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36 V, 19 MHz, Low Noise, Low Bias Current, JFET Operational Amplifier ADA4627-1
FEATURES
Low offset voltage: 200 V maximum Offset drift: 1 V/C typical Very low input bias current: 5 pA maximum Extended temperature range: -40C to +125C 5 V to 15 V dual-supply Guaranteed GBW: 16 MHz Voltage noise: 6.1 nV/Hz at 1 kHz High slew rate: 60 V/s High gain: 120 dB typical High CMRR: 116 dB typical High PSRR: 112 dB typical Low supply current: 7.5 mA maximum
PIN CONFIGURATIONS
NULL 1 -IN 2 +IN 3 V- 4
8
NC V+ OUT
07559-001
ADA4627-1
TOP VIEW (Not to Scale)
7 6 5
NULL
NC = NO CONNECT
Figure 1. 8-Lead SOIC_N (R-8)
PIN 1 INDICATOR
NC 1 -IN 2 +IN 3 V- 4
8 NC 7 V+ 6 OUT 5 NC
ADA4627-1
TOP VIEW (Not toScale)
APPLICATIONS
High impedance sensors Photo diode amplifier Precision instrumentation Phase-locked loop filters High end, professional audio DAC output amplifier ATE Medical
Figure 2. 8-Lead LFCSP_VD (CP-8-2)
GENERAL DESCRIPTION
The ADA4627-1 is a wide bandwidth precision amplifier featuring low noise, very low offset, drift, and bias current. Operation is specified from 5 V to 15 V dual supply. The ADA4627-1 provides benefits previously found in few amplifiers. This amplifier combines the best specifications of precision dc and high speed ac op amps. With a typical offset voltage of only 70 V, drift of less than 1 V/C, and noise of only 0.86 V p-p (0.1 Hz to 10 Hz), the ADA4627-1 is suited for applications in which error sources cannot be tolerated. The ADA4627-1 is specified for both the industrial temperature range of -25C to +85C and the extended industrial temperature range of -40C to +125C. It is available in tiny 8-lead LFCSP and 8-lead SOIC packages. The ADA4627-1 is a member of a growing series of high speed, precision op amps offered by Analog Devices, Inc (see Table 1). Table 1. High Speed Precision Op Amps
Supply Single Dual Quad 5 V Low Cost AD8615 AD8616 AD8618 5V AD8651 AD8652 26 V Low Power AD8610 AD8620 30 V Low Cost AD8510 AD8512 AD8513 30 V ADA4627-1
Rev. A
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)2009 Analog Devices, Inc. All rights reserved.
07559-002
NOTES 1. NC = NO CONNECT. 2. CONNECT EXPOSED PAD TO GROUND.
ADA4627-1 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications ....................................................................................... 1 Pin Configurations ........................................................................... 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Electrical Characteristics--30 V Operation ............................. 3 Absolute Maximum Ratings............................................................ 5 Thermal Resistance ...................................................................... 5 ESD Caution .................................................................................. 5 Typical Performance Characteristics ............................................. 6 Theory of Operation ...................................................................... 12 Input Voltage Range ................................................................... 12 Input Offset Voltage Adjust Range........................................... 12 Input Bias Current ...................................................................... 12 Noise Considerations ................................................................. 12 THD + N Measurements ........................................................... 12 Printed Circuit Board Layout, Bias Current, and Bypassing ..................................................................................... 13 Output Phase Reversal ............................................................... 13 Driving Capacitive Loads .......................................................... 13 Outline Dimensions ....................................................................... 14 Ordering Guide .......................................................................... 15
REVISION HISTORY
9/09--Rev. 0 to Rev. A Changes to General Description Section ...................................... 1 Changes to Table 2 ............................................................................ 3 Updated Outline Dimensions ....................................................... 14 Changes to Ordering Guide .......................................................... 15 7/09--Revision 0: Initial Version
Rev. A | Page 2 of 16
ADA4627-1 SPECIFICATIONS
ELECTRICAL CHARACTERISTICS--30 V OPERATION
VSY = 15 V, VCM = 0 V, TA = 25C, unless otherwise noted. Table 2.
B Grade Parameter INPUT CHARACTERISTICS Offset Voltage 1 Symbol VOS -40C TA +85C -40C TA +125C -40C TA +125C VSY = 4.5 V to 18 V -40C TA +125C -40C TA +85C -40C TA +125C Input Offset Current IOS -40C TA +85C -40C TA +125C NOISE PERFORMANCE Voltage Noise Density en f = 10 Hz f = 100 Hz f = 1 kHz f = 10 kHz 0.1 Hz to 10 Hz f = 100 Hz 0.1 Hz to 10 Hz 16.5 7.9 6.1 4.8 0.69 1.6 30 10 8 7 -11 -10.5 106 98 112 110 102 40 40 +11 +10.5 116 -11 -10.5 100 97 106 104 100 40 40 0.5 Conditions Min Typ 70 Max 200 350 400 2 103 99 5 0.5 2 5 0.5 2 40 20 8 6 1.6 Min A Grade Typ 120 Max 300 410 660 3 Unit V V V/C dB dB pA nA nA pA nA nA nV/Hz nV/Hz nV/Hz nV/Hz V p-p fA/Hz fA p-p T pF pF +11 +10.5 110 V V dB
Offset Voltage Drift, Average Power Supply Rejection Ratio Input Bias Current 2
VOS/T PSRR IB
106 101
1 112 1
1 108 1
0.5
5 0.5 2 5 0.5 2 40 20 8 6 1.6
Voltage Noise Current Noise Density Current Noise Input Resistance Input Capacitance, Differential Mode Input Capacitance, Common Mode Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain
en p-p in In p-p RIN CINDM CINCM
16.5 7.9 6.1 4.8 0.69 2.5 48 10 8 7
CMRR
AVO
-40C TA +125C -40C TA +125C, VCM = -11 V to +11 V VCM = -10.5 V to +10.5 V RL = 1 k, VO = -10 V to +10 V -40 TA +85C -40 TA +125C 10 V step, RL = 1 k, CL = 100 pF, AV = +1 10 V step, RL = 1 k, CL =100 pF, Rs = Rf = 1 k AV = -1 VIN = 10 V step, CL = 35 pF, RL = 1 k, AV = -1 VIN = 10 V step, CL = 35 pF, RL = 1 k, AV = -1 RL = 1 k, CL = 20 pF, AV = 1 RL = 1 k, CL = 20 pF, AV = 1 f = 1 kHz, AV = 1
120
120
dB dB dB V/s
DYNAMIC PERFORMANCE Slew Rate
SR SR
56/78 3 82/843 550 450
56/783 82/843 550 450
Settling Time to 0.01% Settling Time to 0.1% Gain Bandwidth Product Phase Margin Total Harmonic Distortion + Noise
tS tS GBP M THD + N
ns ns MHz Degrees %
16 4
19 72 0.000045
164
19 72 0.000045
Rev. A | Page 3 of 16
ADA4627-1
B Grade Parameter POWER SUPPLY Supply Current per Amplifier OUTPUT CHARACTERISTICS Output Voltage High Symbol ISY Conditions IO = 0 mA -40C TA +125C RL = 1 k to VCM -40C TA +85C -40C TA +125C RL = 1 k to VCM -40C TA +85C -40C TA +125C VO = 10 V TA = 25C f = 1 MHz, AV = -100 12.0 11.8 11.7 Min Typ 7.0 Max 7.5 7.8 12.0 11.8 11.7 -12.7 Min A Grade Typ 7.0 Max 7.5 7.8 Unit mA mA V V V V V V mA mA
VOH
12.3
12.3
Output Voltage Low
VOL
-12.7
-12.3 -12.1 -12.0
Output Current Short-Circuit Current Closed-Loop Output Impedance
1 2 3 4
Iout ISC ZOUT
45 +70/-55 41
-12.3 -12.1 -12.0 45 +70/-55 41
VOS is measured fully warmed-up.
Tested/extrapolated from 125C
Rising/falling. Not tested. Guaranteed by simulation and characterization.
Rev. A | Page 4 of 16
ADA4627-1 ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Supply Voltage Input Voltage Range 1 Input Current1 Differential Input Voltage2 Output Short-Circuit Duration to GND Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature (Soldering, 60 sec) ESD Human Body Model
1
THERMAL RESISTANCE
Rating 36 V (V-) - 0.3 V to (V+) + 0.3 V 10 mA VSY Indefinite -65C to +150C -40C to +125C -65C to +150C 300C 2.5 kV
JA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. This was measured using a standard two-layer board. For the LFCSP package, the exposed pad should be soldered to a copper plane. Table 4. Thermal Resistance
Package Type 8-Lead SOIC_N (R-8) 8-Lead LFCSP (CP-8-2) JA 155 77 JC 45 14 Unit C/W C/W
ESD CAUTION
Input pin has clamp diodes to the power supply pins. Input current should be limited to 10 mA or less whenever input signals exceed the power supply rail by 0.3 V. 2 Differential input voltage is limited to 30 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.
Rev. A | Page 5 of 16
ADA4627-1 TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25C, unless otherwise noted.
100 120 100 80 60 270 225 180 135 78 90 45 0 ADA4627-1 TA = 25C VSY = 15V 1k 10k 100k 1M FREQUENCY (Hz) 19.1MHz -45 -90 100M
VOLTAGE NOISE DENSITY (nVHz)
10
40 20 0
ADA4627-1 TA = 25C VSY = 15V
07559-003
-20 -40
0.1 1 FREQUENCY (kHz)
10
10M
Figure 3. Voltage Noise Density
140 100
Figure 6. Open-Loop Gain and Phase vs. Frequency
OPEN-LOOP GAIN (dB)
120
RL = 1k
10 AV = -10
100
ZOUT ()
RL = 600
1
AV = -100
80
ADA4627-1 TA = 25C VSY = 15V VO = 11V
07559-004
0.1
AV = -1 ADA4627-1 TA = 25C VSY = 15V
-25
0
25 50 TEMPERATURE (C)
75
100
125
1k
10k
100k 1M FREQUENCY (Hz)
10M
100M
Figure 4. Open-Loop Gain vs. Temperature
120
Figure 7. Closed-Loop ZOUT vs. Frequency
150
100
100
80
50
VOS (V)
CMRR (dB)
60
0
40
-50 ADA4627-1 TA = 25C VSY = 15V
20
07559-010
0 100
1k
10k 100k FREQUENCY (Hz)
1M
10M
-150 -15
-10
5
0 VCM (V)
5
10
15
Figure 5. CMRR vs. Frequency
Figure 8. VOS vs. Common-Mode Voltage
Rev. A | Page 6 of 16
07559-069
ADA4627-1 TA = 25C VSY = 15V
-100
07559-007
60 -50
0.01 100
07559-006
1 0.01
PHASE (Degrees)
GAIN (dB)
ADA4627-1
TA = 25C, unless otherwise noted.
120
COMMON-MODE REJECTION RATIO (dB)
120
100
110
80
PSRR (dB)
100
60 PSRR- 40 ADA4627-1 TA = 25C VSY = 15V
07559-009
90
PSRR+
80 ADA4627-1 VSY = 15V VCM = 11.5V -25 0 25 50 75 100 125
07559-012
20
70
0 100
1k
10k
100k
1M
10M
60 -50
FREQUENCY (Hz)
TEMPERATURE (C)
Figure 9. PSRR vs. Frequency
8 -40C 7 6 5 4 3 2 1 0 0 4 8 12 16 20 24 SUPPLY VOLTAGE (V) 28 32 36
1 0.001
Figure 12. CMRR vs. Temperature
20 ADA4627-1 TA = 25C VSY = 15V
SUPPLY CURRENT (mA)
+25C
+85C
+125C
10
ADA4627-1 TA = 25C
07559-058
07559-011
VOL - VSS (V)
0.01
0.1 1 ILOAD (mA)
10
100
Figure 10. Supply Current vs. Supply Voltage and Temperature
120
20
Figure 13. VOUT Sinking vs. ILOAD Current
ADA4627-1 TA = 25C VSY = 15V 10
PSRR (dB)
110
07559-068
100 -40
-20
0
20 40 60 TEMPERATURE (C)
80
100
120
1 0.001
0.01
0.1 1 ILOAD (mA)
10
100
Figure 11. PSRR vs. Temperature
Figure 14. VOUT Sourcing vs. ILOAD Current
Rev. A | Page 7 of 16
07559-057
ADA4627-1 RL = 1k 4.5V < VSY < 15V
VDD - VOH (V)
ADA4627-1
TA = 25C, unless otherwise noted.
8 7 6
0.01 ADA4627-1 TA = 25C VSY = 15V VIN = 810mV RL = 600 80kHz FILTER
SUPPLY CURRENT (mA)
4 3 2
THD + N (%)
5
0.001
0.0001
ADA4627-1 TA = 25C SOIC PACKAGE
07559-015
0 0 4 8 12 16 20 24 28 32 36 SUPPLY VOLTAGE (V)
0.00001 0.01
0.1
1 FREQUENCY (kHz)
10
Figure 15. Supply Current vs. Supply Voltage
0.1 10,000
Figure 18. THD + N vs. Frequency
ADA4627-1 VSY = 15 1,000 0.01 MEASURED THD + N (%) 100 0.001
IB (pA)
10 0.0001 ADA4627-1 TA = 25C VSY = 15V VIN = 1kHz RL = 600 80kHz FILTER 0.01 0.1 AMPLITUDE (V rms) 1
1
07559-072
EXTRAPOLATED
07559-078
y = 0.2895 0.0647x R2 = 0.9991 0.1 10 30 50 70 90 TEMPERATURE (C) 110
0.00001 0.001
130
Figure 16. THD + N vs. VIN
60 50 40 AV = +100 ADA4627-1 TA = 25C VSY = 15
Figure 19. Input Bias Current vs. Temperature
100 75 50 25
IB (pA)
IB+ +85C IB-
GAIN (dB)
30 20 AV = +10 10 0 AV = +1
07559-070
+25C 0
IB+ IB-
-25 -50
07559-073
-10 -20 10 100 1k 10k 100k FREQUENCY (kHz) 1M 10M
-75 -100 -15
ADA4627-1 VSY = 15V -10 -5 0 VCM (V) 5 10 15
100M
Figure 17. Closed-Loop Gain vs. Frequency
Figure 20. Input Bias Current vs. VCM and Temperature
Rev. A | Page 8 of 16
07559-071
1
ADA4627-1
TA = 25C, unless otherwise noted.
1200 1100 1000 900 800
IB (pA)
700 600 500 400 300 200 100 0 -15 -10 -5 0 VCM (V) 5 ADA4627-1 TA = 125C VSY = 15V
IB-
OUTPUT VOLTAGE (5V/DIV)
IB+
1
07559-074
10
15
TIME (1s/DIV)
Figure 21. Input Bias Current vs. VCM at 125C
80 60 40 20
VOS (V)
Figure 24. Large Signal Transient Response
ADA4627-1 TA = 25C VSY = 15V
OUTPUT VOLTAGE (5V/DIV)
ADA4627-1 TA = 25C AV = +1 VIN = 20V p-p RF = 0
0 -20 -40 -60 -80
1
07559-075
0
60
120 180 TIME (Seconds)
240
300
TIME (200ns/DIV)
Figure 22. Input Offset Voltage vs. Time
60
Figure 25 Large Signal Transient Response
OVERSHOOT (%)
40 OS+
OUTPUT VOLTAGE (5V/DIV)
50
OS-
ADA4627-1 TA = 25C AV = -1 VIN = 20V p-p RF = RIN = 2k
30
1
20
0 1 10 100 1000 LOAD CAPACITANCE (pF)
07559-023
10,000
CH1 5.00V
TIME (200ns/DIV)
Figure 23. Small Signal Overshoot vs. Load Capacitance
Figure 26. Large Signal Transient Response
Rev. A | Page 9 of 16
07559-059
10
TA = 25C VSY = 15V AV = +1 VIN = 100mV p-p
07559-062
07559-061
ADA4627-1 TA = 25C AV = -1 VIN = 20V p-p RF = RIN = 2k CF = 10pF RL = 1k CL = 1nF
ADA4627-1
TA = 25C, unless otherwise noted.
OUTPUT VOLTAGE (50mV/DIV)
OUTPUT VOLTAGE (5V/DIV)
1
1
TIME (1s/DIV)
TIME (200ns/DIV)
Figure 27. Large Signal Transient Response
ADA4627-1 TA = 25C AV = -1 VIN = 20V p-p RF = RIN = 2k CF = 10pF RL = 1k CL = 100pF
1
Figure 30. Small Signal Transient Response
OUTPUT VOLTAGE (50mV/DIV)
OUTPUT VOLTAGE (5V/DIV)
1
07559-060
TIME (200ns/DIV)
TIME (200ns/DIV)
Figure 28. Large Signal Transient Response
Figure 31. Small Signal Transient Response
OUTPUT VOLTAGE (50mV/DIV)
OUTPUT VOLTAGE (50mV/DIV)
1
1
ADA4627-1 TA = 25C AV = +1 VIN = 200mV p-p RF = 0
07559-064
TIME (200ns/DIV)
TIME (200ns/DIV)
Figure 29. Small Signal Transient Response
Figure 32. Small Signal Transient Response
Rev. A | Page 10 of 16
07559-067
ADA4627-1 TA = 25C AV = -1 VIN = 200mV p-p RF = RIN = 2k CF = 5pF RL = 1k CL = 100pF
07559-065
ADA4627-1 TA = 25C AV = +1 VIN = 200mV p-p RF = 0 RL = 1k CL = 1nF
07559-066
07559-063
ADA4627-1 TA = 25C AV = +1 VIN = 20V p-p RF = 0 RL = 1k CL = 1nF
ADA4627-1 TA = 25C AV = -1 VIN = 200mV p-p RF = RIN = 2k CF = 5pF
ADA4627-1
TA = 25C, unless otherwise noted.
20 15 10 ADA4627-1 TA = 25C VSY = 15V
1
5 0 -5 VOUT -10 -15 VIN 0 0.5 1.0 1.5 2.0 TIME (ms) 2.5 3.0 3.5 4.0
07559-033
2
VOUT
VIN
OUTPUT VOLTAGE (1mV/DIV)
07559-040
07559-077
ADA4627-1 TA = 25C VSY = 15
-20
INPUT VOLTAGE (5V/DIV)
AMPLITUDE (V)
TIME (200ns/DIV)
Figure 33. No Phase Reversal
Figure 35. Positive Settling Time to 0.01%
VIN
2
OUTPUT VOLTAGE (200mV/DIV)
1
OUTPUT VOLTAGE (1mV/DIV)
ADA4627-1 TA = 25C VSY = 15
INPUT VOLTAGE (5V/DIV)
VOUT
1
TIME (200ns/DIV)
07559-076
ADA4627-1 TA = 25C VSY = 15V DUT GAIN = 100 4TH ORDER BAND PASS FIXTURE GAIN = 10k TOTAL GAIN = 1M TIME (1s/DIV)
Figure 34. Negative Settling Time to 0.01%
Figure 36. 0.1 Hz to 10 Hz Noise
Rev. A | Page 11 of 16
ADA4627-1 THEORY OF OPERATION
The ADA4627-1 is a high speed, unity gain stable amplifier with excellent dc characteristics. The typical offset voltage of 70 V allows the amplifier to be easily configured for high gains without the risk of excessive output voltage errors. The small temperature drift of 2 V/C ensures a minimum offset voltage error over the entire temperature range of -40C to +125C, making the amplifier ideal for a variety of sensitive measurement applications in harsh operating environments. chain. Signal chain offset can be addressed with an autozero amplifier used to form a composite amplifier, or if the ADA4627-1 is at an inverting amplifier stage, it can be modified easily to create a summing amplifier where a potentiometer can be added (see Figure 38). The LFCSP package does not have offset adjust pins.
RF
INPUT VOLTAGE RANGE
The ADA4627-1 is not a rail-to-rail input amplifier, thus, care is required to ensure that both inputs do not exceed the input voltage range. 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 the input voltage range, the loop opens and 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 may flow through these diodes, causing permanent damage to the device. If inputs are subject to overvoltage, insert appropriate series resistors to limit the diode current to less than 5 mA.
+ VIN -
RIN
2
ADA4627-1
3
6
+VS 499k 0.1F
+ VOUT -
499k 200
100k -VS
07559-052
Figure 38. Alternate Offset Null Circuit for Inverting Stage
INPUT BIAS CURRENT
Because the ADA4627-1 has a JFET input stage, the input bias current, due to the reverse-biased junction, has a leakage current that approximately doubles every 10C. The power dissipation of the part, combined with the thermal resistance of the package, results in the junction temperature increasing 20 to 30 degrees Centigrade above ambient. This parameter is tested with high speed ATE equipment, which does not result in the die temperature reaching equilibrium. This is correlated with bench measurements to match the guaranteed maximum at room temperature in Table 2. The input current can be reduced by keeping the temperature as low as possible and using a light load on the output.
INPUT OFFSET VOLTAGE ADJUST RANGE
The ADA4627-1 SOIC package has offset adjust pins for compatibility with some existing designs. The recommended offset nulling circuit is shown in Figure 37.
+VS
NOISE CONSIDERATIONS
100k
1
7 2
5
ADA4627-1
3 4
6
The JFET input stage offers very low input voltage noise and input current noise. The thermal noise of a 1 k resistor at room temperature is 4 nV/Hz, thus low values of resistance should be used for dc-coupled inverting and noninverting amplifier configurations. In the case of transimpedance amplifiers (TIAs), current noise is more important. The ADA4627-1 is an excellent choice for both of these applications. Analog Devices offers a wide variety of low voltage noise and low current noise op amps in a variety of processes optimized for different supply voltage ranges. Refer to Application Note AN-940 for a complete discussion of noise, calculations, and selection tables for more than three dozen low noise, op amp families.
07559-051
-VS
Figure 37. Standard Offset Null Circuit
With a 100 k potentiometer, the adjustment range is more than 11 mV. However, the VOS temperature drift increases by several V/C for every millivolt of offset adjust. The ADA4627-1 has matching thin film resistors that are laser trimmed at two temperatures to minimize both offset voltage and offset voltage drift. The offset voltage at room temperature is less than 0.5 mV, and the offset voltage drift is only a few V/C or less, therefore, it is not recommended to use the offset adjust pins, especially for offset adjust of a complete signal
THD + N MEASUREMENTS
Total harmonic distortion plus noise (THD + N) is usually measured with an audio analyzer from Audio Precision, Inc. The analyzer consists of a low distortion oscillator that is swept from the starting frequency to the ending frequency. The
Rev. A | Page 12 of 16
ADA4627-1
oscillator is connected to the circuit under test, and the output of the circuit goes back to the analyzer. The analyzer has a tunable notch filter in lock step with the swept oscillator. This removes the fundamental frequency, but allows all of the harmonics and wideband noise to be measured with an integrating voltmeter. However, there is a switchable low-pass filter in series with the notch filter. If the sine wave is at 100 Hz, then the tenth harmonic is still at 1 kHz, thus having a low pass at 80 kHz is not a problem. When the oscillator reaches 20 kHz, the fourth harmonic (80 kHz) is partially attenuated, resulting in a lower reading from the voltmeter. When evaluating THD + N curves from any manufacturer, careful attention should be paid to the test conditions. The difference between an 80 kHz low-pass filter and a 500 kHz filter is shown in Figure 39.
0.01 ADA4627-1 TA = 25C VSY = 15V VIN = 810mV RL = 600
For a noninverting configuration, the trace can be driven from the feedback divider, but the resistors should be chosen to offer a low impedance drive to the trace (see Figure 41).
GUARD
3
+ VS -
2
ADA4627-1
8
6
VOUT + RF
-
Figure 41. Noninverting Amplifier with Guard
The board layout should be compact with traces as short as possible. For second-order board considerations, such as triboelectric effects and piezoelectric effects, as well as a table of insulating material properties, see the AD549 data sheet. In some cases, shielding from air currents, may be helpful. A general rule of thumb, for op amps with gain bandwidth products higher than 1 MHz, bypass capacitors should be very close to the part, within 3 millimeters. Each supply should be bypassed with a 0.01 F ceramic capacitor in parallel with a 1 F bulk decoupling capacitor. The ceramic capacitors should be closer to the op amp. Sockets, which add inductance and capacitance, should not be used.
0.001
THD + N (%)
0.0001
500kHz FILTER
80kHz FILTER
07559-017
0.00001 0.01
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 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 ADA4627-1 amplifier has been carefully designed to prevent any output phase reversal if both inputs are maintained within the specified input voltage range. If one or both inputs exceed the input voltage range but remain within the supply rails, an internal loop opens and the output varies. Therefore, the inputs should always be a minimum of 3 V away from either supply rail.
0.1
1 FREQUENCY (kHz)
10
100
Figure 39. THD + N vs. Frequency
PRINTED CIRCUIT BOARD LAYOUT, BIAS CURRENT, AND BYPASSING
To take advantage of the very low input bias current of the ADA4627-1 at room temperature, leakage paths must be considered. A printed circuit board, with dust and humidity, can have 100 M of resistance over a few tenths of an inch. A one mV differential between the two points results in 10 pA of leakage current, more than the guaranteed maximum. The op amp inputs should be guarded by surrounding the nets with a metal trace maintained at the predicted voltage. In the case of an inverting configuration or transimpedance amplifier, (see Figure 40), the inverting and noninverting nodes can be surrounded by traces held at a quiet analog ground.
CF GUARD RF
2
DRIVING CAPACITIVE LOADS
Adding capacitance to the output of any op amp results in additional phase shift, which reduces stability and leads to overshoot or oscillation. The ADA4627-1 has a high phase margin and low output impedance, so it can drive reasonable values of capacitance. This is a common situation when an amplifier is used to drive the input of switched capacitor ADCs. For other considerations and various circuit solutions, see the Analog Dialogue article titled Ask the Applications Engineer-25, Op Amps Driving Capacitive Loads, available at www.analog.com.
ADA4627-1
IN
3 8
6
+ VOUT -
07559-053
Figure 40. Inverting Amplifier with Guard
Rev. A | Page 13 of 16
07559-054
RI
ADA4627-1 OUTLINE DIMENSIONS
3.25 3.00 SQ 2.75 0.60 MAX 0.60 MAX
5 8
0.50 BSC
PIN 1 INDICATOR
TOP VIEW
2.95 2.75 SQ 2.55
EXPOSED PAD
(BOT TOM VIEW)
1.60 1.45 1.30 PIN 1 INDICATOR
4
1
0.90 MAX 0.85 NOM SEATING PLANE
12 MAX
0.70 MAX 0.65 TYP
0.50 0.40 0.30 0.05 MAX 0.01 NOM
1.89 1.74 1.59
Figure 42. 8-Lead Lead Frame Chip Scale Package [LFCSP_VD] 3 mm x 3 mm Body, Very Thin, Dual Lead (CP-8-2) Dimensions shown in millimeters
5.00 (0.1968) 4.80 (0.1890)
4.00 (0.1574) 3.80 (0.1497)
8 1
5 4
6.20 (0.2441) 5.80 (0.2284)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE
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)
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.
Figure 43. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
Rev. A | Page 14 of 16
012407-A
090308-B
0.30 0.23 0.18
0.20 REF
FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET.
ADA4627-1
ORDERING GUIDE
Model ADA4627-1ACPZ-R2 1 ADA4627-1ACPZ-RL1 ADA4627-1ACPZ-R71 ADA4627-1ARZ1 ADA4627-1ARZ-RL1 ADA4627-1ARZ-R71 ADA4627-1BRZ1 ADA4627-1BRZ-R71 ADA4627-1BRZ-RL1
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
Package Description 8 Lead LFCSP_VD 8 Lead LFCSP_VD 8 Lead LFCSP_VD 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N
Package Option CP-8-2 CP-8-2 CP-8-2 R-8 R-8 R-8 R-8 R-8 R-8
Branding A29 A29 A29
Z = RoHS Compliant Part.
Rev. A | Page 15 of 16
ADA4627-1 NOTES
(c)2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D07559-0-9/09(A)
Rev. A | Page 16 of 16

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