symbol Conditions Min VOS Typ Max Unit 1 5 10 μV μV 30 100 1.0 50 100 300 1.5 200 250 2.7 pA pA nA pA pA V dB dB dB dB μV/°C −40°C ≤ TA ≤ +125°C Input Bias Current AD8628/AD8629 AD8630 IB Input Offset Current IOS −40°C ≤ TA ≤ +125°C −40°C ≤ TA ≤ +125°C Input Voltage Range Common-Mode Rejection Ratio CMRR Large Signal Voltage Gain AVO Offset Voltage Drift OUTPUT CHARACTERISTICS Output Voltage High ∆VOS/∆T VOH Output Voltage Low VOL Short-Circuit Limit ISC VCM = 0 V to 2.7 V −40°C ≤ TA ≤ +125°C RL = 10 kΩ, VO = 0.3 V to 2.4 V −40°C ≤ TA ≤ +125°C −40°C ≤ TA ≤ +125°C RL = 100 kΩ to ground −40°C ≤ TA ≤ +125°C RL = 10 kΩ to ground −40°C ≤ TA ≤ +125°C RL = 100 kΩ to V+ −40°C ≤ TA ≤ +125°C RL = 10 kΩ to V+ −40°C ≤ TA ≤ +125°C 0 115 110 110 105 2.68 2.68 2.67 2.67 ±10 −40°C ≤ TA ≤ +125°C Output Current IO −40°C ≤ TA ≤ +125°C POWER SUPPLY Power Supply Rejection Ratio PSRR Supply Current/Amplifier ISY INPUT CAPACITANCE Differential Common-Mode DYNAMIC PERFORMANCE Slew Rate Overload Recovery Time Gain Bandwidth Product NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density CIN SR VS = 2.7 V to 5.5 V −40°C ≤ TA ≤ +125°C VO = VS/2 −40°C ≤ TA ≤ +125°C 2.695 2.695 2.68 2.675 1 2 10 15 ±15 ±10 ±10 ±5 130 0.75 0.9 0.02 5 5 20 20 1.0 1.2 V V V V mV mV mV mV mA mA mA mA dB mA mA 1.5 8.0 pF pF RL = 10 kΩ 1 0.05 2 V/μs ms MHz 0.1 Hz to 10 Hz f = 1 kHz f = 10 Hz 0.5 22 5 μV p-p nV/√Hz fA/√Hz GBP en p-p en in 115 130 120 140 130 0.002 Rev. F | Page 4 of 20 AD8628/AD8629/AD8630 ABSOLUTE MAXIMUM RATINGS Table 4. Thermal Characteristics Table 3. Parameters Supply Voltage Input Voltage Differential Input Voltage1 Output Short-Circuit Duration to GND Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature (Soldering, 60 sec) 1 Ratings 6V GND − 0.3 V to VS + 0.3 V ±5.0 V Indefinite −65°C to +150°C −40°C to +125°C −65°C to +150°C 300°C Package Type 5-Lead TSOT (UJ-5) 5-Lead SOT-23 (RJ-5) 8-Lead SOIC_N (R-8) 8-Lead MSOP (RM-8) 14-Lead SOIC_N (R-14) 14-Lead TSSOP (RU-14) 1 θJC 61 146 43 44 43 23 Unit °C/W °C/W °C/W °C/W °C/W °C/W θJA is specified for worst-case conditions, that is, θJA is specified for the device soldered in a circuit board for surface-mount packages. This was measured using a standard 2-layer board. Differential input voltage is limited to ±5 V or the supply voltage, whichever is less. 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. θJA1 207 230 158 190 105 148 ESD CAUTION Rev. F | Page 5 of 20 AD8628/AD8629/AD8630 TYPICAL PERFORMANCE CHARACTERISTICS 100 VS = 5V VCM = 2.5V TA = 25°C 90 80 NUMBER OF AMPLIFIERS 140 120 100 80 60 70 60 50 40 30 40 20 20 10 0 –2.5 –1.5 –0.5 0.5 INPUT OFFSET VOLTAGE (µV) 1.5 2.5 0 –2.5 02735-003 –1.5 Figure 5. Input Offset Voltage Distribution +85°C NUMBER OF AMPLIFIERS 30 +25°C 10 0 1 2 3 4 5 INPUT COMMON-MODE VOLTAGE (V) 10 1 10 5 4 3 2 1 –40°C 6 0 02735-004 INPUT BIAS CURRENT (pA) 40 20 VS = 5V TA = –40°C TO +125°C 6 50 0 2 Figure 6. AD8628 Input Bias Current vs. Input Common-Mode Voltage 1k VS = 5V 4 6 TCVOS (nV/°C) Figure 9. Input Offset Voltage Drift 1500 150°C 1000 VS = 5V TA = 25°C 100 125°C OUTPUT VOLTAGE (mV) INPUT BIAS CURRENT (pA) 8 7 VS = 5V 500 0 –500 10 SOURCE SINK 1 0.1 –1000 0 1 2 3 4 5 INPUT COMMON-MODE VOLTAGE (V) 6 0.01 0.0001 02735-005 –1500 2.5 1.5 Figure 8. Input Offset Voltage Distribution 60 0 –0.5 0.5 INPUT OFFSET VOLTAGE (µV) Figure 7. AD8628 Input Bias Current vs. Input Common-Mode Voltage at 5 V Rev. F | Page 6 of 20 0.001 0.01 0.1 LOAD CURRENT (mA) Figure 10. Output Voltage to Supply Rail vs. Load Current 02735-008 NUMBER OF AMPLIFIERS 160 02735-006 VS = 2.7V TA = 25°C 02735-007 180 AD8628/AD8629/AD8630 1k 1000 TA = 25°C VS = 2.7V 800 SUPPLY CURRENT (µA) 10 SOURCE SINK 1 0.1 600 400 0.01 0.1 LOAD CURRENT (mA) 1 10 0 Figure 11. Output Voltage to Supply Rail vs. Load Current 0 1 2 3 4 SUPPLY VOLTAGE (V) VS = 5V VCM = 2.5V TA = –40°C TO +150°C OPEN-LOOP GAIN (dB) 900 450 GAIN 40 0 45 20 PHASE 90 135 180 0 –25 0 25 50 75 100 TEMPERATURE (°C) 125 150 175 02735-010 0 –50 10k Figure 12. AD8628 Input Bias Current vs. Temperature 100k 1M FREQUENCY (Hz) 02735-013 225 10M Figure 15. Open-Loop Gain and Phase vs. Frequency 1250 70 TA = 25 °C VS = 5V CL = 20pF RL = ∞ ΦM = 52.1° 60 5V 1000 OPEN-LOOP GAIN (dB) 50 2.7V 750 500 250 GAIN 0 40 45 30 PHASE 20 90 10 135 0 180 –10 225 PHASE SHIFT (Degrees) INPUT BIAS CURRENT (pA) VS = 2.7V CL = 20pF RL = ∞ ФM = 45° 60 100 –20 0 –50 0 50 100 TEMPERATURE (°C) 150 200 02735-011 SUPPLY CURRENT (µA) 6 Figure 14. Supply Current vs. Supply Voltage 1500 1150 5 PHASE SHIFT (Degrees) 0.001 02735-009 0.01 0.0001 02735-012 200 Figure 13. Supply Current vs. Temperature –30 10k 100k 1M FREQUENCY (Hz) 10M Figure 16. Open-Loop Gain and Phase vs. Frequency Rev. F | Page 7 of 20 02735-014 OUTPUT VOLTAGE (mV) 100 AD8628/AD8629/AD8630 70 300 VS = 2.7V CL = 20pF RL = 2kΩ 240 30 OUTPUT IMPEDANCE (Ω) AV = 100 40 AV = 10 20 10 AV = 1 0 210 120 90 –20 30 10k 100k 1M FREQUENCY (Hz) 10M AV = 100 150 60 –30 1k AV = 1 180 –10 0 100 02735-015 CLOSED-LOOP GAIN (dB) 50 VS = 5V 270 Figure 17. Closed-Loop Gain vs. Frequency AV = 10 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M Figure 20. Output Impedance vs. Frequency 70 VS = 5V CL = 20pF RL = 2kΩ 60 AV = 100 40 30 VOLTAGE (500mV/DIV) CLOSED-LOOP GAIN (dB) 50 AV = 10 20 10 AV = 1 0 0V VS = ±1.35V CL = 300pF RL = ∞ AV = 1 –10 10k 100k 1M FREQUENCY (Hz) 10M TIME (4µs/DIV) 02735-019 –30 1k 02735-016 –20 Figure 21. Large Signal Transient Response Figure 18. Closed-Loop Gain vs. Frequency 300 270 VS = 2.7V 180 VOLTAGE (1V/DIV) AV = 1 210 AV = 100 150 120 0V VS = ±2.5V CL = 300pF RL = ∞ AV = 1 90 AV = 10 60 0 100 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M TIME (5µs/DIV) Figure 22. Large Signal Transient Response Figure 19. Output Impedance vs. Frequency Rev. F | Page 8 of 20 02735-020 30 02735-017 OUTPUT IMPEDANCE (Ω) 240 02735-018 60 AD8628/AD8629/AD8630 80 VS = ±2.5V RL = 2kΩ TA = 25°C 70 60 OVERSHOOT (%) VOLTAGE (50mV/DIV) VS = ±1.35V CL = 50pF RL = ∞ AV = 1 0V 50 40 30 OS– 20 OS+ TIME (4µs/DIV) 0 1k 10 100 CAPACITIVE LOAD (pF) Figure 26. Small Signal Overshoot vs. Load Capacitance Figure 23. Small Signal Transient Response VS = ±2.5V CL = 50pF RL = ∞ AV = 1 VS = ±2.5V AV = –50 RL = 10kΩ CL = 0pF CH1 = 50mV/DIV CH2 = 1V/DIV VIN VOLTAGE (V) VOLTAGE (50mV/DIV) 1 02735-024 02735-021 10 0V 0V 0V TIME (4µs/DIV) 02735-025 02735-022 VOUT TIME (2µs/DIV) Figure 27. Positive Overvoltage Recovery Figure 24. Small Signal Transient Response 100 VS = ±1.35V RL = 2kΩ TA = 25°C 90 0V VS = ±2.5V AV = –50 RL = 10kΩ CL = 0pF CH1 = 50mV/DIV CH2 = 1V/DIV 80 VOLTAGE (V) 60 OS– 50 40 VIN VOUT OS+ 30 20 0 1 10 100 CAPACITIVE LOAD (pF) 1k TIME (10µs/DIV) Figure 25. Small Signal Overshoot vs. Load Capacitance Figure 28. Negative Overvoltage Recovery Rev. F | Page 9 of 20 02735-026 0V 10 02735-023 OVERSHOOT (%) 70 AD8628/AD8629/AD8630 140 VS = ±1.35V 120 100 80 PSRR (dB) VOLTAGE (1V/DIV) VS = ±2.5V VIN = 1kHz @ ±3V p-p CL = 0pF RL = 10kΩ AV = 1 0V 60 +PSRR 40 20 –PSRR 0 –20 TIME (200µs/DIV) –60 100 140 140 100 80 80 60 60 10M 1M 10M VS = ±2.5V 40 20 0 –20 –20 –40 –40 10k 100k FREQUENCY (Hz) 1M 10M –PSRR 20 0 1k +PSRR 40 –60 100 1k 10k 100k FREQUENCY (Hz) Figure 33. PSRR vs. Frequency Figure 30. CMRR vs. Frequency 3.0 VS = 5V VS = 2.7V RL = 10kΩ TA = 25°C AV = 1 120 2.5 OUTPUT SWING (V p-p) 100 80 60 40 20 0 –20 2.0 1.5 1.0 0.5 –60 100 1k 10k 100k FREQUENCY (Hz) 1M 10M 0 100 1k 10k FREQUENCY (Hz) 100k Figure 34. Maximum Output Swing vs. Frequency Figure 31. CMRR vs. Frequency Rev. F | Page 10 of 20 1M 02735-032 –40 02735-029 CMRR (dB) 02735-031 PSRR (dB) 100 140 1M 120 02735-028 CMRR (dB) VS = 2.7V –60 100 10k 100k FREQUENCY (Hz) Figure 32. PSRR vs. Frequency Figure 29. No Phase Reversal 120 1k 02735-030 02735-027 –40 AD8628/AD8629/AD8630 VOLTAGE NOISE DENSITY (nV/√Hz) 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 1k 10k FREQUENCY (Hz) 100k 1M 90 75 60 45 30 15 0 02735-033 0 100 Figure 35. Maximum Output Swing vs. Frequency VS = 2.7V NOISE AT 1kHz = 21.3nV 105 0 0.30 VOLTAGE (µV) 2.5 0.15 0 –0.15 –0.30 0 1 2 3 4 5 6 TIME (µs) 7 8 9 10 90 75 60 45 30 15 0 02735-034 –0.45 Figure 36. 0.1 Hz to 10 Hz Noise VS = 2.7V NOISE AT 10kHz = 42.4nV 105 0 5 10 15 FREQUENCY (kHz) 25 02735-037 VOLTAGE NOISE DENSITY (nV/√Hz) 0.45 2.5 20 Figure 39. Voltage Noise Density at 2.7 V from 0 Hz to 25 kHz 0.60 120 VS = 5V VOLTAGE NOISE DENSITY (nV/√Hz) 0.45 0.30 0.15 0 –0.15 –0.30 –0.45 0 1 2 3 4 5 6 TIME (µs) 7 8 9 10 02735-035 VOLTAGE (µV) 2.0 120 VS = 2.7V –0.60 1.0 1.5 FREQUENCY (kHz) Figure 38. Voltage Noise Density at 2.7 V from 0 Hz to 2.5 kHz 0.60 –0.60 0.5 02735-038 OUTPUT SWING (V p-p) 120 VS = 5V RL = 10kΩ TA = 25°C AV = 1 5.0 02735-036 5.5 Figure 37. 0.1 Hz to 10 Hz Noise VS = 5V NOISE AT 1kHz = 22.1nV 105 90 75 60 45 30 15 0 0 0.5 1.0 1.5 FREQUENCY (kHz) 2.0 Figure 40. Voltage Noise Density at 5 V from 0 Hz to 2.5 kHz Rev. F | Page 11 of 20 AD8628/AD8629/AD8630 150 90 75 60 45 30 15 0 5 10 15 FREQUENCY (kHz) 20 25 ISC– 0 ISC+ –50 0 25 50 75 100 TEMPERATURE (°C) 125 150 175 150 105 90 75 60 45 30 0 10 5 FREQUENCY (kHz) 100 ISC– 50 0 –50 ISC+ –100 –50 02735-040 15 VS = 5V TA = –40°C TO +150°C Figure 42. Voltage Noise Density –25 0 25 50 75 100 TEMPERATURE (°C) 125 150 175 02735-043 OUTPUT SHORT-CIRCUIT CURRENT (mA) VS = 5V 175 Figure 45. Output Short-Circuit Current vs. Temperature 150 1k VS = 5V OUTPUT-TO-RAIL VOLTAGE (mV) 140 130 VS = 2.7V TO 5V TA = –40°C TO +125°C 120 110 100 90 80 70 VCC – VOH @ 1kΩ 100 VOL – VEE @ 1kΩ VCC – VOH @ 10kΩ 10 VOL – VEE @ 10kΩ VCC – VOH @ 100kΩ 1 VOL – VEE @ 100kΩ 60 50 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 125 02735-041 POWER SUPPLY REJECTION (dB) –25 Figure 44. Output Short-Circuit Current vs. Temperature 120 VOLTAGE NOISE DENSITY (nV/√Hz) 50 –100 –50 Figure 41. Voltage Noise Density at 5 V from 0 Hz to 25 kHz 0 100 02735-044 0 VS = 2.7V TA = –40°C TO +150°C 02735-042 105 OUTPUT SHORT-CIRCUIT CURRENT (mA) VS = 5V NOISE AT 10kHz = 36.4nV 02735-039 VOLTAGE NOISE DENSITY (nV/√Hz) 120 Figure 43. Power Supply Rejection vs. Temperature 0.1 –50 –25 0 25 50 75 100 TEMPERATURE (°C) 125 150 Figure 46. Output-to-Rail Voltage vs. Temperature Rev. F | Page 12 of 20 AD8628/AD8629/AD8630 1k 140 VS = ±2.5V 120 CHANNEL SEPARATION (dB) VCC – VOH @ 1kΩ 100 VOL – VEE @ 1kΩ VCC – VOH @ 10kΩ 10 VOL – VEE @ 10kΩ VCC – VOH @ 100kΩ 1 VOL – VEE @ 100kΩ 100 80 60 40 R1 10kΩ +2.5V VIN 28mV p-p + – 20 V+ A V– V– VOUT R2 100Ω B V+ –25 0 25 50 75 100 TEMPERATURE (°C) 125 150 175 Figure 47. Output-to-Rail Voltage vs. Temperature 0 1k 10k 100k FREQUENCY (Hz) 1M Figure 48. AD8629/AD8630 Channel Separation Rev. F | Page 13 of 20 10M 02735-062 –2.5V 0.1 –50 02735-045 OUTPUT-TO-RAIL VOLTAGE (mV) VS = 2.7V AD8628/AD8629/AD8630 FUNCTIONAL DESCRIPTION Previous designs used either auto-zeroing or chopping to add precision to the specifications of an amplifier. Auto-zeroing results in low noise energy at the auto-zeroing frequency, at the expense of higher low frequency noise due to aliasing of wideband noise into the auto-zeroed frequency band. Chopping results in lower low frequency noise at the expense of larger noise energy at the chopping frequency. The AD8628/AD8629/ AD8630 family uses both auto-zeroing and chopping in a patented ping-pong arrangement to obtain lower low frequency noise together with lower energy at the chopping and auto-zeroing frequencies, maximizing the signal-to-noise ratio for the majority of applications without the need for additional filtering. The relatively high clock frequency of 15 kHz simplifies filter requirements for a wide, useful, noise-free bandwidth. The AD8628 is among the few auto-zero amplifiers offered in the 5-lead TSOT package. This provides a significant improvement over the ac parameters of the previous auto-zero amplifiers. The AD8628/AD8629/AD8630 have low noise over a relatively wide bandwidth (0 Hz to 10 kHz) and can be used where the highest dc precision is required. In systems with signal bandwidths of from 5 kHz to 10 kHz, the AD8628/ AD8629/AD8630 provide true 16-bit accuracy, making them the best choice for very high resolution systems. 1/f noise, also known as pink noise, is a major contributor to errors in dc-coupled measurements. This 1/f noise error term can be in the range of several μV or more, and, when amplified with the closed-loop gain of the circuit, can show up as a large output offset. For example, when an amplifier with a 5 μV p-p 1/f noise is configured for a gain of 1000, its output has 5 mV of error due to the 1/f noise. However, the AD8628/AD8629/ AD8630 eliminate 1/f noise internally, thereby greatly reducing output errors. The internal elimination of 1/f noise is accomplished as follows. 1/f noise appears as a slowly varying offset to AD8628/AD8629/ AD8630 inputs. Auto-zeroing corrects any dc or low frequency offset. Therefore, the 1/f noise component is essentially removed, leaving the AD8628/AD8629/AD8630 free of 1/f noise. One of the biggest advantages that the AD8628/AD8629/AD8630 bring to systems applications over competitive auto-zero amplifiers is their very low noise. The comparison shown in Figure 49 indicates an input-referred noise density of 19.4 nV/√Hz at 1 kHz for the AD8628, which is much better than the LTC2050 and LMC2001. The noise is flat from dc to 1.5 kHz, slowly increasing up to 20 kHz. The lower noise at low frequency is desirable where auto-zero amplifiers are widely used. 120 Rev. F | Page 14 of 20 LTC2050 (89.7nV/√Hz) 105 90 75 60 LMC2001 (31.1nV/√Hz) 45 30 15 0 AD8628 (19.4nV/√Hz) 0 2 MK AT 1kHz FOR ALL 3 GRAPHS 4 6 FREQUENCY (kHz) 8 10 Figure 49. Noise Spectral Density of AD8628 vs. Competition 12 02735-046 The AD8628/AD8629/AD8630 achieve a high degree of precision through a patented combination of auto-zeroing and chopping. This unique topology allows the AD8628/ AD8629/ AD8630 to maintain their low offset voltage over a wide temperature range and over their operating lifetime. The AD8628/AD8629/AD8630 also optimize the noise and bandwidth over previous generations of auto-zero amplifiers, offering the lowest voltage noise of any auto-zero amplifier by more than 50%. 1/f NOISE VOLTAGE NOISE DENSITY (nV/√Hz) The AD8628/AD8629/AD8630 are single-supply, ultrahigh precision rail-to-rail input and output operational amplifiers. The typical offset voltage of less than 1 μV allows these amplifiers to be easily configured for high gains without risk of excessive output voltage errors. The extremely small temperature drift of 2 nV/°C ensures a minimum offset voltage error over their entire temperature range of −40°C to +125°C, making these amplifiers ideal for a variety of sensitive measurement applications in harsh operating environments. AD8628/AD8629/AD8630 50 PEAK-TO-PEAK NOISE 45 Because of the ping-pong action between auto-zeroing and chopping, the peak-to-peak noise of the AD8628/AD8629/ AD8630 is much lower than the competition. Figure 50 and Figure 51 show this comparison. 40 NOISE (dB) 35 en p-p = 0.5µV BW = 0.1Hz TO 10Hz 30 25 20 VOLTAGE (0.5µV/DIV) 15 10 0 0 10 20 30 40 50 60 70 FREQUENCY (kHz) 80 90 100 02735-050 5 Figure 53. Simulation Transfer Function of the Test Circuit 02735-047 50 TIME (1s/DIV) 45 40 Figure 50. AD8628 Peak-to-Peak Noise NOISE (dB) 35 en p-p = 2.3µV BW = 0.1Hz TO 10Hz 30 25 20 VOLTAGE (0.5µV/DIV) 15 10 0 0 10 20 30 40 50 60 70 FREQUENCY (kHz) 80 90 100 02735-051 5 Figure 54. Actual Transfer Function of the Test Circuit 02735-048 The measured noise spectrum of the test circuit charted in Figure 54 shows that noise between 5 kHz and 45 kHz is successfully rolled off by the first-order filter. TOTAL INTEGRATED INPUT-REFERRED NOISE FOR FIRST-ORDER FILTER NOISE BEHAVIOR WITH FIRST-ORDER LOW-PASS FILTER For a first-order filter, the total integrated noise from the AD8628 is lower than the LTC2050. The AD8628 was simulated as a low-pass filter (Figure 53) and then configured as shown in Figure 52. The behavior of the AD8628 matches the simulated data. It was verified that noise is rolled off by first-order filtering. Figure 53 and Figure 54 show the difference between the simulated and actual transfer functions of the circuit shown in Figure 52. IN OUT AD8551 AD8628 1 0.1 10 Figure 52. Test Circuit: First-Order Low-Pass Filter, ×101 Gain and 3 kHz Corner Frequency 100 1k 3dB FILTER BANDWIDTH (Hz) Figure 55. 3 dB Filter Bandwidth in Hz Rev. F | Page 15 of 20 10k 02735-052 1kΩ 470pF LTC2050 02735-049 100kΩ 10 RMS NOISE (µV) TIME (1s/DIV) Figure 51. LTC2050 Peak-to-Peak Noise AD8628/AD8629/AD8630 INPUT OVERVOLTAGE PROTECTION VOLTAGE (V) These diodes are connected between the inputs and each supply rail to protect the input transistors against an electrostatic discharge event, and they are normally reverse-biased. However, if the input voltage exceeds the supply voltage, these ESD diodes can become forward-biased. Without current limiting, excessive amounts of current could flow through these diodes, causing permanent damage to the device. If inputs are subject to overvoltage, appropriate series resistors should be inserted to limit the diode current to less than 5 mA maximum. 0V 0V VOUT 02735-053 Although the AD8628/AD8629/AD8630 are rail-to-rail input amplifiers, care should be taken to ensure that the potential difference between the inputs does not exceed the supply voltage. Under normal negative feedback operating conditions, the amplifier corrects its output to ensure that the two inputs are at the same voltage. However, if either input exceeds either supply rail by more than 0.3 V, large currents begin to flow through the ESD protection diodes in the amplifier. CH1 = 50mV/DIV CH2 = 1V/DIV AV = –50 VIN TIME (500µs/DIV) Figure 56. Positive Input Overload Recovery for the AD8628 CH1 = 50mV/DIV CH2 = 1V/DIV AV = –50 VIN 0V 0V TIME (500µs/DIV) Figure 57. Positive Input Overload Recovery for LTC2050 CH1 = 50mV/DIV CH2 = 1V/DIV AV = –50 VIN VOLTAGE (V) OVERLOAD RECOVERY TIME Many auto-zero amplifiers are plagued by a long overload recovery time, often in ms, due to the complicated settling behavior of the internal nulling loops after saturation of the outputs. The AD8628/AD8629/AD8630 have been designed so that internal settling occurs within two clock cycles after output saturation happens. This results in a much shorter recovery time, less than 10 μs, when compared to other autozero amplifiers. The wide bandwidth of the AD8628/AD8629/ AD8630 enhances performance when the parts are used to drive loads that inject transients into the outputs. This is a common situation when an amplifier is used to drive the input of switched capacitor ADCs. 02735-054 VOUT The AD8628/AD8629/AD8630 amplifiers have been carefully designed to prevent any output phase reversal, provided that both inputs are maintained within the supply voltages. If one or both inputs could exceed either supply voltage, a resistor should be placed in series with the input to limit the current to less than 5 mA. This ensures that the output does not reverse its phase. Rev. F | Page 16 of 20 0V 0V VOUT TIME (500µs/DIV) Figure 58. Positive Input Overload Recovery for LMC2001 02735-055 Output phase reversal occurs in some amplifiers when the input common-mode voltage range is exceeded. As common-mode voltage is moved outside of the common-mode range, the outputs of these amplifiers can suddenly jump in the opposite direction to the supply rail. This is the result of the differential input pair shutting down, causing a radical shifting of internal voltages that results in the erratic output behavior. VOLTAGE (V) OUTPUT PHASE REVERSAL AD8628/AD8629/AD8630 VOLTAGE (V) 0V The results shown in Figure 56 to Figure 61 are summarized in Table 5. CH1 = 50mV/DIV CH2 = 1V/DIV AV = –50 Table 5. Overload Recovery Time VIN Product AD8628 LTC2050 LMC2001 VOUT Negative Overload Recovery (μs) 9 25,000 35,000 INFRARED SENSORS 02735-056 0V TIME (500µs/DIV) Figure 59. Negative Input Overload Recovery for the AD8628 0V CH1 = 50mV/DIV CH2 = 1V/DIV AV = –50 VIN VOUT 0V TIME (500µs/DIV) Infrared (IR) sensors, particularly thermopiles, are increasingly being used in temperature measurement for applications as wideranging as automotive climate control, human ear thermometers, home insulation analysis, and automotive repair diagnostics. The relatively small output signal of the sensor demands high gain with very low offset voltage and drift to avoid dc errors. If interstage ac coupling is used, as in Figure 62, low offset and drift prevent the output of the input amplifier from drifting close to saturation. The low input bias currents generate minimal errors from the output impedance of the sensor. As with pressure sensors, the very low amplifier drift with time and temperature eliminate additional errors once the temperature measurement is calibrated. The low 1/f noise improves SNR for dc measurements taken over periods often exceeding one-fifth of a second. 02735-057 VOLTAGE (V) Positive Overload Recovery (μs) 6 650 40,000 Figure 62 shows a circuit that can amplify ac signals from 100 μV to 300 μV up to the 1 V to 3 V levels, with gain of 10,000 for accurate analog-to-digital conversion. 10kΩ 100Ω Figure 60. Negative Input Overload Recovery for LTC2050 100kΩ 100kΩ 5V 5V IR DETECTOR 0V 1/2 AD8629 1/2 AD8629 10kΩ fC ≈ 1.6Hz TO BIAS VOLTAGE VIN Figure 62. AD8629 Used as Preamplifier for Thermopile VOUT 0V TIME (500µs/DIV) 02735-058 VOLTAGE (V) CH1 = 50mV/DIV CH2 = 1V/DIV AV = –50 10µF Figure 61. Negative Input Overload Recovery for LMC2001 Rev. F | Page 17 of 20 02735-059 100µV – 300µV AD8628/AD8629/AD8630 PRECISION CURRENT SHUNT SENSOR OUTPUT AMPLIFIER FOR HIGH PRECISION DACS A precision current shunt sensor benefits from the unique attributes of auto-zero amplifiers when used in a differencing configuration, as shown in Figure 63. Current shunt sensors are used in precision current sources for feedback control systems. They are also used in a variety of other applications, including battery fuel gauging, laser diode power measurement and control, torque feedback controls in electric power steering, and precision power metering. The AD8628/AD8629/AD8360 are used as output amplifiers for a 16-bit high precision DAC in a unipolar configuration. In this case, the selected op amp needs to have very low offset voltage (the DAC LSB is 38 μV when operated with a 2.5 V reference) to eliminate the need for output offset trims. Input bias current (typically a few tens of picoamperes) must also be very low because it generates an additional zero code error when multiplied by the DAC output impedance (approximately 6 kΩ). I 100kΩ e = 1000 RS I 100mV/mA RS 0.1Ω Rail-to-rail input and output provide full-scale output with very little error. Output impedance of the DAC is constant and codeindependent, but the high input impedance of the AD8628/ AD8629/AD8630 minimizes gain errors. The wide bandwidth of the amplifiers also serves well in this case. The amplifiers, with settling time of 1 μs, add another time constant to the system, increasing the settling time of the output. The settling time of the AD5541 is 1 μs. The combined settling time is approximately 1.4 μs, as can be derived from the following equation: RL 100Ω C 5V AD8628 100Ω C 02735-060 100kΩ t S (TOTAL ) = Figure 63. Low-Side Current Sensing In such applications, it is desirable to use a shunt with very low resistance to minimize the series voltage drop; this minimizes wasted power and allows the measurement of high currents while saving power. A typical shunt might be 0.1 Ω. At measured current values of 1 A, the output signal of the shunt is hundreds of millivolts, or even volts, and amplifier error sources are not critical. However, at low measured current values in the 1 mA range, the 100 μV output voltage of the shunt demands a very low offset voltage and drift to maintain absolute accuracy. Low input bias currents are also needed, so that injected bias current does not become a significant percentage of the measured current. High open-loop gain, CMRR, and PSRR help to maintain the overall circuit accuracy. As long as the rate of change of the current is not too fast, an auto-zero amplifier can be used with excellent results. 5V (t S 2.5V VDD 10µF 0.1µF 0.1µF SERIAL INTERFACE DAC )2 + (t S AD8628 )2 REF(REF*) REFS* CS DIN SCLK AD8628 AD5541/AD5542 OUT UNIPOLAR OUTPUT LDAC* DGND AGND *AD5542 ONLY Rev. F | Page 18 of 20 Figure 64. AD8628 Used as an Output Amplifier 02735-061 SUPPLY AD8628/AD8629/AD8630 OUTLINE DIMENSIONS 5.00 (0.1968) 4.80 (0.1890) 2.90 BSC 5 4 2 1.27 (0.0500) BSC 0.95 BSC 0.25 (0.0098) 0.10 (0.0040) 1.90 BSC *1.00 MAX 0.10 MAX 4 6.20 (0.2441) 5.80 (0.2284) 3 PIN 1 *0.90 0.87 0.84 5 1 0.50 0.30 8° 4° 0° SEATING PLANE 0.51 (0.0201) 0.31 (0.0122) COPLANARITY 0.10 SEATING PLANE 0.20 0.08 0.60 0.45 0.30 1.75 (0.0688) 1.35 (0.0532) 0.50 (0.0196) 0.25 (0.0099) 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) COMPLIANT TO JEDEC STANDARDS MS-012-A A 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. *COMPLIANT TO JEDEC STANDARDS MO-193-AB WITH THE EXCEPTION OF PACKAGE HEIGHT AND THICKNESS. Figure 67. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) Figure 65. 5-Lead Thin Small Outline Transistor Package [TSOT] (UJ-5) Dimensions shown in millimeters 3.20 3.00 2.80 2.90 BSC 5 4 2.80 BSC 1.60 BSC 1 2 8 3.20 3.00 2.80 3 1 PIN 1 0.95 BSC 4 0.65 BSC 1.45 MAX 0.15 MAX 5.15 4.90 4.65 PIN 1 1.90 BSC 1.30 1.15 0.90 5 0.50 0.30 SEATING PLANE 0.95 0.85 0.75 0.22 0.08 10° 5° 0° 1.10 MAX 0.15 0.00 0.60 0.45 0.30 0.38 0.22 COPLANARITY 0.10 0.23 0.08 8° 0° SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-178-A A COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 66. 5-Lead Small Outline Transistor Package [SOT-23] (RJ-5) Dimensions shown in millimeters Figure 68. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters Rev. F | Page 19 of 20 45° 8° 0° 0.80 0.60 0.40 012407-A 1 8 4.00 (0.1574) 3.80 (0.1497) 2.80 BSC 1.60 BSC AD8628/AD8629/AD8630 5.10 5.00 4.90 8.75 (0.3445) 8.55 (0.3366) 8 14 1 7 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10 0.51 (0.0201) 0.31 (0.0122) 14 6.20 (0.2441) 5.80 (0.2283) 1.75 (0.0689) 1.35 (0.0531) SEATING PLANE 0.50 (0.0197) 0.25 (0.0098) 6.40 BSC 45° 1 8° 0° 0.25 (0.0098) 0.17 (0.0067) 8 4.50 4.40 4.30 7 PIN 1 COMPLIANT TO JEDEC STANDARDS MS-012-AB 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. 0.65 BSC 1.05 1.00 0.80 1.27 (0.0500) 0.40 (0.0157) 060606-A 4.00 (0.1575) 3.80 (0.1496) 1.20 MAX 0.15 0.05 0.30 0.19 0.20 0.09 SEATING COPLANARITY PLANE 0.10 0.75 0.60 0.45 8° 0° COMPLIANT TO JEDEC STANDARDS MO-153-AB-1 Figure 69. 14-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-14) Dimensions shown in millimeters and (inches) Figure 70. 14-Lead Thin Shrink Small Outline Package [TSSOP] (RU-14) Dimensions shown in millimeters ORDERING GUIDE Model AD8628AUJ-R2 AD8628AUJ-REEL AD8628AUJ-REEL7 AD8628AUJZ-R2 1 AD8628AUJZ-REEL1 AD8628AUJZ-REEL71 AD8628AR AD8628AR-REEL AD8628AR-REEL7 AD8628ARZ1 AD8628ARZ-REEL1 AD8628ARZ-REEL71 AD8628ART-R2 AD8628ART-REEL7 AD8628ARTZ-R21 AD8628ARTZ-REEL71 AD8629ARZ1 AD8629ARZ-REEL1 AD8629ARZ-REEL71 AD8629ARMZ-R21 AD8629ARMZ-REEL1 AD8630ARUZ1 AD8630ARUZ-REEL1 AD8630ARZ1 AD8630ARZ-REEL1 AD8630ARZ-REEL71 1 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 Package Description 5-Lead TSOT 5-Lead TSOT 5-Lead TSOT 5-Lead TSOT 5-Lead TSOT 5-Lead TSOT 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 14-Lead TSSOP 14-Lead TSSOP 14-Lead SOIC_N 14-Lead SOIC_N 14-Lead SOIC_N Z = RoHS Compliant Part. ©2002–2008 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D02735-0-2/08(F) Rev. F | Page 20 of 20 Package Option UJ-5 UJ-5 UJ-5 UJ-5 UJ-5 UJ-5 R-8 R-8 R-8 R-8 R-8 R-8 RJ-5 RJ-5 RJ-5 RJ-5 R-8 R-8 R-8 RM-8 RM-8 RU-14 RU-14 R-14 R-14 R-14 Branding AYB AYB AYB A0L A0L A0L AYA AYA A0L A0L A06 A06