ANALOG DEVICES AD8638 Service Manual

16 V Auto-Zero, Rail-to-Rail Output

FEATURES

Low offset voltage: 9 μV maximum Offset drift: 0.04 μV/°C maximum Rail-to-rail output swing 5 V to 16 V single-supply or ±2.5 V to ±8 V dual-supply

operation High gain: 136 dB typical High CMRR: 133 dB typical High PSRR: 143 dB typical Very low input bias current: 40 pA maximum Low supply current: 1.3 mA maximum AD8639: qualified for automotive applications

APPLICATIONS

Pressure and position sensors Strain gage amplifiers Medical instrumentation Thermocouple amplifiers Automotive sensors Precision references Precision current sensing

GENERAL DESCRIPTION

The AD8638/AD8639 are single and dual wide bandwidth, auto-zero amplifiers featuring rail-to-rail output swing and low noise. These amplifiers have very low offset, drift, and bias current. Operation is fully specified from 5 V to 16 V single supply (±2.5 V to ±8 V dual supply).

The AD8638/AD8639 provide benefits previously found only in expensive zero-drift or chopper-stabilized amplifiers. Using the Analog Devices, Inc., topology, these auto-zero amplifiers combine low cost with high accuracy and low noise. No external capacitors are required. In addition, the AD8638/AD8639 greatly reduce the digital switching noise found in most chopperstabilized amplifiers.

With a typical offset voltage of only 3 μV, drift of 0.01 μV/°C, and noise of 1.2 μV p-p (0.1 Hz to 10 Hz), the AD8638/AD8639 are suited for applications in which error sources cannot be tolerated. Position and pressure sensors, medical equipment, and strain gage amplifiers benefit greatly from nearly zero drift over their operating temperature ranges. Many systems can take advantage of the rail-to-rail output swing provided by the AD8638/AD8639 to maximize signal-to-noise ratio (SNR).

Operational Amplifiers

AD8638/AD8639

PIN CONFIGURATIONS

AD8638

TOP VIEW

V–

(Not to S cale)

+IN

Figure 1. 5-Lead SOT-23 (RJ-5)

AD8638

–IN

+IN

TOP VIEW

(Not to Scale)

V–

NC = NO CONNECT

Figure 2. 8-Lead SOIC_N (R-8)

OUT A

AD8639

–IN A +IN A

V–

TOP VIEW

(Not to Scale)

Figure 3. 8-Lead MSOP (RM-8)

8-Lead SOIC_N (R-8)

PIN 1

1OUT A

INDICATOR

2–IN A

AD8639

3+IN A

TOP VIEW

(Not to S cal e)

4v–

NOTES

1. PIN 4AND THE EXPOSED PAD MUST BE CONNECTEDTO V–.

Figure 4. 8-Lead LFCSP_WD (CP-8-5)

The AD8638/AD8639 are specified for the extended industrial temperature range (−40°C to +125°C). The single AD8638 is available in tiny 5-lead SOT-23 and 8-lead SOIC packages. The dual AD8639 is available in 8-lead MSOP, 8-lead SOIC, and 8-lead LFCSP packages. See the Ordering Guide for automotive grades.

The AD8638/AD8639 are members of a growing series of autozero op amps offered by Analog Devices (see Ta b l e 1 ).

Table 1. Auto-Zero Op Amps

Supply 2.7 V to 5 V 2.7 V to 5 V Low Power 5 V to 16 V

Single AD8628 AD8538 AD8638 Dual AD8629 AD8539 AD8639 Quad AD8630

V+

–IN

V+

OUT

6 5

V+

8 7

OUT B

–IN B +IN B

8V+ 7OUT B 6 –IN B 5 +IN B

06895-001

06895-002

06895-203

06895-204

Rev. F

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.

AD8638/AD8639

Features .............................................................................................. 1

Applications ....................................................................................... 1

General Description ......................................................................... 1

Pin Configurations ........................................................................... 1

Revision History ............................................................................... 2

Specifications ..................................................................................... 3

Electrical Characteristics—5 V Operation................................ 3

Electrical Characteristics—16 V Operation ............................. 4

Absolute Maximum Ratings ............................................................ 5

Thermal Resistance ...................................................................... 5

ESD Caution .................................................................................. 5

Typical Performance Characteristics ............................................. 6

REVISION HISTORY

6/10—Rev. E to Rev. F

Changes to Features Section and General Description Section . 1

Updated Outline Dimensions ....................................................... 16

Changes to Ordering Guide .......................................................... 18

Added Automotive Products Section .......................................... 18

6/09—Rev. D to Rev. E

Changes to Figure 4 .......................................................................... 1

Changes to Endnote 1 and Endnote 2, Table 4 ............................. 5

Changes to Input Voltage Range Section .................................... 14

Updated Outline Dimensions ....................................................... 16

Changes to Ordering Guide .......................................................... 18

12/08—Rev. C to Rev. D

Changes to Endnote 1, Table 4 ........................................................ 5

Changes to Ordering Guide .......................................................... 28

5/08—Rev. B to Rev. C

Added LFCSP_WD Package ............................................. Universal

Inserted Figure 4; Renumbered Sequentially ................................ 1

Changes to Layout ............................................................................ 1

Changes to General Description .................................................... 1

Changes to Offset Voltage Drift for All Packages Except SOT-23

Parameter in Table 2 ......................................................................... 3

Changes to Table 5 ............................................................................ 5

Updated Outline Dimensions ....................................................... 16

Changes to Ordering Guide .......................................................... 17

Theory of Operation ...................................................................... 14

1/f Noise ....................................................................................... 14

Input Voltage Range ................................................................... 14

Output Phase Reversal ............................................................... 14

Overload Recovery Time .......................................................... 14

Infrared Sensors .......................................................................... 15

Precision Current Shunt Sensor ............................................... 15

Output Amplifier for High Precision DACs ........................... 15

Outline Dimensions ....................................................................... 16

Ordering Guide .......................................................................... 18

Automotive Products ................................................................. 18

4/08—Rev. A to Rev. B

Added AD8639 ................................................................... Universal

Added 8-lead MSOP Package ........................................... Universal

Changes to Features .......................................................................... 1

Changes to General Description ..................................................... 1

Changes Table 2 ................................................................................. 3

Changes to Table 3 ............................................................................. 4

Changes to Table 4, Added Endnote 1 and Endnote 2 ................. 5

Changes to Figure 4 through Figure 9 ............................................ 6

Changes to Figure 11, Figure 12, Figure 14, and Figure 15.......... 7

Changes to Figure 16 through Figure 27 ........................................ 8

Changes to Figure 28 through Figure 33 ..................................... 10

Changes to Figure 34 through Figure 39 ..................................... 11

Changes to Figure 41 and Figure 44............................................. 12

Inserted Figure 46, Figure 47, Figure 49, and Figure 50;

Renumbered Sequentially ............................................................. 13

Changes to Figure 51, Figure 52, and Figure 53 ......................... 15

Updated Outline Dimensions ....................................................... 16

Changes to Ordering Guide .......................................................... 17

11/07—Rev. 0 to Rev. A

Change to Large Signal Voltage Gain Specification ...................... 4

11/07—Revision 0: Initial Version

Rev. F | Page 2 of 20

AD8638/AD8639

SPECIFICATIONS

ELECTRICAL CHARACTERISTICS—5 V OPERATION

VSY = 5 V, VCM = VSY/2, TA = 25°C, unless otherwise noted.

Table 2.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage VOS 3 9 μV

−40°C ≤ TA ≤ +125°C 23 μV

−0.1 V ≤ VCM ≤ +3.0 V 3 9 μV

−40°C ≤ TA ≤ +125°C 23 μV

Input Bias Current IB 1.5 40 pA

−40°C ≤ TA ≤ +85°C 7 40 pA

−40°C ≤ TA ≤ +125°C 45 105 pA

Input Offset Current IOS 7 40 pA

−40°C ≤ TA ≤ +85°C 7 40 pA

−40°C ≤ TA ≤ +125°C 16.5 60 pA

Input Voltage Range −40°C ≤ TA ≤ +125°C −0.1 +3 V

Common-Mode Rejection Ratio CMRR VCM = 0 V to 3 V 118 133 dB

−40°C ≤ TA ≤ +125°C 118 dB

Large Signal Voltage Gain AVO R

−40°C ≤ TA ≤ +125°C 119 dB ∆V

Offset Voltage Drift for All Packages

/∆T −40°C ≤ TA ≤ +125°C 0.01 0.06 μV/°C

Except SOT-23 Offset Voltage Drift for SOT-23 ∆VOS/∆T −40°C ≤ TA ≤ +125°C 0.04 0.15 μV/°C Input Resistance RIN 22.5 TΩ Input Capacitance, Differential Mode C Input Capacitance, Common Mode C

4 pF

INDM

1.7 pF

INCM

OUTPUT CHARACTERISTICS

Output Voltage High VOH R

−40°C ≤ TA ≤ +125°C 4.97 V R

−40°C ≤ TA ≤ +125°C 4.86 V Output Voltage Low VOL R

−40°C ≤ TA ≤ +125°C 15 mV R

−40°C ≤ TA ≤ +125°C 55 mV Short-Circuit Current ISC T Closed-Loop Output Impedance Z

f = 100 kHz, AV = 1 4.2 Ω

OUT

POWER SUPPLY

Power Supply Rejection Ratio PSRR VSY = 4.5 V to 16 V 127 143 dB

−40°C ≤ TA ≤ +125°C 125 dB Supply Current per Amplifier ISY I

−40°C ≤ TA ≤ +125°C 1.5 mA

DYNAMIC PERFORMANCE

Slew Rate SR RL = 10 kΩ, CL = 20 pF, AV = 1 2.5 V/μs Settling Time to 0.1% tS V Overload Recovery Time 50 μs Gain Bandwidth Product GBP RL = 2 kΩ, CL = 20 pF, AV = 1 1.35 MHz Phase Margin ΦM R

NOISE PERFORMANCE

Voltage Noise en p-p 0.1 Hz to 10 Hz 1.2 μV p-p Voltage Noise Density en f = 1 kHz 60 nV/√Hz

= 10 kΩ, VO = 0.5 V to 4.5 V 120 136 dB

= 10 kΩ to VCM 4.97 4.985 V

= 2 kΩ to VCM 4.90 4.93 V

= 10 kΩ to VCM 7.5 10 mV

= 2 kΩ to VCM 32 40 mV

= 25°C ±19 mA

= 0 mA 1.0 1.3 mA

= 2 V step, CL = 20 pF, RL = 1 kΩ, AV = 1 3 μs

= 2 kΩ, CL = 20 pF, AV = 1 70 Degrees

Rev. F | Page 3 of 20

AD8638/AD8639

ELECTRICAL CHARACTERISTICS—16 V OPERATION

VSY = 16 V, VCM = VSY/2, TA = 25°C, unless otherwise noted.

Table 3.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage VOS 3 9 μV

−40°C ≤ TA ≤ +125°C 23 μV

Input Bias Current IB 1 75 pA

Input Offset Current IOS 20 70 pA

Input Voltage Range −40°C ≤ TA ≤ +125°C −0.1 +14 V Common-Mode Rejection Ratio CMRR VCM = 0 V to 14 V 127 142 dB

−40°C ≤ TA ≤ +125°C 127 dB Large Signal Voltage Gain AVO R

−40°C ≤ TA ≤ +125°C 130 dB Offset Voltage Drift for All Packages

∆V

INDM

INCM

OUTPUT CHARACTERISTICS

Output Voltage High VOH R

−40°C ≤ TA ≤ +125°C 15.93 V R

−40°C ≤ TA ≤ +125°C 15.70 V Output Voltage Low VOL R

−40°C ≤ TA ≤ +125°C 60 mV R

−40°C ≤ TA ≤ +125°C 200 mV Short-Circuit Current ISC T Closed-Loop Output Impedance Z

OUT

POWER SUPPLY

Power Supply Rejection Ratio PSRR VSY = 4.5 V to 16 V 127 143 dB

−40°C ≤ TA ≤ +125°C 125 dB Supply Current per Amplifier ISY I

−40°C ≤ TA ≤ +125°C 1.7 mA DYNAMIC PERFORMANCE

Slew Rate SR RL = 10 kΩ, CL = 20 pF, AV = 1 2 V/μs Settling Time to 0.1% tS V Overload Recovery Time 50 μs Gain Bandwidth Product GBP RL = 2 kΩ, CL = 20 pF, AV = 1 1.5 MHz Phase Margin ΦM R

NOISE PERFORMANCE

Voltage Noise en p-p 0.1 Hz to 10 Hz 1.2 μV p-p Voltage Noise Density en f = 1 kHz 60 nV/√Hz

−0.1 V ≤ VCM ≤ +14 V

−40°C ≤ TA ≤ +125°C

−40°C ≤ TA ≤ +85°C

−40°C ≤ TA ≤ +125°C

−40°C ≤ TA ≤ +85°C

−40°C ≤ T

= 10 kΩ, VO = 0.5 V to 15.5 V 130 147 dB

≤ +125°C

3 9 μV 23 μV

4 75 pA 85 250 pA

20 75 pA 50 150 pA

/∆T −40°C ≤ TA ≤ +125°C 0.03 0.06 μV/°C

4 pF

1.7 pF

= 10 kΩ to VCM 15.94 15.96 V

= 2 kΩ to VCM 15.77 15.82 V

= 10 kΩ to VCM 30 40 mV

= 2 kΩ to VCM 120 140 mV

= 25°C ±37 mA

f = 100 kHz, AV = 1 3.0 Ω

= 0 mA 1.25 1.5 mA

= 4 V step, CL = 20 pF, RL = 1 kΩ, AV = 1 4 μs

= 2 kΩ, CL = 20 pF, AV = 1 74 Degrees

Rev. F | Page 4 of 20

AD8638/AD8639

ABSOLUTE MAXIMUM RATINGS

Table 4.

Parameter Rating

Supply Voltage 16 V

Input Voltage GND − 0.3 V to V

+ 0.3 V

SY+

Input Current1 ±10 mA

Differential Input Voltage2 ±VSY

Output Short-Circuit Duration to GND Indefinite

Storage Temperature Range −65°C to +150°C

Operating Temperature Range −40°C to +125°C

Junction Temperature Range −65°C to +150°C

Lead Temperature (Soldering, 60 sec) 300°C

Input pins have clamp diodes to the supply pins. Input current should be

limited to 10 mA or less whenever input signals exceed either power supply rail by 0.3 V.

Inputs are protected against high differential voltages by internal 1 kΩ series

resistors and back-to-back diode-connected N-MOSFETs (with a typical VT of

1.25 V for VCM of 0 V).

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

Table 5. Thermal Resistance

Package Type θ

5-Lead SOT-23 (RJ-5) 230 146 °C/W 8-Lead SOIC_N (R-8) 158 43 °C/W 8-Lead MSOP (RM-8) 206 44 °C/W 8-Lead LFCSP_WD (CP-8-5)2 75 18 °C/W

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 two-layer board.

Exposed pad is soldered to t

he application board.

Unit

ESD CAUTION

Rev. F | Page 5 of 20

AD8638/AD8639

TYPICAL PERFORMANCE CHARACTERISTICS

TA = 25°C, unless otherwise noted.

1400

1200

VSY = 5V 0V  V

 +3V

6000

5000

VSY = 16V 0V  V

 +14V

1000

800

600

400

NUMBER OF AMPL IFIERS

200

–10 10

–5 50

VOS (µV)

06895-003

Figure 5. Input Offset Voltage Distribution

NUMBER OF AMPLIFIERS

VSY = ±2.5V –40°C  T SOIC PACKAGE

 +125°C

4000

3000

2000

NUMBER OF AMPLIFIERS

1000

–10 –5 0 5 10

VOS (µV)

06895-006

Figure 8. Input Offset Voltage Distribution

NUMBER OF AMPLIFIERS

VSY = ±8V –40°C  T SOIC PACKAGE

 +125°C

4 8 12 16 20 24 28 32 36 40

TCVOS (nV/°C)

06895-004

Figure 6. Input Offset Voltage Drift Distribution

10.0 VSY = 5V

–0.5V  V

7.5

5.0

2.5

(µV)

–2.5

–5.0

–7.5

–10.0

–0.5 4

 +3.9V

0 0.5 1 1.5 2.0 2.5 3.0 3.5

VCM (V)

06895-005

Figure 7. Input Offset Voltage vs. Common-Mode Voltage

0 4 8 1216202428323640

TCVOS (nV/°C)

Figure 9. Input Offset Voltage Drift Distribution

10.0

7.5

5.0

2.5

(µV)

–2.5

–5.0

–7.5

–10.0

–0.5

VCM (V)

VSY = 16V –0.5V  V

Figure 10. Input Offset Voltage vs. Common-Mode Voltage

 +14.5V

06895-007

14.513.011.510.08.57.05.54.02.51.0

06895-008

Rev. F | Page 6 of 20

+ 14 hidden pages

ANALOG DEVICES AD8638 Service Manual

FEATURES

APPLICATIONS

GENERAL DESCRIPTION

PIN CONFIGURATIONS

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS

ELECTRICAL CHARACTERISTICS—5 V OPERATION

ELECTRICAL CHARACTERISTICS—16 V OPERATION

ABSOLUTE MAXIMUM RATINGS

THERMAL RESISTANCE

ESD CAUTION

TYPICAL PERFORMANCE CHARACTERISTICS