ANALOG DEVICES AD8642 Service Manual
Low Power, Rail-to-Rail Output, Precision
A
A
Data Sheet
FEATURES
Low supply current: 250 μA max
Very low input bias current: 1 pA max
Low offset voltage: 750 μV max
Single-supply operation: 5 V to 26 V
Dual-supply operation: ±2.5 V to ±13 V
Rail-to-rail output
Unity-gain stable
No phase reversal
SC70 package
APPLICATIONS
Line-/battery-powered instruments
Photodiode amplifiers
Precision current sensing
Medical instrumentation
Industrial controls
Precision filters
Portable audio
AT E
GENERAL DESCRIPTION
The AD8641/AD8642/AD8643 are low power, precision JFET
input amplifiers featuring extremely low input bias current and
rail-to-rail output. The ability to swing nearly rail-to-rail at the
input and rail-to-rail at the output enables designers to buffer
CMOS DACs, ASICs, and other wide output swing devices in
single-supply systems. The outputs remain stable with
capacitive loads of more than 500 pF.
The AD8641/AD8642/AD8643 are suitable for applications
utilizing multichannel boards that require low power to manage
heat. Other applications include photodiodes, ATE reference
level drivers, battery management, and industrial controls.
The AD8641/AD8642/AD8643 are fully specified over the
extended industrial temperature range of –40°C to +125°C. The
AD8641 is available in 5-lead SC70 and 8-lead SOIC lead-free
packages. The AD8642 is available in 8-lead MSOP and 8-lead
SOIC lead-free packages. The AD8643 is available in 14-lead
SOIC and 16-lead, 3 mm × 3 mm, LFCSP lead-free packages.
JFET Amplifiers
AD8641/AD8642/AD8643
PIN CONFIGURATIONS
OUT
1
AD8641
VEE
2
TOP VIEW
(Not to Scale)
+IN
3
Figure 1. 5-Lead SC70 (KS-5)
1
NC
AD8641
–IN
2
+IN
3
TOP VIEW
(Not to Scale)
VEE
4
NC = NO CONNECT
Figure 2. 8-Lead SOIC (R-8)
1
OUT
–IN A
+IN A
V–
AD8642
2
3
TOP VIEW
(Not to Scale)
4
Figure 3. 8-Lead SOIC (R-8)
OUT A
1
AD8642
2
–IN A
+IN A
V–
TOP VIEW
3
(Not to Scale)
4
Figure 4. 8-Lead MSOP (RM-8)
1
OUT
2
–IN A
3
+IN A
+IN B
–IN B
OUT B
V+
AD8643
TOP VIEW
4
(Not to Scale)
5
6
7
Figure 5. 14-Lead SOIC (R-14)
NC
161514
1
–IN A
+IN A
V+
+IN B
2
3
4
PIN 1
INDICATOR
AD8643
TOP VIEW
5
OUT A
OUT D
678
NC
13
8
7
6
5
14
13
12
11
10
9
8
5
4
8
7
6
5
8
7
6
5
VCC
–IN
NC
VCC
OUT
NC
V+
OUT B
–IN B
+IN B
V+
OUT B
–IN B
+IN B
OUT D
–IN D
+IN D
V–
+IN C
–IN C
OUT C
12
11
10
9
05072-101
–IN D
+IN D
V–
+IN C
05072-102
05072-105
05072-064
05072-103
–IN B
–IN C
OUT B
OUT C
NOTES
1. NC = NO CONNECT.
2. EXPOSED PAD SHOULD BE CONNECTED TO V+.
05072-104
Figure 6. 16-Lead LFCSP (CP-16) (Not Drawn to Scale)
Rev. E
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rights of third parties that may result from its use. Specifications subject to change without notice. No
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AD8641/AD8642/AD8643 Data Sheet
TABLE OF CONTENTS
Features.............................................................................................. 1
Applications....................................................................................... 1
General Description ......................................................................... 1
Pin Configurations ........................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Electrical Characteristics ............................................................. 3
REVISION HISTORY
9/11—Rev. D to Rev. E
Changes to Thermal Resistance Section........................................ 5
7/11—Rev. C to Rev. D
Changes to Figure 6.......................................................................... 1
11/10—Rev. B to Rev. C
Changes to Figure 6.......................................................................... 1
Added Thermal Resistance Section and Table 4 .......................... 5
Updated Outline Dimensions....................................................... 13
Changes to Ordering Guide.......................................................... 15
4/05—Rev. A to Rev. B
Added AD8643 ...................................................................Universal
Added 14-Lead SOIC.........................................................Universal
Added 16-Lead LFCSP.......................................................Universal
Updated Outline Dimensions....................................................... 13
Changes to Ordering Guide.......................................................... 14
Absolute Maximum Ratings ............................................................5
Thermal Resistance.......................................................................5
ESD Caution...................................................................................5
Typical Performance Characteristics..............................................6
Outline Dimensions....................................................................... 13
Ordering Guide .......................................................................... 15
3/05—Rev. 0 to Rev. A
Added AD8642 ...................................................................Universal
Changes to General Description .....................................................1
Added Figure 3 and Figure 4............................................................1
Changes to Specifications.................................................................3
Changes to Absolute Maximum Ratings........................................5
Changes to Figure 22.........................................................................8
Changes to Figure 23.........................................................................9
Changes to Figure 41...................................................................... 12
Updated Outline Dimensions....................................................... 13
Changes to Ordering Guide.......................................................... 14
10/04—Initial Version: Revision 0
Rev. E | Page 2 of 16
Data Sheet AD8641/AD8642/AD8643
SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
VS = 5.0 V, VCM = 2.5 V, TA = 25°C, unless otherwise noted.
Table 1.
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage VOS 50 750 μV
AD8643 LFCSP only 1 mV
–40°C < TA < +85°C 1.5 mV
+85°C < TA < +125°C, VCM = 1.5 V 1.6 mV
Input Bias Current IB 0.25 1 pA
–40°C < TA < +125°C 180 pA
Input Offset Current IOS 0.5 pA
–40°C < TA < +125°C 60 pA
Input Voltage Range 0 3 V
Common-Mode Rejection Ratio CMRR VCM = 0 V to 2.5 V 74 93 dB
Large Signal Voltage Gain AVO R
Offset Voltage Drift ∆VOS/∆T –40°C < TA < +125°C 2.5 μV/°C
OUTPUT CHARACTERISTICS
Output Voltage High VOH 4.95 V
I
Output Voltage Low VOL 0.05 V
I
Output Current I
±6 mA
OUT
POWER SUPPLY
Power Supply Rejection Ratio PSRR VS = 5 V to 26 V 90 107 dB
Supply Current/Amplifier ISY 195 250 μA
–40°C < TA < +125°C 270 μA
DYNAMIC PERFORMANCE
Slew Rate SR 2 V/μs
Gain Bandwidth Product GBP AD8641, AD8642 3 MHz
AD8643 2.5 MHz
Phase Margin Ø
m
NOISE PERFORMANCE
Voltage Noise eN p-p f = 0.1 Hz to 10 Hz 4.0 μV p-p
Voltage Noise Density eN f = 1 kHz 28.5 nV/√Hz
Current Noise Density iN f = 1 kHz 0.5 fA/√Hz
= 10 kΩ, VO = 0.5 to 4.5 V 80 140 V/mV
L
= 1 mA, –40°C to +125°C 4.94 V
L
= 1 mA, –40°C to +125°C 0.01 0.05 V
L
50 Degrees
Rev. E | Page 3 of 16
AD8641/AD8642/AD8643 Data Sheet
VS= ±13 V, VCM = 0 V, TA =25°C, unless otherwise noted.
Table 2.
Parameter Symbol Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Offset Voltage VOS 70 750 μV
AD8643 LFCSP only 1 mV
–40° < TA < +125°C 1.5 mV
Input Bias Current IB 0.25 1 pA
–40°C < TA < +125°C 260 pA
Input Offset Current IOS 0.5 pA
–40°C < TA < +125°C 65 pA
Input Voltage Range –13 +10 V
Common-Mode Rejection Ratio CMRR VCM = −13 V to +10 V 90 107 dB
Large Signal Voltage Gain AVO R
Offset Voltage Drift ∆VOS/∆T –40°C < TA < +125°C 2.5 μV/°C
OUTPUT CHARACTERISTICS
Output Voltage High VOH +12.95 V
I
Output Voltage Low VOL –12.95 V
I
Output Current I
±12 mA
OUT
POWER SUPPLY
Power Supply Rejection Ratio PSRR VS = ±2.5 V to ±13 V 90 107 dB
Supply Current/Amplifier ISY 200 290 μA
–40°C < TA < +125°C 330 μA
DYNAMIC PERFORMANCE
Slew Rate SR 3 V/μs
Gain Bandwidth Product GBP 3.5 MHz
Phase Margin
Ø
m
NOISE PERFORMANCE
Voltage Noise eN p-p f = 0.1 Hz to 10 Hz 4.2 μV p-p
Voltage Noise Density eN f = 1 kHz 27.5 nV/√Hz
Current Noise Density iN f = 1 kHz 0.5 fA/√Hz
= 10 kΩ, VO = –11 V to +11 V 215 290 V/mV
L
= 1 mA, –40°C to +125°C +12.94 V
L
= 1 mA, –40°C to +125°C –12.94 V
L
60 Degrees
Rev. E | Page 4 of 16
Data Sheet AD8641/AD8642/AD8643
ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings apply at 25°C, unless otherwise noted.
Table 3.
Parameter Rating
Supply Voltage 27.3 V
Input Voltage VS− to VS+
Differential Input Voltage ±Supply Voltage
Output Short-Circuit Duration Indefinite
Storage Temperature Range
KS-5, R-8, RM-8, R-14, CP-16 Packages −65°C to +150°C
Operating Temperature Range −40°C to +125°C
Junction Temperature Range
KS-5, R-8, RM-8, R-14, CP-16 Packages −65°C to +150°C
Lead Temperature (Soldering, 60 sec) 300°C
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.
THERMAL RESISTANCE
θJA 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 4-layer board. For the LFCSP
package, solder the exposed pad to a copper plane, which
should be connected to V+.
Table 4.
Package Type θJA θJC Unit
5-Lead SC70 (KS) 430 149 °C/W
8-Lead SOIC (R) 121 43 °C/W
8-Lead MSOP (RM) 142 45 °C/W
14-Lead SOIC (R) 110 36 °C/W
16-Lead LFCSP (CP) 81 16 °C/W
ESD CAUTION
Rev. E | Page 5 of 16
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