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Precision, 20 MHz, CMOS, Rail-to-Rail Input/Output Operational Amplifiers AD8615/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
current noise. The parts use a patented trimming technique that achieves superior precision without laser trimming. The AD8615/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 AD8615/AD8616/AD8618 offer the highest output drive capability of the 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 AD8615/AD8616/AD8618 are specified over the extended industrial (-40C to +125C) temperature range. The AD8615 is available in 5-lead TSOT-23 packages. 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 TSSOP packages.
APPLICATIONS
Barcode scanners Battery-powered instrumentation Multipole filters Sensors ASIC input or output amplifier Audio Photodiode amplification
GENERAL DESCRIPTION
The AD8615/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
PIN CONFIGURATIONS
OUT 1
5
V+
AD8615
V- 2
04648-B-050
+IN 3
TOP VIEW (Not to Scale)
4
-IN
7
8
Figure 4. 14-Lead TSSOP (RU-14)
OUT A 1
14 OUT D 13 -IN D 12 +IN D
Figure 1. 5-Lead TSOT-23 (UJ-5)
OUT A 1 -IN A 2 +IN A 3
8
V+ OUT B -IN B +IN B
04648-0-001
AD8616
7 6 5
-IN A 2
+IN A 3 V+ 4 +IN B 5
TOP VIEW V- 4 (Not to Scale)
AD8618
11 V- 10 +IN C 9 8
-IN B 6 OUT B 7
-IN C OUT C
OUT A 1 -IN A 2 +IN A 3
8
V+ OUT B -IN B +IN B
04648-0-002
AD8616
7 6 5
TOP VIEW V- 4 (Not to Scale)
Figure 5. 14-Lead SOIC (R-14)
Figure 3. 8-Lead SOIC (R-8) Rev. C
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) 2005 Analog Devices, Inc. All rights reserved.
04648-0-049
Figure 2. 8-Lead MSOP (RM-8)
04648-0-048
OUT A -IN A +IN A V+ +IN B -IN B OUT B
1
14
AD8618
OUT D -IN D +IN D V- +IN C -IN C OUT C
AD8615/AD8616/AD8618 TABLE OF CONTENTS
Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 5 Thermal Resistance ...................................................................... 5 ESD Caution.................................................................................. 5 Typical Performance Characteristics ............................................. 6 Applications..................................................................................... 11 Input Overvoltage Protection ................................................... 11 Output Phase Reversal............................................................... 11 Driving Capacitive Loads .......................................................... 11 Overload Recovery Time .......................................................... 12 D/A Conversion ......................................................................... 12 Low Noise Applications............................................................. 12 High Speed Photodiode Preamplifier...................................... 13 Active Filters ............................................................................... 13 Power Dissipation....................................................................... 13 Power Calculations for Varying or Unknown Loads............. 14 Outline Dimensions ....................................................................... 15 Ordering Guide .......................................................................... 17
REVISION HISTORY
6/05--Rev. B to Rev. C Change to Table 1 ......................................................................... 3 Change to Table 2 ......................................................................... 4 Change to Figure 20 ..................................................................... 8 1/05--Rev. A to Rev. B Added AD8615 ...............................................................Universal Changes to Figure 12.................................................................... 8 Deleted Figure 19; Renumbered Subsequent Figures .............. 8 Changes to Figure 20.................................................................... 9 Changes to Figure 29.................................................................. 10 Changes to Figure 31.................................................................. 11 Deleted Figure 34; Renumbered Subsequent Figures ............ 11 Deleted Figure 35; Renumbered Subsequent Figures ............ 35 4/04--Rev. 0 to Rev. A Added AD8618 ...............................................................Universal Updated Outline Dimensions ................................................... 16 1/04--Revision 0: Initial Version
Rev. C | Page 2 of 20
AD8615/AD8616/AD8618 SPECIFICATIONS
VS =5 V, VCM = VS/2, TA = 25C, unless otherwise noted. Table 1.
Parameter INPUT CHARACTERISTICS Offset Voltage AD8616/AD8618/ AD8615 Symbol VOS Conditions VS = 3.5 V at VCM = 0.5 V and 3.0 V VCM = 0 V to 5 V -40C < TA < +125C -40C < TA < +125C Min Typ 23 23 80 1.5 3 0.2 Max 60 100 500 800 7 10 1 50 550 0.5 50 250 5 Unit V V V V V/C 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 AD8616/AD8618/ AD8615 Input Bias Current
VOS/T IB
-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 2.5 6.7 4.99 4.92 7.5 70 150 3 70 90 1.7 0.1
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
15 100 200
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 Om en p-p en in Cs
12 <0.5 24 63 2.4 10 7 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. C | Page 3 of 20
AD8615/AD8616/AD8618
VS = 2.7 V, VCM = VS/2, TA = 25C, unless otherwise noted. Table 2.
Parameter INPUT CHARACTERISTICS Offset Voltage AD8616/AD8618/ AD8615 Symbol VOS Conditions VS = 3.5 V at VCM = 0.5 V and 3.0 V VCM = 0 V to 2.7 V -40C < TA < +125C -40C < TA < +125C Min Typ 23 23 80 1.5 3 0.2 Max 65 100 500 800 7 10 1 50 550 0.5 50 250 2.7 Unit V V V V V/C 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 AD8616/AD8618/ AD8615 Input Bias Current
VOS/T IB
-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 80 55 100 150 2.5 7.8 2.68 11 50 3 70 90 1.7 0.1
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
25 30
2 2.5
SR ts GBP Om en p-p en in Cs
12 < 0.3 23 42 2.1 10 7 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. C | Page 4 of 20
AD8615/AD8616/AD8618 ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Supply Voltage Input Voltage Differential Input Voltage Output 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, that is, JA is specified for device soldered in circuit board for surface-mount packages. Table 4.
Package Type 5-Lead TSOT-23 (UJ) 8-Lead MSOP (RM) 8-Lead SOIC (R) 14-Lead SOIC (R) 14-Lead TSSOP (RU) JA 207 210 158 120 180 JC 61 45 43 36 35 Unit C/W 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 and 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. C | Page 5 of 20
AD8615/AD8616/AD8618 TYPICAL PERFORMANCE CHARACTERISTICS
2200 2000 1800
NUMBER OF AMPLIFIERS
350
VS = 5V TA = 25C VCM = 0V TO 5V
INPUT BIAS CURRENT (pA)
VS = 2.5V 300 250 200
1600 1400 1200 1000 800 600 400 200
04648-0-003
150 100
50
-700
-500
-300
-100
100
300
500
700
0
25
50
75
100
125
OFFSET VOLTAGE (V)
TEMPERATURE (C)
Figure 6. Input Offset Voltage Distribution
Figure 9. Input Bias Current vs. Temperature
22 20 18 VS = 2.5V TA = -40C TO +125C VCM = 0V
1000 VS = 5V TA = 25C 100
VSY-VOUT (mV)
NUMBER OF AMPLIFIERS
16 14 12 10 8 6 4 2 0 2 4 6 TCVOS (V/C) 8 10 12
04648-0-004
10 SINK
SOURCE 1
0
0.1 0.001
0.01
0.1 1 ILOAD (mA)
10
100
Figure 7. Offset Voltage Drift Distribution
Figure 10. Output Voltage to Supply Rail vs. Load Current
500 400
INPUT OFFSET VOLTAGE (V)
120
VS = 5V TA = 25C
VS = 5V 100 10mA LOAD
OUTPUT VOLTAGE (mV)
300 200 100 0 -100 -200 -300
80
60
40
20
-400
04648-0-005
1mA LOAD
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
0 -40
-25
-10
5
20
35
50
65
80
95
110
125
COMMON-MODE VOLTAGE (V)
TEMPERATURE (C)
Figure 8. Input Offset Voltage vs. Common-Mode Voltage (200 Units, Five Wafer Lots Including Process Skews)
Rev. C | Page 6 of 20
Figure 11. Output Saturation Voltage vs. Temperature
04648-0-008
-500
04648-B-007
04648-0-006
0
0
AD8615/AD8616/AD8618
100 80 60 40 VS = 2.5V TA = 25C Om = 63 225 180 135
120 VS = 2.5V 100
PHASE (Degrees)
90 45 0 -45 -90 -135
80
CMRR (dB)
GAIN (dB)
20 0 -20 -40 -60 -80
60
40
20
04648-B-009
-180 10M FREQUENCY (Hz) -225 60M
-100 1M
1k
10k
100k FREQUENCY (Hz)
1M
10M
Figure 12. Open-Loop Gain and Phase vs. Frequency
Figure 15. Common-Mode Rejection Ratio vs. Frequency
5.0 4.5 4.0
OUTPUT SWING (V p-p)
120
3.5 3.0 2.5 2.0 1.5 1.0 0.5
VS = 5.0V VIN = 4.9V p-p TA = 25C RL = 2k AV = 1
VS = 2.5V 100
80
PSRR (dB)
60
40
20
04648-0-010
1k
10k
100k FREQUENCY (Hz)
1M
10M
1k
10k
100k FREQUENCY (Hz)
1M
10M
Figure 13. Closed-Loop Output Voltage Swing
Figure 16. PSRR vs. Frequency
100 90 80
OUTPUT IMPEDANCE ()
50
VS = 2.5V
SMALL-SIGNAL OVERSHOOT (%)
45 40 35 30 25 20 15 10 5
04648-0-011
VS = 5V RL = TA = 25C AV = 1
70 60 50 40 30 20 10 0 1k AV = 100 AV = 10 AV = 1
-OS +OS
10k
100k
1M
10M
100M
10
100 CAPACITANCE (pF)
1000
FREQUENCY (Hz)
Figure 14. Output Impedance vs. Frequency
Figure 17. Small-Signal Overshoot vs. Load Capacitance
Rev. C | Page 7 of 20
04648-0-014
0
04648-0-013
0
0
04648-0-012
0
AD8615/AD8616/AD8618
2.4
SUPPLY CURRENT PER AMPLIFIER (mA)
2.2 2.0 VS = 5V
VOLTAGE (50mV/DIV)
1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2
VS = 2.7V
VS = 5V RL = 10k CL = 200pF AV = 1
04648-0-015
-25
-10
5
20
35
50
65
80
95
110
125
TEMPERATURE (C)
TIME (1s/DIV)
Figure 18. Supply Current vs. Temperature
Figure 21. Small-Signal Transient Response
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
VOLTAGE (500mV/DIV)
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 19. Supply Current vs. Supply Voltage
Figure 22. Large-Signal Transient Response
1k
0.1 VS = 2.5V VS = 1.35V VS = 2.5V VIN = 0.5V rms AV = 1 BW = 22kHz RL = 100k 0.01
THD+N (%)
VOLTAGE NOISE DENSITY (nV/ Hz 0.5)
100
0.001 10
04648-B-017
1 10 100 1k FREQUENCY (Hz) 10k
100k
20
100
1k FREQUENCY (Hz)
20k
Figure 20. Voltage Noise Density vs. Frequency
Figure 23. THD + N
Rev. C | Page 8 of 20
04648-0-021
0.0001
04648-0-020
0
04648-0-019
0 -40
AD8615/AD8616/AD8618
500
VS = 2.5V VIN = 2V p-p AV = 10
400
VS = 2.7V TA = 25C
INPUT OFFSET VOLTAGE (V)
04648-0-022
300 200 100 0
-100 -200 -300 -400
04648-0-025
VOLTAGE (2V/DIV)
-500
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)
500
VS = 2.7V
400
VS = 3.5V TA = 25C
INPUT OFFSET VOLTAGE (V)
04648-0-023
300 200 100 0
-100 -200 -300 -400
04648-0-026
VOLTAGE (1V/DIV)
-500
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)
1400 VS = 2.7V TA = 25C VCM = 0V TO 2.7V
1000 VS = 1.35V TA = 25C 100
1200
NUMBER OF AMPLIFIERS
1000
800
VSY-VOUT (mV)
10 SOURCE SINK 1
600
400 200
0.1 0.001
04648-0-024
0 -700 -500 -300 -100 100 300 500 700 OFFSET VOLTAGE (V)
0.01
0.1 ILOAD (mA)
1
10
Figure 26. Input Offset Voltage Distribution
Figure 29. Output Voltage to Supply Rail vs. Load Current
Rev. C | Page 9 of 20
04648-B-027
AD8615/AD8616/AD8618
18 VS = 2.7V 16
SMALL SIGNAL OVERSHOOT (%)
50 45 VS = 1.35V RL = TA = 25C AV = 1
VOH @ 1mA LOAD 14
OUTPUT VOLTAGE (mV)
40 35 30 25
12 10 VOL @ 1mA LOAD 8 6 4 2
04648-0-028
-OS 20 15 10 5
+OS
-25
-10
5
20
35
50
65
80
95
110
125
10
100 CAPACITANCE (pF)
1000
TEMPERATURE (C)
Figure 30. Output Saturation Voltage vs. Temperature
Figure 33. Small-Signal Overshoot vs. Load Capacitance
100 80 60 40
GAIN (dB)
225 VS = 1.35V TA = 25C Om = 42 180 135
PHASE (Degrees)
VS = 2.7V RL = 10k CL = 200pF AV = 1
90 45 0 -45 -90 -135
20 0 -20 -40 -60 -80
04648-B-029
-180 10M FREQUENCY (Hz) -225 60M
VOLTAGE (50mV/DIV)
-100 1M
TIME (1s/DIV)
Figure 31. Open-Loop Gain and Phase vs. Frequency
Figure 34. Small-Signal Transient Response
2.7 2.4 2.1 VS = 2.7V VIN = 2.6V p-p TA = 25C RL = 2k AV = 1
VS = 2.7V RL = 10k CL = 200pF AV = 1
OUTPUT SWING (V p-p)
1.8 1.5 1.2 0.9 0.6 0.3
04648-0-030
1k
10k
100k FREQUENCY (Hz)
1M
10M
TIME (1s/DIV)
Figure 32. Closed-Loop Output Voltage Swing vs. Frequency
Figure 35. Large-Signal Transient Response
Rev. C | Page 10 of 20
04648-0-035
0
VOLTAGE (500mV/DIV)
04648-0-034
04648-0-0331
0 -40
0
AD8615/AD8616/AD8618 APPLICATIONS
INPUT OVERVOLTAGE PROTECTION
The AD8615/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. This reduces the overshoot and minimizes ringing, which in turn improves the frequency response of the AD8615/ 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 38 shows the implementation of the snubber, which reduces overshoot by more than 30% and eliminates ringing that 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 AD8615/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.
TIME (2s/DIV)
Phase reversal can cause permanent damage to the amplifier and can create lock-ups in systems with feedback loops.
VS = 2.5V VIN = 6V p-p AV = 1 RL = 10k
VOLTAGE (2V/DIV)
Figure 37. Driving Heavy Capacitive Loads Without Compensation
VCC
+ -
+ -
V- V+ 200 VEE 500pF
04648-0-038
500pF 200mV
VOUT
VIN
Figure 38. Snubber Network
VS = 2.5V AV = 1 RS = 200 CS = 500pF CL = 500pF
04648-0-036
TIME (2ms/DIV)
Figure 36. No Phase Reversal
DRIVING CAPACITIVE LOADS
Although the AD8615/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.
VOLTAGE (100mV/DIV)
TIME (10s/DIV)
Figure 39. Driving Heavy Capacitive Loads Using the Snubber Network
Rev. C | Page 11 of 20
04648-0-039
04648-0-037
AD8615/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 40 and Figure 41 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 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
OUT
AD5542
UNIPOLAR OUTPUT
DGND
AGND
Figure 42. 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 43. 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 10
3 V+ 2 V- 1 R3 100
TIME (1s/DIV)
R2
Figure 40. Positive Overload Recovery
VS = 2.5V RL = 10k AV = 100 VIN = 50mV
-2.5V 0V 0V
1k 3 V+ R4 10 R5 VOUT 1k 3 V+ R7 10 R8 2 V- 100 1 R9 2 V- 1 R6 100
+50mV
1k
04648-0-041
3 V+ R10 10 R11 1k
04648-0-043
TIME (1s/DIV)
1
R12 100
Figure 41. Negative Overload Recovery
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 42 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.
Figure 43. Noise Reduction
Rev. C | Page 12 of 20
04648-0-042
AD8615/AD8616/AD8618
HIGH SPEED PHOTODIODE PREAMPLIFIER
The AD8615/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 and op amp input capacitances. This creates a feedback pole that causes degradation of the phase margin, making the op amp unstable. Therefore, it is 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 46. Second-Order Butterworth, Low-Pass Filter Frequency Response
POWER DISSIPATION
Although the AD8615/AD8616/AD8618 are capable of providing load currents up to 150 mA, the usable output, load current, and drive capability is limited to the maximum power dissipation allowed by the device package.
C2
C1 C2 = 2 R 2 f U where fU is the unity-gain bandwidth of the amplifier.
R2 +2.5V - ID RSH CD CIN + -VBIAS
V- V+
04648-0-044
In any application, the absolute maximum junction temperature for the AD8615/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 47 is a design aid for setting a safe output current drive level or selecting a heat sink for the package options available on the AD8616.
1.5
-2.5V
POWER DISSIPATION (W)
Figure 44. High Speed Photodiode Preamplifier
1.0
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 45 shows the implementation of a second-order, lowpass filter. The Butterworth response has a corner frequency of 100 kHz and a phase shift of 90. The frequency response is shown in Figure 46.
2nF
SOIC
MSOP 0.5
0
20
40
60 80 100 TEMPERATURE (C)
120
140
Figure 47. Maximum Power Dissipation vs. Ambient Temperature
VCC
V- 1.1k VIN 1.1k 1nF VEE V+
04648-0-045
Figure 45. Second-Order, Low-Pass Filter
Rev. C | Page 13 of 20
04648-0-047
0
04648-0-046
-40 0.1
AD8615/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 AD8615/AD8616/AD8618 for any application:
TJ = PDISS x JA + TA
Calculating Power by Measuring Ambient and Case Temperature
The two equations for calculating junction temperature are
TJ = TA + P JA
where:
TJ = junction temperature TA = ambient temperature JA = the junction-to-ambient thermal resistance TJ = TC + P JC
where:
TJ = junction temperature PDISS = power dissipation JA = package thermal resistance, junction-to-case TA = ambient temperature of the circuit
To calculate the power dissipated by the AD8615/ AD8616/AD8618, use
PDISS = ILOAD x (VS - VOUT)
where TC is case temperature and JA and JC are given in the data sheet. The two equations for calculating P (power) are
TA + P JA = TC + P JC P = (TA - TC)/(JC - JA)
where:
ILOAD = output load current VS = supply voltage VOUT = output voltage
Once power has been determined, it is necessary to recalculate the junction temperature to ensure that it has not been exceeded. The temperature should be measured directly on and near the package, but not touching it. Measuring the package can be difficult. A very small bimetallic junction glued to the package can be used, or an infrared sensing device can be used if the spot size is small enough.
The quantity within the parentheses is the maximum voltage developed across either output transistor.
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 is to measure the package temperature and the board temperature. The second is to directly measure the circuits supply current.
Calculating Power by Measuring Supply Current
Power can be calculated directly if the supply voltage and current are known. However, the supply current can have a dc component with a pulse directed into a capacitive load, which could make the rms current very difficult to calculate. This difficulty can be overcome by lifting the supply pin and inserting an rms current meter into the circuit. For this method to work, make sure the current is delivered by the supply pin being measured. This is usually a good method in a singlesupply system; however, if the system uses dual supplies, both supplies may need to be monitored.
Rev. C | Page 14 of 20
AD8615/AD8616/AD8618 OUTLINE DIMENSIONS
3.00 BSC
8.75 (0.3445) 8.55 (0.3366)
5
14 1 8 7
8
3.00 BSC
1
4.90 BSC
4
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
COPLANARITY 0.10 0.25 (0.0098) 0.10 (0.0039)
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 MO-187-AA
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
Figure 48. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters
Figure 50. 14-Lead Standard Small Outline Package [SOIC] Narrow Body (R-14) Dimensions shown in millimeters and (inches)
5.10 5.00 4.90
5.00 (0.1968) 4.80 (0.1890)
8 5
14
4.00 (0.1574) 3.80 (0.1497) 1
6.20 (0.2440)
4.50 4.40 4.30
8
4 5.80 (0.2284)
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-012-AA 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-153-AB-1
Figure 49. 8-Lead Standard Small Outline Package [SOIC] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
Figure 51. 14-Lead Thin Shrink Small Outline Package [TSSOP] (RU-14) Dimensions shown in millimeters
Rev. C | Page 15 of 20
AD8615/AD8616/AD8618
2.90 BSC
5
4
1.60 BSC
1 2 3
2.80 BSC
PIN 1 0.95 BSC *0.90 0.87 0.84 1.90 BSC
*1.00 MAX
0.20 0.08 8 4 0 0.60 0.45 0.30
0.10 MAX
0.50 0.30
SEATING PLANE
*COMPLIANT TO JEDEC STANDARDS MO-193-AB WITH THE EXCEPTION OF PACKAGE HEIGHT AND THICKNESS.
Figure 52. 5-Lead Thin Small Outline Transistor Package [TSOT] (UJ-5) Dimensions shown in millimeters
Rev. C | Page 16 of 20
AD8615/AD8616/AD8618
ORDERING GUIDE
Model AD8615AUJZ-R2 1 AD8615AUJZ-REEL1 AD8615AUJZ-REEL71 AD8616ARM-R2 AD8616ARM-REEL AD8616ARMZ-R21 AD8616ARMZ-REEL1 AD8616AR AD8616AR-REEL AD8616AR-REEL7 AD8616ARZ1 AD8616ARZ-REEL1 AD8616ARZ-REEL71 AD8618AR AD8618AR-REEL AD8618AR-REEL7 AD8618ARZ1 AD8618ARZ-REEL1 AD8618ARZ-REEL71 AD8618ARU AD8618ARU-REEL AD8618ARUZ1 AD8618ARUZ-REEL1
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
Package Description 5-Lead TSOT-23 5-Lead TSOT-23 5-Lead TSOT-23 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 14-Lead SOIC 14-Lead SOIC 14-Lead SOIC 14-Lead SOIC 14-Lead SOIC 14-Lead SOIC 14-Lead TSSOP 14-Lead TSSOP 14-Lead TSSOP 14-Lead TSSOP
Package Option UJ-5 UJ-5 UJ-5 RM-8 RM-8 RM-8 RM-8 R-8 R-8 R-8 R-8 R-8 R-8 R-14 R-14 R-14 R-14 R-14 R-14 RU-14 RU-14 RU-14 RU-14
Branding BKA BKA BKA BLA BLA A0K A0K
Z = Pb-free part.
Rev. C | Page 17 of 20
AD8615/AD8616/AD8618 NOTES
Rev. C | Page 18 of 20
AD8615/AD8616/AD8618 NOTES
Rev. C | Page 19 of 20
AD8615/AD8616/AD8618 NOTES
(c) 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04648-0-6/05(C)
Rev. C | Page 20 of 20

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