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Precision 20 MHz CMOS Rail-to-Rail Input/Output Operational Amplifiers AD8616/AD8618
FEATURES
Low offset voltage: 65 V max Single-supply operation: 2.7 V to 5.5 V Low noise: 8 nV/Hz Wide bandwidth: >20 MHz Slew rate: 12 V/s High output current: 150 mA No phase reversal Low input bias current: 1 pA Low supply current: 2 mA Unity gain stable
PIN CONFIGURATIONS
OUT A 1 -IN A 2 +IN A 3
8
V+ OUT B -IN B +IN B
04648-0-001
AD8616
7 6 5
TOP VIEW V- 4 (Not to Scale)
Figure 1. 8-Lead MSOP (RM-8)
OUT A 1
8
V+
OUT B
04648-0-002
-IN A 2
+IN A 3
AD8616
7
TOP VIEW V- 4 (Not to Scale)
6
-IN B
5
+IN B
APPLICATIONS
Barcode scanners Battery-powered instrumentation Multipole filters Sensors ASIC input or output amplifier Audio Photodiode amplification
Figure 2. 8-Lead SOIC (R-8)
OUT A -IN A +IN A V+ +IN B -IN B OUT B
1 14
AD8618
7 8
Figure 3. 14-Lead TSSOP (RU-14)
OUT A 1
14 OUT D 13 -IN D 12 +IN D
-IN A 2
+IN A 3 V+ 4 +IN B 5 -IN B 6 OUT B 7
AD8618
11 V- 10 +IN C 9 -IN C 8 OUT C
04648-0-049
Figure 4. 14-Lead SOIC (R-14)
GENERAL DESCRIPTION
The AD8616/AD8618 are dual/quad, rail-to-rail, input and output, single-supply amplifiers featuring very low offset voltage, wide signal bandwidth, and low input voltage and current noise. The parts use a patented trimming technique that achieves superior precision without laser trimming. The AD8616/AD8618 are fully specified to operate from 2.7 V to 5 V single supplies. The combination of 20 MHz bandwidth, low offset, low noise, and very low input bias current make these amplifiers useful in a wide variety of applications. Filters, integrators, photodiode amplifiers, and high impedance sensors all benefit from the combination of performance features. AC applications benefit from the wide bandwidth and low distortion. The AD8616/ AD8618 offer the highest output drive capability of the
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.
DigiTrimTM family, which is excellent for audio line drivers and other low impedance applications. Applications for the parts include portable and low powered instrumentation, audio amplification for portable devices, portable phone headsets, bar code scanners, and multipole filters. The ability to swing rail to rail at both the input and output enables designers to buffer CMOS ADCs, DACs, ASICs, and other wide output swing devices in single-supply systems. The AD8616/AD8618 are specified over the extended industrial (-40C to +125C) temperature range. The AD8616 is available in 8-lead MSOP and narrow SOIC surface mount packages; the MSOP version is available in tape and reel only. The AD8618 is available in 14-lead SOIC and 14-lead TSSOP packages.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 (c) 2004 Analog Devices, Inc. All rights reserved.
04648-0-048
OUT D -IN D +IN D V- +IN C -IN C OUT C
AD8616/AD8618 TABLE OF CONTENTS
Specifications..................................................................................... 3 VS = 5 V.......................................................................................... 3 VS = 2.7 V....................................................................................... 4 Absolute Maximum Ratings............................................................ 5 Thermal Resistance ...................................................................... 5 ESD Caution.................................................................................. 5 Typical Performance Characteristics ............................................. 6 Applications..................................................................................... 12 Input Overvoltage Protection ................................................... 12 Output Phase Reversal............................................................... 12 Driving Capacitive Loads.......................................................... 12 Overload Recovery Time .......................................................... 13 D/A Conversion ......................................................................... 13 Low Noise Applications ............................................................. 13 High Speed Photodiode Preamplifier...................................... 14 Active Filters ............................................................................... 14 Power Dissipation ...................................................................... 14 Power Calculations for Varying or Unknown Loads............. 15 Outline Dimensions ....................................................................... 16 Ordering Guide .......................................................................... 16
REVISION HISTORY
4/04--Data Sheet Changed from Rev. 0 to Rev. A Added AD8618................................................................Universal Updated Outline Dimensions ................................................... 16
1/04--Revision 0: Initial Version
Rev. A | Page 2 of 16
AD8616/AD8618 SPECIFICATIONS
VS = 5 V
@VCM = VS/2, TA = 25C, unless otherwise noted. Table 1.
Parameter INPUT CHARACTERISTICS Offset Voltage Symbol VOS Conditions VS = 3.5 V @ VCM = 0.5 V and 3.0 V VCM = 0 V to 5 V -40C < TA < +125C -40C < TA < +125C -40C < TA < +85C -40C < TA < +125C Input Offset Current IOS -40C < TA < +85C -40C < TA < +125C Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Input Capacitance OUTPUT CHARACTERISTICS Output Voltage High CMRR AVO CDIFF CCM VOH VCM = 0 V to 4.5 V RL = 2 k, VO = 0.5 V to 5 V 0 80 105 100 1500 2.6 10 4.99 4.92 7.5 70 150 3 70 90 1.7 15 100 200 0.1 Min Typ 23 80 1.5 0.2 Max 65 500 800 7 1 50 500 0.5 50 250 5 Unit V V V V/C pA pA pA pA pA pA V dB V/mV pF pF V V V mV mV mV mA dB mA mA V/s s MHz Degrees V nV/Hz nV/Hz pA/Hz dB dB
Offset Voltage Drift Input Bias Current
VOS/T IB
Output Voltage Low
VOL
IL = 1 mA IL = 10 mA -40C < TA < +125C IL = 1 mA IL = 10 mA -40C < TA < +125C f = 1 MHz, AV = 1 VS = 2.7 V to 5.5 V VO = 0 V -40C < TA < +125C RL = 2 k To 0.01%
4.98 4.88 4.7
Output Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current per Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Peak-to-Peak Noise Voltage Noise Density Current Noise Density Channel Separation
IOUT ZOUT PSRR ISY
2.0 2.5
SR ts GBP OO en p-p en in Cs
12 <0.5 24 73 2.4 8 6 0.05 -115 -110
0.1 Hz to 10 Hz f = 1 kHz f = 10 kHz f = 1 kHz f = 10 kHz f = 100 kHz
Rev. A | Page 3 of 16
AD8616/AD8618
VS = 2.7 V
@VCM = VS /2, TA = 25C, unless otherwise noted. Table 2.
Parameter INPUT CHARACTERISTICS Offset Voltage Symbol VOS Conditions VS = 3.5 V @ VCM = 0.5 V and 3.0 V VCM = 0 V to 2.7 V -40C < TA < +125C -40C < TA < +125C -40C < TA < +85C -40C < TA < +125C Input Offset Current IOS -40C < TA < +85C -40C < TA < +125C Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Input Capacitance OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Output Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current per Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Peak-to-Peak Noise Voltage Noise Density Current Noise Density Channel Separation CMRR AVO CDIFF CCM VOH VOL IOUT ZOUT PSRR ISY VCM = 0 V to 2.7 V RL = 2 k, VO = 0.5 V to 2.2 V 0 84 55 100 150 2.6 10 2.68 11 50 3 70 90 1.7 25 30 0.1 Min Typ 23 80 1.5 0.2 Max 65 500 800 7 1 50 500 0.5 50 250 2.7 Unit V V V V/C pA pA pA pA pA pA V dB V/mV pF pF V V mV mV mA dB mA mA V/s s MHz Degrees V nV/Hz nV/Hz pA/Hz dB dB
Offset Voltage Drift Input Bias Current
VOS/T IB
IL = 1 mA -40C < TA < +125C IL = 1 mA -40C < TA < +125C f = 1 MHz, AV = 1 VS = 2.7 V to 5.5 V VO = 0 V -40C < TA < +125C RL = 2 k To 0.01%
2.65 2.6
2 2.5
SR ts GBP OO en p-p en in Cs
12 <0.3 22 50 2.1 8 6 0.05 -115 -110
0.1 Hz to 10 Hz f = 1 kHz f = 10 kHz f = 1 kHz f = 10 kHz f = 100 kHz
Rev. A | Page 4 of 16
AD8616/AD8618 ABSOLUTE MAXIMUM RATINGS
Table 3. AD8616/AD8618 Stress Ratings
Parameter Supply Voltage Input Voltage Differential Input Voltage Ouput Short-Circuit Duration to GND Storage Temperature Operating Temperature Range Lead Temperature Range (Soldering 60 sec) Junction Temperature Rating 6V GND to VS 3 V Indefinite -65C to +150C -40C to +125C 300C 150C
THERMAL RESISTANCE
JA is specified for the worst-case conditions, i.e., JA is specified for device soldered in circuit board for surface-mount packages. Table 4.
Package Type 8-Lead MSOP (RM) 8-Lead SOIC (R) 14-Lead SOIC (R) 14-Lead TSSOP (RU) JA 210 158 120 180 JC 45 43 36 35 Unit C/W C/W C/W C/W
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
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. A | Page 5 of 16
AD8616/AD8618 TYPICAL PERFORMANCE CHARACTERISTICS
2200 2000 1800 VS = 5V TA = 25C VCM = 0V TO 5V
350 VS = 2.5V 300
INPUT BIAS CURRENT (pA)
NUMBER OF AMPLIFIERS
1600 1400 1200 1000 800 600 400
250
200
150 100
50
200 -700 -500 -300 -100 100 300 500 700
04648-0-003
0
25
50
75
100
125
OFFSET VOLTAGE (V)
TEMPERATURE (C)
Figure 5. Input Offset Voltage Distribution
Figure 8. Input Bias Current vs. Temperature
22 20 18
NUMBER OF AMPLIFIERS
1000
VS = 2.5V TA = -40C TO +125C VCM = 0V
100
VS = 5V TA = 25C
16
VSY - VOUT (mV)
14 12 10 8 6 4 2
04648-0-004
10
SOURCE
SINK
1
0
2
4
6 TCVOS (V/C)
8
10
12
0.01
0.1
1
10
100
LOAD CURRENT (mA)
Figure 6. Offset Voltage Drift Distribution
Figure 9. Output Voltage to Supply Rail vs. Load Current
500 400 VS = 5V TA = 25C
120 VS = 5V 100 10mA LOAD
OUTPUT VOLTAGE (mV)
INPUT OFFSET VOLTAGE (V)
300 200 100 0 -100 -200 -300
80
60
40
20
-400
04648-0-005
1mA LOAD 0 -40
04648-0-008
-500 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 COMMON-MODE VOLTAGE (V)
-25
-10
5
20
35
50
65
80
95
110
125
TEMPERATURE (C)
Figure 7. Input Offset Voltage vs. Common-Mode Voltage (200 Units, Five Wafer Lots Including Process Skews)
Figure 10. Output Voltage Swing vs. Temperature
Rev. A | Page 6 of 16
04648-0-007
0
0.1 0.001
04648-0-006
0
0
AD8616/AD8618
100 80 60
GAIN (dB)
225 VS = 2.5V TA = 25C 180 M = 74 135
PHASE (Degrees)
120 VS = 2.5V 100
80
CMRR (dB)
40 20 0 -20 -40 1k
90 45 0 -45 -90 100M
60
40
20
10k
100k
1M
10M
04648-0-009
0 1k 10k 100k FREQUENCY (Hz) 1M 10M
FREQUENCY (Hz)
Figure 11. Open-Loop Gain and Phase vs. Frequency
Figure 14. Common-Mode Rejection Ratio vs. Frequency
5.0 4.5 4.0 VS = 5.0V VIN = 4.9V p-p TA = 25C RL = 2k AV = 1
120 VS = 2.5V 100
OUTPUT SWING (V p-p)
3.5 3.0 2.5 2.0 1.5 1.0
80
PSRR (dB)
60
40
20
0.5
04648-0-010
0 1k 10k 100k FREQUENCY (Hz) 1M 10M
1k
10k
100k FREQUENCY (Hz)
1M
10M
Figure 12. Closed-Loop Output Voltage Swing
Figure 15. PSRR vs. Frequency
100 VS = 2.5V 90 80
50 45 VS = 5V RL = TA = 25C AV = 1
SMALL SIGNAL OVERSHOOT (%)
40 35 30 25 20 15 10 5
OUTPUT IMPEDANCE ()
70 60 50 40 30 20 10 0 1k AV = 100 AV = 10 AV = 1
-OS +OS
04648-0-011
10k
100k
1M
10M
100M
10
100 CAPACITANCE (pF)
1000
FREQUENCY (Hz)
Figure 13. Output Impedance vs. Frequency
Figure 16. Small-Signal Overshoot vs. Load Capacitance
Rev. A | Page 7 of 16
04648-0-014
0
04648-0-013
0
D8616-0-012
AD8616/AD8618
2.4
SUPPLY CURRENT PER AMPLIFIER (mA)
56 49 42 35 28 21 14 7
04648-0-015
2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 VS = 2.7V VS = 5V
VOLTAGE NOISE DENSITY (nV/ Hz)
VS = 5V MKR @ 6.70
0 0 1 2 3 4 5 6 FREQUENCY (kHz) 7 8 9 10
TEMPERATURE (C)
Figure 17. Supply Current vs. Temperature
Figure 20. Voltage Noise Density vs. Frequency
2000
SUPPLY CURRENT PER AMPLIFIER (A)
1800 1600 1400 1200 1000 800 600 400 200
04648-0-016
VS = 5V RL = 10k CL = 200pF AV = 1
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
TIME (1s/DIV)
Figure 18. Supply Current vs. Supply Voltage
Figure 21. Small-Signal Transient Response
72 63 54 45 36 27 18 9 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FREQUENCY (kHz) VS = 5V MKR @ 8.72
VOLTAGE NOISE DENSITY (nV/ Hz)
VS = 5V RL = 10k CL = 200pF AV = 1
VOLTAGE (500mV/DIV)
04648-0-017
TIME (1s/DIV)
Figure 19. Voltage Noise Density vs. Frequency
Figure 22. Large-Signal Transient Response
Rev. A | Page 8 of 16
04648-0-020
04648-0-019
0
VOLTAGE (50mV/DIV)
04648-0-018
AD8616/AD8618
0.1 VS = 2.5V VIN = 0.5V rms AV = 1 BW = 22kHz RL = 100k 0.01
1400 VS = 2.7V TA = 25C VCM = 0V TO 2.7V
1200
NUMBER OF AMPLIFIERS
04648-0-021
1000 800
THD+N (%)
600
0.001
400 200
20
100
1k FREQUENCY (Hz)
20k
-700
-500
-300
-100
100
300
500
700
OFFSET VOLTAGE (V)
Figure 23. THD + N
Figure 26. Input Offset Voltage Distribution
500
VS = 2.5V VIN = 2V p-p AV = 10
400
INPUT OFFSET VOLTAGE (V)
VS = 2.7V TA = 25C
300 200 100 0 -100 -200 -300 -400
VOLTAGE (2V/DIV)
04648-0-022
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2.7
TIME (200ns/DIV)
COMMON-MODE VOLTAGE (V)
Figure 24. Settling Time
Figure 27. Input Offset Voltage vs. Common-Mode Voltage (200 Units, Five Wafer Lots Including Process Skews)
VS = 2.7V
500 400 VS = 3.5V TA = 25C
INPUT OFFSET VOLTAGE (V)
300 200 100 0 -100 -200 -300 -400
VOLTAGE (1V/DIV)
04648-0-023
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
TIME (1s/DIV)
COMMON-MODE VOLTAGE (V)
Figure 25. 0.1 Hz to 10 Hz Input Voltage Noise
Figure 28. Input Offset Voltage vs. Common-Mode Voltage (200 Units, Five Wafer Lots Including Process Skews)
Rev. A | Page 9 of 16
04648-0-026
-500
04648-0-025
-500
04648-0-024
0.0001
0
AD8616/AD8618
1000 VS = 2.7V TA = 25C 100 VSY - VOUT (mV)
2.7 2.4 2.1 VS = 2.7V VIN = 2.6V p-p TA = 25C RL = 2k AV = 1
OUTPUT SWING (V p-p)
1.8 1.5 1.2 0.9 0.6 0.3
10
SOURCE
SINK
1
LOAD CURRENT (mA)
04648-0-027
0.01
0.1
1
10
1k
10k
100k FREQUENCY (Hz)
1M
10M
Figure 29. Output Voltage to Supply Rail vs. Load Current
Figure 32. Closed-Loop Output Voltage Swing vs. Frequency
18 VS = 2.7V 16
50 45 VS = 1.35V RL = TA = 25C AV = 1
SMALL SIGNAL OVERSHOOT (%)
VOH @ 1mA LOAD 14
40 35 30 25 20 15 10 5
OUTPUT VOLTAGE (mV)
12 10 VOL @ 1mA LOAD 8 6 4 2
04648-0-028
-OS
+OS
-25
-10
5
20
35
50
65
80
95
110
125
10
100 CAPACITANCE (pF)
1000
TEMPERATURE (C)
Figure 30. Output Voltage Swing vs. Temperature
Figure 33. Small-Signal Overshoot vs. Load Capacitance
100 80 60 40
VOLTAGE NOISE DENSITY (nV/ Hz)
225 VS = 1.35V TA = 25C 180 M = 51 135 90
PHASE (Degrees)
64 56 48 40 32 24 16 8 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 FREQUENCY (kHz) 0.8 0.9 1.0 VS = 2.7V MKR @ 7.47
GAIN (dB)
20 0 -20 -40 -60 -80 -100
45
0
-45 -90 -135 -180
04648-0-029
1k
10k
100k
1M
10M
FREQUENCY (Hz)
Figure 31. Open-Loop Gain and Phase vs. Frequency
Figure 34. Voltage Noise Density vs. Frequency
Rev. A | Page 10 of 16
04648-0-032
-225 100M
04648-0-0331
0 -40
0
04648-0-030
0.1 0.001
0
AD8616/AD8618
48 42 36 30 24 18 12 6 0 0 1 2 3 4 5 6 7 8 9 10 FREQUENCY (kHz)
04648-0-035
VS = 2.7V MKR @ 5.91
VOLTAGE NOISE DENSITY (nV/ Hz)
VS = 2.7V RL = 10k CL = 200pF AV = 1
04648-0-033
VOLTAGE (500mV/DIV)
TIME (1s/DIV)
Figure 35. Voltage Noise Density vs. Frequency
Figure 37. Large-Signal Transient Response
VS = 2.7V RL = 10k CL = 200pF AV = 1
VOLTAGE (50mV/DIV)
TIME (1s/DIV)
Figure 36. Small-Signal Transient Response
Rev. A | Page 11 of 16
04648-0-034
AD8616/AD8618 APPLICATIONS
INPUT OVERVOLTAGE PROTECTION
The AD8616/AD8618 have internal protective circuitry that allows voltages exceeding the supply to be applied at the input. It is recommended, however, not to apply voltages that exceed the supplies by more than 1.5 V at either input of the amplifier. If a higher input voltage is applied, series resistors should be used to limit the current flowing into the inputs. The input current should be limited to <5 mA. The extremely low input bias current allows the use of larger resistors, which allows the user to apply higher voltages at the inputs. The use of these resistors adds thermal noise, which contributes to the overall output voltage noise of the amplifier. For example, a 10 k resistor has less than 13 nV/Hz of thermal noise and less than 10 nV of error voltage at room temperature. AD8616/AD8618. One simple technique for compensation is the snubber, which consists of a simple RC network. With this circuit in place, output swing is maintained and the amplifier is stable at all gains. Figure 40 shows the implementation of the snubber, which reduces overshoot by more than 30% and eliminates ringing, which can cause instability. Using the snubber does not recover the loss of bandwidth incurred from a heavy capacitive load.
VS = 2.5V AV = 1 CL = 500pF
VOLTAGE (100mV/DIV)
OUTPUT PHASE REVERSAL
The AD8616/AD8618 are immune to phase inversion, a phenomenon that occurs when the voltage applied at the input of the amplifier exceeds the maximum input common mode. Phase reversal can cause permanent damage to the amplifier and lock-ups to systems with feedback loops.
VS = 2.5V VIN = 6V p-p AV = 1 RL = 10k
TIME (2s/DIV)
Figure 39. Driving Heavy Capacitive Loads without Compensation
VCC
+ -
VOLTAGE (2V/DIV)
V- V+ 200 VEE 500pF
04648-0-038
VOUT
+
500pF 200mV
VIN
-
Figure 40. Snubber Network
TIME (2ms/DIV)
Figure 38. No Phase Reversal
DRIVING CAPACITIVE LOADS
Although the AD8616/AD8618 are capable of driving capacitive loads of up to 500 pF without oscillating, a large amount of overshoot is present when operating at frequencies above 100 kHz. This is especially true when the amplifier is configured in positive unity gain (worst case). When such large capacitive loads are required, the use of external compensation is highly recommended. This reduces the overshoot and minimizes ringing, which in turn improves the frequency response of the
VOLTAGE (100mV/DIV)
VS = 2.5V AV = 1 RS = 200 CS = 500pF CL = 500pF
04648-0-036
TIME (10s/DIV)
Figure 41. Driving Heavy Capacitive Loads Using the Snubber Network
Rev. A | Page 12 of 16
04648-0-039
04648-0-037
AD8616/AD8618
OVERLOAD RECOVERY TIME
Overload recovery time is the time it takes the output of the amplifier to come out of saturation and recover to its linear region. Overload recovery is particularly important in applications where small signals must be amplified in the presence of large transients. Figure 42 and Figure 43 show the positive and negative overload recovery times of the AD8616. In both cases, the time elapsed before the AD8616 comes out of saturation is less than 1 s. In addition, the symmetry between the positive and negative recovery times allows for excellent signal rectification without distortion to the output signal.
VS = 2.5V RL = 10k AV = 100 VIN = 50mV
0.1F 5V 2.5V 10F + 0.1F
SERIAL INTERFACE
VDD CS DIN SCLK LDAC*
REFF
REFS
1/2 AD8616
VOUT
AD5542
UNIPOLAR OUTPUT
DGND
AGND
Figure 44. Buffering DAC Output
LOW NOISE APPLICATIONS
Although the AD8618 typically has less than 8 nV/Hz of voltage noise density at 1 kHz, it is possible to reduce it further. A simple method is to connect the amplifiers in parallel, as shown in Figure 45. The total noise at the output is divided by the square root of the number of amplifiers. In this case, the total noise is approximately 4 nV/Hz at room temperature. The 100 resistor limits the current and provides an effective output resistance of 50 .
04648-0-040
+2.5V
0V 0V
-50mV
VIN R1
3 V+ 2 V- 1 R3 100
TIME (1s/DIV)
10 R2 1k
Figure 42. Positive Overload Recovery
VS = 2.5V RL = 10k AV = 100 VIN = 50mV
-2.5V 0V 0V
3 V+ R4 10 R5 VOUT 1k 3 V+ R7 10 2 V- 100 R8
04648-0-041
1
R6 100
2
V-
1
R9
+50mV
1k 3 V+ 1 R12 100
04648-0-043
TIME (1s/DIV)
Figure 43. Negative Overload Recovery
R10 10
2
V-
D/A CONVERSION
The AD8616 can be used at the output of high resolution DACs. Their low offset voltage, fast slew rate, and fast settling time make the parts suitable to buffer voltage output or current output DACs. Figure 44 shows an example of the AD8616 at the output of the AD5542. The AD8616's rail-to-rail output and low distortion help maintain the accuracy needed in data acquisition systems and automated test equipment.
R11 1k
Figure 45. Noise Reduction
Rev. A | Page 13 of 16
04648-0-042
AD8616/AD8618
HIGH SPEED PHOTODIODE PREAMPLIFIER
The AD8616/AD8618 are excellent choices for I-to-V conversions. The very low input bias, low current noise, and high unity gain bandwidth of the parts make them suitable, especially for high speed photodiode preamps. In high speed photodiode applications, the diode is operated in a photoconductive mode (reverse biased). This lowers the junction capacitance at the expense of an increase in the amount of dark current that flows out of the diode. The total input capacitance, C1, is the sum of the diode capacitance and that of the op amp. This creates a feedback pole and causes degradation of the phase margin, making the op amp unstable. It is therefore necessary to use a capacitor in the feedback to compensate for this pole. To get the maximum signal bandwidth, select
10
0
GAIN (dB)
-10
-20
-30
1
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
Figure 48. Second-Order Butterworth Low-Pass Filter Frequency Response
POWER DISSIPATION
C2 = C1 2R 2 f U
where fU is the unity gain bandwidth of the amplifier.
C2
R2 +2.5V - ID RSH CD CIN + -VBIAS
V- V+
04648-0-044
Although the AD8616/AD8618 are capable of providing load currents to 150 mA, the usable output load current drive capability is limited to the maximum power dissipation allowed by the device package used. In any application, the absolute maximum junction temperature for the AD8616/AD8618 is 150C; this should never be exceeded because the device could suffer premature failure. Accurately measuring power dissipation of an integrated circuit is not always a straightforward exercise; Figure 49 has been provided as a design aid for setting a safe output current drive level or selecting a heat sink for the package options available on the AD8616.
-2.5V
1.5
Figure 46. High Speed Photodiode Preamplifier
POWER DISSIPATION (W)
ACTIVE FILTERS
The low input bias current and high unity gain bandwidth of the AD8616 make it an excellent choice for precision filter design. Figure 47 shows the implementation of a second-order low-pass filter. The Butterworth response has a corner frequency of 100 kHz and a phase shift of 90. The frequency response is shown in Figure 48.
2nF VCC
1.0
SOIC
MSOP 0.5
0
20
40
60 80 100 TEMPERATURE (C)
120
140
Figure 49. Maximum Power Dissipation vs. Ambient Temperature
V- 1.1k VIN 1.1k 1nF VEE V+
04648-0-045
Figure 47. Second-Order Low-Pass Filter
Rev. A | Page 14 of 16
04648-0-047
0
04648-0-046
-40 0.1
AD8616/AD8618
These thermal resistance curves were determined using the AD8616 thermal resistance data for each package and a maximum junction temperature of 150C. The following formula can be used to calculate the internal junction temperature of the AD8616/AD8618 for any application: TJ = PDISS x JA + TA where: TJ = junction temperature; PDISS = power dissipation; JA = package thermal resistance, junction-to-case; and TA = ambient temperature of the circuit. To calculate the power dissipated by the AD8616/AD8618, use the following equation: PDISS = ILOAD x (VS - VOUT) where: ILOAD = output load current; VS = supply voltage; and VOUT = output voltage. The quantity within the parentheses is the maximum voltage developed across either output transistor.
Calculating Power by Measuring Ambient and Case Temperature
Given the two equations for calculating junction temperature: TJ = TA + P JA where: TJ = junction temperature; TA = ambient temperature. JA = the junction-to-ambient thermal resistance. TJ = TC + P JC where TC is case temperature and JA and JC are given in the data sheet. The two equations can be solved for P (power): TA + P JA = TC + P JC P = (TA - TC)/(JC - JA) Once power has been determined, it is necessary to go back and calculate the junction temperature to assure that it has not been exceeded. The temperature measurements should be directly on the package and on a spot on the board that is near the package but not touching it. Measuring the package could be difficult. A very small bimetallic junction glued to the package could be used; an infrared sensing device could be used if the spot size is small enough.
POWER CALCULATIONS FOR VARYING OR UNKNOWN LOADS
Often, calculating power dissipated by an integrated circuit to determine if the device is being operated in a safe range is not as simple as it might seem. In many cases, power cannot be directly measured. This may be the result of irregular output waveforms or varying loads; indirect methods of measuring power are required. There are two methods to calculate power dissipated by an integrated circuit. The first can be done by measuring the package temperature and the board temperature. The other is to directly measure the circuit's supply current.
Calculating Power by Measuring Supply Current
Power can be calculated directly if the supply voltage and current are known. However, supply current may have a dc component with a pulse into a capacitive load. This could make rms current very difficult to calculate. This can be overcome by lifting the supply pin and inserting an rms current meter into the circuit. For this to work, the user must be sure that all of the current is being delivered by the supply pin being measured. This is usually a good method in a single-supply system; however, if the system uses dual supplies, both supplies may need to be monitored.
Rev. A | Page 15 of 16
AD8616/AD8618 OUTLINE DIMENSIONS
3.00 BSC
14 1
8.75 (0.3445) 8.55 (0.3366)
5
8 7
8
3.00 BSC
4
4.90 BSC
4.00 (0.1575) 3.80 (0.1496)
6.20 (0.2441) 5.80 (0.2283)
PIN 1 0.65 BSC 1.10 MAX 8 0 0.80 0.60 0.40
0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10
1.27 (0.0500) BSC
1.75 (0.0689) 1.35 (0.0531)
0.50 (0.0197) x 45 0.25 (0.0098)
0.15 0.00 0.38 0.22 COPLANARITY 0.10
0.51 (0.0201) 0.31 (0.0122)
SEATING PLANE
8 0.25 (0.0098) 0 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067)
0.23 0.08 SEATING PLANE
COMPLIANT TO JEDEC STANDARDS MS-012AB 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-187AA
Figure 50. 8-Lead Micro Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters
Figure 52. 14-Lead Standard Small Outline Package [SOIC] (R-14) Dimensions shown in millimeters and (inches)
5.00 (0.1968) 4.80 (0.1890)
8 5 4
5.10 5.00 4.90
4.00 (0.1574) 3.80 (0.1497) 1
6.20 (0.2440) 5.80 (0.2284)
4.50 4.40 4.30
14
8
6.40 BSC
1 7
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040)
1.75 (0.0688) 1.35 (0.0532)
0.50 (0.0196) x 45 0.25 (0.0099)
PIN 1 1.05 1.00 0.80
0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE
8 0.25 (0.0098) 0 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067)
0.65 BSC 1.20 MAX 0.15 0.05 0.30 0.19 0.20 0.09 8 0 0.75 0.60 0.45
COMPLIANT TO JEDEC STANDARDS MS-012AA 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
COMPLIANT TO JEDEC STANDARDS MO-153AB-1
Figure 51. 8-Lead Standard Small Outline Package [SOIC] (R-8) Dimensions shown in millimeters and (inches)
Figure 53. 14-Lead Thin Shrink Small Outline Package [TSSOP] (RU-14) Dimensions shown in millimeters
ORDERING GUIDE
Model AD8616ARM-R2 AD8616ARM-REEL AD8616AR AD8616AR-REEL AD8616AR-REEL7 AD8618AR AD8618AR-REEL AD8618AR-REEL7 AD8618ARU AR8618ARU-REEL 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 Package Description 8-Lead MSOP 8-Lead MSOP 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 14-Lead SOIC 14-Lead SOIC 14-Lead SOIC 14-Lead TSSOP 14-Lead TSSOP Package Outline RM-8 RM-8 R-8 R-8 R-8 R-14 R-14 R-14 RU-14 RU-14 Branding Code BLA BLA
(c) 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04648-0-4/04(A)
Rev. A | Page 16 of 16

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