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Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifier AD8628/AD8629/AD8630
FEATURES
Lowest auto-zero amplifier noise Low offset voltage: 1 V Input offset drift: 0.002 V/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 s No external components required
PIN CONFIGURATIONS
OUT 1 V- 2 +IN 3
AD8628
TOP VIEW (Not to Scale)
5
V+
4
-IN
Figure 1. 5-Lead TSOT (UJ-5) and 5-Lead SOT-23 (RJ-5)
NC 1 -IN 2 +IN 3
8
NC V+
AD8628
7
APPLICATIONS
Automotive sensors Pressure and position sensors Strain gage amplifiers Medical instrumentation Thermocouple amplifiers Precision current sensing Photodiode amplifier
NC = NO CONNECT
Figure 2. 8-Lead SOIC_N (R-8)
OUT A 1 -IN A 2 +IN A 3
8
V+
Figure 3. 8-Lead SOIC_N (R-8) and 8-Lead MSOP (RM-8)
OUT A 1 -IN A 2 +IN A 3 V+ 4
14 OUT D 13 -IN D
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 V, drift of less than 0.005 V/C, and noise of only 0.5 V 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.
AD8630
12 +IN D
TOP VIEW 11 V- (Not to Scale) 10 +IN C +IN B 5 OUT B 7
8
OUT C
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 (-40C to +125C). 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 (c)2002-2008 Analog Devices, Inc. All rights reserved.
02735-066
-IN B 6
9
-IN C
02735-063
OUT B TOP VIEW 6 -IN B (Not to Scale) 5 +IN B V- 4
7
AD8629
02735-002
6 OUT TOP VIEW V- 4 (Not to Scale) 5 NC
02735-001
AD8628/AD8629/AD8630 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications ....................................................................................... 1 General Description ......................................................................... 1 Pin Configurations ........................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Electrical Characteristics--VS = 5.0 V ....................................... 3 Electrical Characteristics--VS = 2.7 V ....................................... 4 Absolute Maximum Ratings............................................................ 5 ESD Caution .................................................................................. 5 Typical Performance Characteristics ............................................. 6 Functional Description .................................................................. 14 1/f Noise ....................................................................................... 14 Peak-to-Peak Noise .................................................................... 15 Noise Behavior with First-Order Low-Pass Filter .................. 15 Total Integrated Input-Referred Noise for First-Order Filter ........................................................................ 15 Input Overvoltage Protection ................................................... 16 Output Phase Reversal ............................................................... 16 Overload Recovery Time .......................................................... 16 Infrared Sensors.......................................................................... 17 Precision Current Shunt Sensor ............................................... 18 Output Amplifier for High Precision DACs ........................... 18 Outline Dimensions ....................................................................... 19 Ordering Guide .......................................................................... 20
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 = 25C, unless otherwise noted. Table 1.
Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current AD8628/AD8629 AD8630 Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Offset Voltage Drift OUTPUT CHARACTERISTICS Output Voltage High Symbol VOS -40C TA +125C IB 30 100 -40C TA +125C IOS -40C TA +125C CMRR AVO VOS/T VOH VCM = 0 V to 5 V -40C TA +125C RL = 10 k, VO = 0.3 V to 4.7 V -40C TA +125C -40C TA +125C RL = 100 k to ground -40C TA +125C RL = 10 k to ground -40C TA +125C RL = 100 k to V+ -40C TA +125C RL = 10 k to V+ -40C TA +125C -40C TA +125C Output Current POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier 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 IO -40C TA +125C PSRR ISY CIN 1.5 8.0 SR GBP en p-p en in 0.1 Hz to 10 Hz 0.1 Hz to 1.0 Hz f = 1 kHz f = 10 Hz RL = 10 k 1.0 0.05 2.5 0.5 0.16 22 5 pF pF V/s ms MHz V p-p V p-p nV/Hz fA/Hz VS = 2.7 V to 5.5 V -40C TA +125C VO = VS/2 -40C TA +125C 0 120 115 125 120 140 130 145 135 0.002 4.996 4.995 4.98 4.97 1 2 10 15 50 40 30 15 50 100 300 1.5 200 250 5 pA pA nA pA pA V dB dB dB dB V/C V V V V mV mV mV mV mA mA mA mA Conditions Min Typ 1 Max 5 10 Unit V V
0.02
4.99 4.99 4.95 4.95
Output Voltage Low
VOL
5 5 20 20
Short-Circuit Limit
ISC
25
115
130 0.85 1.0
1.1 1.2
dB mA mA
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 = 25C, unless otherwise noted. Table 2.
Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current AD8628/AD8629 AD8630 Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Offset Voltage Drift OUTPUT CHARACTERISTICS Output Voltage High Symbol VOS -40C TA +125C IB 30 100 1.0 50 0 115 110 110 105 100 300 1.5 200 250 2.7 pA pA nA pA pA V dB dB dB dB V/C V V V V mV mV mV mV mA mA mA mA Conditions Min Typ 1 Max 5 10 Unit V V
-40C TA +125C IOS -40C TA +125C CMRR AVO VOS/T VOH VCM = 0 V to 2.7 V -40C TA +125C RL = 10 k, VO = 0.3 V to 2.4 V -40C TA +125C -40C TA +125C RL = 100 k to ground -40C TA +125C RL = 10 k to ground -40C TA +125C RL = 100 k to V+ -40C TA +125C RL = 10 k to V+ -40C TA +125C -40C TA +125C Output Current POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier 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 IO -40C TA +125C PSRR ISY CIN VS = 2.7 V to 5.5 V -40C TA +125C VO = VS/2 -40C TA +125C
130 120 140 130 0.002 2.695 2.695 2.68 2.675 1 2 10 15 15 10 10 5
0.02
2.68 2.68 2.67 2.67
Output Voltage Low
VOL
5 5 20 20
Short-Circuit Limit
ISC
10
115
130 0.75 0.9 1.5 8.0
1.0 1.2
dB mA mA pF pF V/s ms MHz V p-p nV/Hz fA/Hz
SR GBP en p-p en in
RL = 10 k
1 0.05 2 0.5 22 5
0.1 Hz to 10 Hz f = 1 kHz f = 10 Hz
Rev. F | Page 4 of 20
AD8628/AD8629/AD8630 ABSOLUTE MAXIMUM RATINGS
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
Table 4. Thermal Characteristics
Ratings 6V GND - 0.3 V to VS + 0.3 V 5.0 V Indefinite -65C to +150C -40C to +125C -65C to +150C 300C 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
JA1 207 230 158 190 105 148
JC 61 146 43 44 43 23
Unit C/W C/W C/W C/W C/W C/W
JA is specified for worst-case conditions, that is, JA 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.
ESD CAUTION
Rev. F | Page 5 of 20
AD8628/AD8629/AD8630 TYPICAL PERFORMANCE CHARACTERISTICS
180 160
NUMBER OF AMPLIFIERS
100 VS = 2.7V TA = 25C
NUMBER OF AMPLIFIERS
90 80 70 60 50 40 30 20 10
02735-003
VS = 5V VCM = 2.5V TA = 25C
140 120 100 80 60 40 20 0 -2.5 -1.5 -0.5 0.5 INPUT OFFSET VOLTAGE (V) 1.5 2.5
-1.5
-0.5 0.5 INPUT OFFSET VOLTAGE (V)
1.5
2.5
Figure 5. Input Offset Voltage Distribution
Figure 8. Input Offset Voltage Distribution
60 VS = 5V 50 +85C
7 6
NUMBER OF AMPLIFIERS
VS = 5V TA = -40C TO +125C
INPUT BIAS CURRENT (pA)
40
5 4 3 2 1
30
20
+25C
10
-40C
02735-004
0
1
2 3 4 5 INPUT COMMON-MODE VOLTAGE (V)
6
0
2
4 6 TCVOS (nV/C)
8
10
Figure 6. AD8628 Input Bias Current vs. Input Common-Mode Voltage
Figure 9. Input Offset Voltage Drift
1500 VS = 5V 1000 150C 125C 500
1k
VS = 5V TA = 25C
100 OUTPUT VOLTAGE (mV)
INPUT BIAS CURRENT (pA)
10 SOURCE SINK 1
0
-500
-1000
0.1
02735-005
0
1
2 3 4 5 INPUT COMMON-MODE VOLTAGE (V)
6
0.001
0.01 0.1 LOAD CURRENT (mA)
1
10
Figure 7. AD8628 Input Bias Current vs. Input Common-Mode Voltage at 5 V
Figure 10. Output Voltage to Supply Rail vs. Load Current
Rev. F | Page 6 of 20
02735-008
-1500
0.01 0.0001
02735-007
0
0
02735-006
0 -2.5
AD8628/AD8629/AD8630
1k VS = 2.7V 100 OUTPUT VOLTAGE (mV)
SUPPLY CURRENT (A)
1000
TA = 25C
800
10 SOURCE SINK 1
600
400
0.1
200
02735-009
0.001
0.01 0.1 LOAD CURRENT (mA)
1
10
0
1
2 3 4 SUPPLY VOLTAGE (V)
5
6
Figure 11. Output Voltage to Supply Rail vs. Load Current
Figure 14. Supply Current vs. Supply Voltage
1500 VS = 5V VCM = 2.5V TA = -40C TO +150C
60 GAIN 40
1150
VS = 2.7V CL = 20pF RL = M = 45 0 45
PHASE SHIFT (Degrees) PHASE SHIFT (Degrees)
02735-014 02735-013
INPUT BIAS CURRENT (pA)
900
OPEN-LOOP GAIN (dB)
20
PHASE 90 135
450
0
180 225
100
02735-010
0 -50
-25
0
25 50 75 100 TEMPERATURE (C)
125
150
175
10k
100k 1M FREQUENCY (Hz)
10M
Figure 12. AD8628 Input Bias Current vs. Temperature
Figure 15. Open-Loop Gain and Phase vs. Frequency
1250
TA = 25C
70 60 5V 50 OPEN-LOOP GAIN (dB) GAIN 40 30 PHASE 20 10 0 -10 -20 0 50 100 TEMPERATURE (C) 150 200
02735-011
1000
SUPPLY CURRENT (A)
VS = 5V CL = 20pF RL = M = 52.1 0 45 90 135 180 225
2.7V 750
500
250
0 -50
-30 10k
100k
1M FREQUENCY (Hz)
10M
Figure 13. Supply Current vs. Temperature
Figure 16. Open-Loop Gain and Phase vs. Frequency
Rev. F | Page 7 of 20
02735-012
0.01 0.0001
0
AD8628/AD8629/AD8630
70 60 50 AV = 100 VS = 2.7V CL = 20pF RL = 2k
OUTPUT IMPEDANCE ()
300 270 240 210 180 150 120 90 60 30 10k 100k 1M FREQUENCY (Hz) 10M
VS = 5V
CLOSED-LOOP GAIN (dB)
40 30 20 10 0 -10 -20
AV = 1 AV = 100
AV = 10
AV = 1
AV = 10
1k
10k
100k 1M FREQUENCY (Hz)
10M
100M
Figure 17. Closed-Loop Gain vs. Frequency
Figure 20. Output Impedance vs. Frequency
70 60 50 VS = 5V CL = 20pF RL = 2k
VOLTAGE (500mV/DIV)
CLOSED-LOOP GAIN (dB)
40 30 20 10 0 -10 -20
AV = 100
AV = 10
0V
VS = 1.35V CL = 300pF RL = AV = 1
AV = 1
10k
100k 1M FREQUENCY (Hz)
10M
02735-016
-30 1k
TIME (4s/DIV)
Figure 18. Closed-Loop Gain vs. Frequency
Figure 21. Large Signal Transient Response
300 270 240
OUTPUT IMPEDANCE () VOLTAGE (1V/DIV)
VS = 2.7V
210 180 150 120 90 60 30 1k 10k
AV = 1 AV = 100
0V
VS = 2.5V CL = 300pF RL = AV = 1
AV = 10
100k 1M FREQUENCY (Hz)
10M
100M
02735-017
0 100
TIME (5s/DIV)
Figure 19. Output Impedance vs. Frequency
Figure 22. Large Signal Transient Response
Rev. F | Page 8 of 20
02735-020
02735-019
02735-018
02735-015
-30 1k
0 100
AD8628/AD8629/AD8630
80 VS = 1.35V CL = 50pF RL = AV = 1
VOLTAGE (50mV/DIV) OVERSHOOT (%)
70 60 50 40 30
VS = 2.5V RL = 2k TA = 25C
0V
OS- 20 10 OS+
02735-021
TIME (4s/DIV)
1
10 100 CAPACITIVE LOAD (pF)
1k
Figure 23. Small Signal Transient Response
Figure 26. Small Signal Overshoot vs. Load Capacitance
VS = 2.5V CL = 50pF RL = AV = 1
VOLTAGE (50mV/DIV)
VIN
VS = 2.5V AV = -50 RL = 10k CL = 0pF CH1 = 50mV/DIV CH2 = 1V/DIV
0V
VOLTAGE (V)
0V
0V
VOUT
02735-022
TIME (4s/DIV)
TIME (2s/DIV)
Figure 24. Small Signal Transient Response
Figure 27. Positive Overvoltage Recovery
100 90 80 70
OVERSHOOT (%)
VS = 1.35V RL = 2k TA = 25C
0V VS = 2.5V AV = -50 RL = 10k CL = 0pF CH1 = 50mV/DIV CH2 = 1V/DIV
60 50 40 30 20 10 1 10 100 CAPACITIVE LOAD (pF) 1k
02735-023
OS-
VOLTAGE (V)
VIN
VOUT
OS+
0V
02735-026
0
TIME (10s/DIV)
Figure 25. Small Signal Overshoot vs. Load Capacitance
Figure 28. Negative Overvoltage Recovery
Rev. F | Page 9 of 20
02735-025
02735-024
0
AD8628/AD8629/AD8630
VS = 2.5V VIN = 1kHz @ 3V p-p CL = 0pF RL = 10k AV = 1
VOLTAGE (1V/DIV)
140 120 100 80
PSRR (dB)
VS = 1.35V
60 40 20 0 -20 -40
0V
+PSRR
-PSRR
02735-027
TIME (200s/DIV)
1k
10k 100k FREQUENCY (Hz)
1M
10M
Figure 29. No Phase Reversal
Figure 32. PSRR vs. Frequency
140 120 100 80
CMRR (dB) PSRR (dB)
140 VS = 2.7V 120 100 80 60 40 20 0 -20 -40
02735-028
VS = 2.5V
60 40 20 0 -20 -40 -60 100 1k 10k 100k FREQUENCY (Hz) 1M 10M
+PSRR -PSRR
1k
10k 100k FREQUENCY (Hz)
1M
10M
Figure 30. CMRR vs. Frequency
Figure 33. PSRR vs. Frequency
140 120 100 80
CMRR (dB)
VS = 5V
3.0 VS = 2.7V RL = 10k TA = 25C AV = 1
2.5
OUTPUT SWING (V p-p)
2.0
60 40 20 0 -20 -40
02735-029
1.5
1.0
0.5
1k
10k 100k FREQUENCY (Hz)
1M
10M
1k
10k FREQUENCY (Hz)
100k
1M
Figure 31. CMRR vs. Frequency
Figure 34. Maximum Output Swing vs. Frequency
Rev. F | Page 10 of 20
02735-032
-60 100
0 100
02735-031
-60 100
02735-030
-60 100
AD8628/AD8629/AD8630
5.5 5.0 4.5
OUTPUT SWING (V p-p)
VOLTAGE NOISE DENSITY (nV/Hz)
VS = 5V RL = 10k TA = 25C AV = 1
120 105 90 75 60 45 30 15
02735-036 02735-038 02735-037
VS = 2.7V NOISE AT 1kHz = 21.3nV
4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 1k 10k FREQUENCY (Hz) 100k 1M
02735-033
0 100
0
0
0.5
1.0 1.5 FREQUENCY (kHz)
2.0
2.5
Figure 35. Maximum Output Swing vs. Frequency
Figure 38. Voltage Noise Density at 2.7 V from 0 Hz to 2.5 kHz
0.60 VS = 2.7V 0.45 0.30 VOLTAGE (V) 0.15 0 -0.15 -0.30 -0.45
02735-034
120 105 90 75 60 45 30 15 0 VS = 2.7V NOISE AT 10kHz = 42.4nV
-0.60
0
1
2
3
4
5 6 TIME (s)
7
8
9
10
VOLTAGE NOISE DENSITY (nV/Hz)
0
5
10 15 FREQUENCY (kHz)
20
25
Figure 36. 0.1 Hz to 10 Hz Noise
Figure 39. Voltage Noise Density at 2.7 V from 0 Hz to 25 kHz
0.60 VS = 5V 0.45 0.30 VOLTAGE (V) 0.15 0 -0.15 -0.30 -0.45
02735-035
120 105 90 75 60 45 30 15 0 VS = 5V NOISE AT 1kHz = 22.1nV
-0.60
0
1
2
3
4
5 6 TIME (s)
7
8
9
10
VOLTAGE NOISE DENSITY (nV/Hz)
0
0.5
1.0 1.5 FREQUENCY (kHz)
2.0
2.5
Figure 37. 0.1 Hz to 10 Hz Noise
Figure 40. Voltage Noise Density at 5 V from 0 Hz to 2.5 kHz
Rev. F | Page 11 of 20
AD8628/AD8629/AD8630
120 105 90 75 60 45 30 15
02735-039
150
OUTPUT SHORT-CIRCUIT CURRENT (mA)
VS = 5V NOISE AT 10kHz = 36.4nV
VS = 2.7V TA = -40C TO +150C 100
VOLTAGE NOISE DENSITY (nV/Hz)
50 ISC- 0 ISC+ -50
0
5
10 15 FREQUENCY (kHz)
20
25
-25
0
25 50 75 100 TEMPERATURE (C)
125
150
175
Figure 41. Voltage Noise Density at 5 V from 0 Hz to 25 kHz
Figure 44. Output Short-Circuit Current vs. Temperature
120 105 90 75 60 45 30 15
02735-040
150 OUTPUT SHORT-CIRCUIT CURRENT (mA) VS = 5V VS = 5V TA = -40C TO +150C 100 ISC- 50
VOLTAGE NOISE DENSITY (nV/Hz)
0
-50 ISC+ -25 0 25 50 75 100 TEMPERATURE (C) 125 150 175
02735-043 02735-044
0
0
5 FREQUENCY (kHz)
10
-100 -50
Figure 42. Voltage Noise Density
Figure 45. Output Short-Circuit Current vs. Temperature
150 140
1k VS = 5V OUTPUT-TO-RAIL VOLTAGE (mV) VCC - VOH @ 1k 100 VOL - VEE @ 1k VCC - VOH @ 10k 10 VCC - VOH @ 100k 1 VOL - VEE @ 100k VOL - VEE @ 10k
POWER SUPPLY REJECTION (dB)
130 120 110 100 90 80 70 60 -25 0 25 50 TEMPERATURE (C) 75 100 125
02735-041
VS = 2.7V TO 5V TA = -40C TO +125C
50 -50
0.1 -50
-25
0
25 50 75 100 TEMPERATURE (C)
125
150
175
Figure 43. Power Supply Rejection vs. Temperature
Figure 46. Output-to-Rail Voltage vs. Temperature
Rev. F | Page 12 of 20
02735-042
0
-100 -50
AD8628/AD8629/AD8630
1k VS = 2.7V
140 VS = 2.5V
VCC - VOH @ 1k
OUTPUT-TO-RAIL VOLTAGE (mV)
120
CHANNEL SEPARATION (dB)
100 VOL - VEE @ 1k VCC - VOH @ 10k VOL - VEE @ 10k VCC - VOH @ 100k 1 VOL - VEE @ 100k
100 80 60 40 20 + - R1 10k V- VOUT
10
+2.5V V+ VIN 28mV p-p
R2 100
A
V- -2.5V
B
V+
02735-045
-25
0
25 50 75 100 TEMPERATURE (C)
125
150
175
10k
100k FREQUENCY (Hz)
1M
10M
Figure 47. Output-to-Rail Voltage vs. Temperature
Figure 48. AD8629/AD8630 Channel Separation
Rev. F | Page 13 of 20
02735-062
0.1 -50
0 1k
AD8628/AD8629/AD8630 FUNCTIONAL DESCRIPTION
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 V 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 -40C to +125C, making these amplifiers ideal for a variety of sensitive measurement applications in harsh operating environments. 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%. 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
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 V 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 V 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.
120 105 90 75 60 45 30 15 0 AD8628 (19.4nV/Hz) 0 2 LMC2001 (31.1nV/Hz) LTC2050 (89.7nV/Hz)
VOLTAGE NOISE DENSITY (nV/Hz)
MK AT 1kHz FOR ALL 3 GRAPHS 4 6 FREQUENCY (kHz) 8 10 12
02735-046
Figure 49. Noise Spectral Density of AD8628 vs. Competition
Rev. F | Page 14 of 20
AD8628/AD8629/AD8630
PEAK-TO-PEAK NOISE
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.
en p-p = 0.5V BW = 0.1Hz TO 10Hz
50 45 40 35
NOISE (dB)
30 25 20 15
VOLTAGE (0.5V/DIV)
10 5 0 10 20 30 40 50 60 70 FREQUENCY (kHz) 80 90 100
02735-050 02735-052 02735-051
0
Figure 53. Simulation Transfer Function of the Test Circuit
50
02735-047
45 40 35
TIME (1s/DIV)
Figure 50. AD8628 Peak-to-Peak Noise
NOISE (dB)
30 25 20 15 10 5 0 0 10 20 30 40 50 60 70 FREQUENCY (kHz) 80 90 100
en p-p = 2.3V BW = 0.1Hz TO 10Hz
VOLTAGE (0.5V/DIV)
Figure 54. Actual Transfer Function of the Test Circuit
TIME (1s/DIV)
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.
Figure 51. LTC2050 Peak-to-Peak Noise
NOISE BEHAVIOR WITH FIRST-ORDER LOW-PASS FILTER
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 100k 470pF
TOTAL INTEGRATED INPUT-REFERRED NOISE FOR FIRST-ORDER FILTER
For a first-order filter, the total integrated noise from the AD8628 is lower than the LTC2050.
10
LTC2050
RMS NOISE (V)
AD8551 1
AD8628
02735-049
1k
Figure 52. Test Circuit: First-Order Low-Pass Filter, x101 Gain and 3 kHz Corner Frequency
0.1 10
100 1k 3dB FILTER BANDWIDTH (Hz)
10k
Figure 55. 3 dB Filter Bandwidth in Hz
Rev. F | Page 15 of 20
AD8628/AD8629/AD8630
INPUT OVERVOLTAGE PROTECTION
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. 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.
VIN CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
VOLTAGE (V)
0V
0V
VOUT TIME (500s/DIV)
02735-053
Figure 56. Positive Input Overload Recovery for the AD8628
VIN
CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
OUTPUT PHASE REVERSAL
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. 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.
VOLTAGE (V)
0V
0V
VOUT TIME (500s/DIV)
02735-054
Figure 57. Positive Input Overload Recovery for LTC2050
VIN
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 s, 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.
VOLTAGE (V)
0V
CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
0V
VOUT TIME (500s/DIV)
02735-055
Figure 58. Positive Input Overload Recovery for LMC2001
Rev. F | Page 16 of 20
AD8628/AD8629/AD8630
0V CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
The results shown in Figure 56 to Figure 61 are summarized in Table 5. Table 5. Overload Recovery Time
Product AD8628 LTC2050 LMC2001 Positive Overload Recovery (s) 6 650 40,000 Negative Overload Recovery (s) 9 25,000 35,000
VOLTAGE (V)
VIN
VOUT
0V
02735-056
INFRARED SENSORS
TIME (500s/DIV)
Figure 59. Negative Input Overload Recovery for the AD8628
0V
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. Figure 62 shows a circuit that can amplify ac signals from 100 V to 300 V up to the 1 V to 3 V levels, with gain of 10,000 for accurate analog-to-digital conversion.
10k 100 100k 5V 5V 100V - 300V 10F 100k
VIN VOUT
VOLTAGE (V)
CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
0V
TIME (500s/DIV)
Figure 60. Negative Input Overload Recovery for LTC2050
02735-057
0V CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
VOLTAGE (V)
IR DETECTOR
1/2 AD8629
1/2 AD8629
10k fC 1.6Hz TO BIAS VOLTAGE
02735-059
VIN VOUT
Figure 62. AD8629 Used as Preamplifier for Thermopile
0V
02735-058
TIME (500s/DIV)
Figure 61. Negative Input Overload Recovery for LMC2001
Rev. F | Page 17 of 20
AD8628/AD8629/AD8630
PRECISION CURRENT SHUNT SENSOR
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.
SUPPLY 100k e = 1000 RS I 100mV/mA C 5V 100 I RS 0.1 RL
OUTPUT AMPLIFIER FOR HIGH PRECISION DACS
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 V 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 k). 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 s, add another time constant to the system, increasing the settling time of the output. The settling time of the AD5541 is 1 s. The combined settling time is approximately 1.4 s, as can be derived from the following equation:
t S (TOTAL ) =
AD8628
100k C 100
02735-060
Figure 63. Low-Side Current Sensing
(t S
DAC )2 + (t S AD8628 )2
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 . 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 V 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 0.1F
2.5V
10F
0.1F
SERIAL INTERFACE
VDD CS DIN SCLK LDAC*
REF(REF*)
REFS*
AD8628
AD5541/AD5542
DGND AGND OUT
UNIPOLAR OUTPUT
*AD5542 ONLY
Figure 64. AD8628 Used as an Output Amplifier
Rev. F | Page 18 of 20
02735-061
AD8628/AD8629/AD8630 OUTLINE DIMENSIONS
2.90 BSC
5.00 (0.1968) 4.80 (0.1890)
5
4
1.60 BSC
1 2 3
2.80 BSC
4.00 (0.1574) 3.80 (0.1497)
8 1
5 4
6.20 (0.2441) 5.80 (0.2284)
PIN 1 0.95 BSC *0.90 0.87 0.84 1.90 BSC
0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE
1.27 (0.0500) BSC
1.75 (0.0688) 1.35 (0.0532)
0.50 (0.0196) 0.25 (0.0099) 8 0 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157)
45
0.51 (0.0201) 0.31 (0.0122)
*1.00 MAX
0.20 0.08 8 4 0 0.60 0.45 0.30
0.50 0.30
SEATING PLANE
*COMPLIANT TO JEDEC STANDARDS MO-193-AB WITH THE EXCEPTION OF PACKAGE HEIGHT AND THICKNESS.
Figure 65. 5-Lead Thin Small Outline Transistor Package [TSOT] (UJ-5) Dimensions shown in millimeters
Figure 67. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
3.20 3.00 2.80
2.90 BSC
5
4
1.60 BSC
1 2 3
2.80 BSC
3.20 3.00 2.80 PIN 1
8
5
1
5.15 4.90 4.65
PIN 1 0.95 BSC 1.30 1.15 0.90 1.90 BSC
0.95 0.85 0.75
4
0.65 BSC 1.10 MAX 8 0 0.80 0.60 0.40
1.45 MAX
0.22 0.08 10 5 0 0.60 0.45 0.30
0.15 MAX
0.15 0.00
0.38 0.22 SEATING PLANE
0.50 0.30
0.23 0.08
SEATING PLANE
COPLANARITY 0.10
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
012407-A
0.10 MAX
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.
AD8628/AD8629/AD8630
8.75 (0.3445) 8.55 (0.3366)
14 1 8 7
5.10 5.00 4.90
4.00 (0.1575) 3.80 (0.1496)
6.20 (0.2441) 5.80 (0.2283)
14
8
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10 0.51 (0.0201) 0.31 (0.0122)
1.75 (0.0689) 1.35 (0.0531) SEATING PLANE
0.50 (0.0197) 0.25 (0.0098) 8 0 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157)
4.50 4.40 4.30
45
1 7
6.40 BSC
PIN 1 1.05 1.00 0.80
060606-A
0.65 BSC 1.20 MAX 0.15 0.05 0.30 0.19
0.20 0.09
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.
SEATING COPLANARITY PLANE 0.10
8 0
0.75 0.60 0.45
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 -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C
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
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
Z = RoHS Compliant Part.
(c)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

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