ANALOG DEVICES AD8646, AD8648 Service Manual

24 MHz Rail-to-Rail Amplifiers

www.BDTIC.com/ADI

FEATURES

Offset voltage: 2.5 mV maximum
Single-supply operation: 2.7 V to 5.5 V
Low noise: 8 nV/√Hz
Wide bandwidth: 24 MHz
Slew rate: 11 V/μs
Short-circuit output current: 120 mA
No phase reversal
Low input bias current: 1 pA
Low supply current per amplifier: 2 mA maximum
Unity gain stable

APPLICATIONS

Battery-powered instruments
Multipole filters
ADC front ends
Sensors
Barcode scanners
ASIC input or output amplifiers
Audio amplifiers
Photodiode amplifiers
Datapath/mux/switch control

with Shutdown Option

AD8646/AD8647/AD8648

PIN CONFIGURATIONS

1

OUTA

–INA

2

AD8646

V–

TOP VIEW

3

(Not to Scale)

4

+INA

Figure 1. 8-Lead SOIC and MSOP

1

OUTA

–INA

2

V–

AD8647

3

TOP VIEW

(Not to Scale)

4

5

+INA

SDA

Figure 2. 10-Lead MS

1

1

OUTA

2

2

–INA

3

3

+INA

+INB

–INB

OUTB

V+

AD8648

AD8648

TOP VIEW

TOP VIEW

4

4

(Not to Scale)

(Not to Scale)

5

5

6

6

7

7

Figure 3. 14-Lead SOIC and TSSOP

8

7

6

5

10

9

8

7

6

14

14

13

13

12

12

11

11

10

10

V+

OUTB

–INB

+INB

OP

9

9

8

8

V+

OUTB

–INB

+INB

SDB

OUTD

–IND

+IND

V–

+INC

–INC

OUTC

06527-001

06527-002

06527-003

GENERAL DESCRIPTION

The AD8646 and the AD8647 are the dual, and the AD8648 is
the quad, rail-to-rail, input and output, single-supply amplifiers
featuring low offset voltage, wide signal bandwidth, low input
voltage, and low current noise. The AD8647 also has a low
power shutdown function.

The combination of 24 MHz bandwidth, low offset, low noise,

nd very low input bias current makes these amplifiers useful in

a
a wide variety of applications. Filters, integrators, photodiode
amplifiers, and high impedance sensors all benefit from the
combination of performance features. AC applications benefit

Rev. B

Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her
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.

from the wide bandwidth and low distortion. TheAD8646/
AD8647/AD8648 offer high output drive capability, which is
excellent for audio line drivers and other low impedance
applications.

Applications include portable and low powered instrumenta-

ion, audio amplification for portable devices, portable phone

t
headsets, barcode 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.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] ©2006–2007 Analog Devices, Inc. All rights reserved.

AD8646/AD8647/AD8648

www.BDTIC.com/ADI

TABLE OF CONTENTS

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

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

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

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

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

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

Absolute Maximum Ratings............................................................ 6

Thermal Resistance ...................................................................... 6

REVISION HISTORY

Revision History: AD8646/AD8647/AD8648

10/07—Revision B: Initial Combined Version

Revision History: AD8646

10/07—Rev. 0 to Rev. B

Combined with AD8648....................................................Universal

Added AD8647 ...................................................................Universal

Deleted Figure 4 and Figure 7......................................................... 7

D

eleted Figure 33............................................................................ 11

8/07—Revision 0: Initial Version

Revision History: AD8648

10/0 7 — R e v. A to Re v. B

Combined with AD8646....................................................Universal

Added AD8647 ...................................................................Universal

ESD Caution...................................................................................6

Typical Performance Characteristics..............................................7

Theory of Operation ...................................................................... 15

Power-Down Operation ............................................................ 15

Multiplexing Operation............................................................. 15

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

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

Deleted Figure 7.................................................................................6

D

eleted Figure 11...............................................................................7

Deleted Figure 16 and Figure 17 .....................................................8

Deleted Figure 24...............................................................................9

Deleted Figure 27, Figure 28, Figure 31, and Figure 32 ............ 10

6/07—Rev. 0 to Rev. A

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

Updated Outline Dimensions....................................................... 12

Changes to Ordering Guide.......................................................... 12

1/06—Revision 0: Initial Version

Rev. B | Page 2 of 20

AD8646/AD8647/AD8648

www.BDTIC.com/ADI

SPECIFICATIONS

VSY = 5 V, VCM = VSY/2, TA = +25oC, unless otherwise noted.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage V

OS

−40°C < TA < +125°C 3.2 mV
Offset Voltage Drift ∆VOS/∆T −40°C < TA < +125°C 1.8 7.5 V/°C
Input Bias Current I

B

−40°C < TA < +85°C 50 pA

−40°C < TA < +125°C 550 pA
Input Offset Current I

OS

−40°C < TA < +85°C 50 pA

−40°C < TA < +125°C 250 pA
Input Voltage Range V

CM

Common-Mode Rejection Ratio CMRR VCM = 0 V to 5 V 67 84 dB
Large Signal Voltage Gain AVO R
Input Capacitance

Differential C

DIFF

Common Mode CCM 6.7 pF

OUTPUT CHARACTERISTICS

Output Voltage High V

OH

−40°C < TA < +125°C 4.90 V
I

−40°C < TA < +125°C 4.70 V
Output Voltage Low V

OL

−40°C < TA < +125°C 40 mV
I

−40°C < TA < +125°C 200 mV
Output Current I
Closed-Loop Output Impedance Z

sc

OUT

POWER SUPPLY

Power Supply Rejection Ratio PSRR VSY = 2.7 V to 5.5 V 63 80 dB
Supply Current per Amplifier ISY 1.5 2.0 mA

−40°C < TA < +125°C 2.5 mA
Supply Current Shutdown Mode (AD8647) ISD Shutdown of both amplifiers (AD8647 only) 10

−40°C < TA < +125°C 1

SHUTDOWN INPUTS (AD8647)

Logic High Voltage (Enabled) V
Logic Low Voltage (Power-Down) V
Logic Input Current (Per Pin) I
Output Pin Leakage Current

DYNAMIC PERFORMANCE

INH

INL

IN

Slew Rate SR RL = 2 kΩ 11 V/s
Gain Bandwidth Product GBP 24 MHz
Phase Margin Øm 74 Degrees
Settling Time ts To 0.1% 0.5
Amplifier Turn-On Time (AD8647) t

Amplifier Turn-Off Time (AD8647) t

on

off

VCM = 0 V to 5V 0.6 2.5 mV

0.3 1 pA

0.1 0.5 pA

0 5 V

= 2 kΩ, VO = 0.5 V to 4.5 V 104 116 dB

L

2.5 pF

I

= 1 mA 4.98 4.99 V

OUT

= 10 mA 4.85 4.92 V

OUT

I

= 1 mA 8.4 20 mV

OUT

= 10 mA 78 145 mV

OUT

Short circuit ±120 mA

At 1 MHz, AV = 1 5 Ω

nA
μA

−40°C < TA < +125°C +2.0 V

−40°C < TA < +125°C +0.8 V

−40°C < TA < +125°C 1

−40°C < TA < +125°C (shutdown active) 1

μA
nA

μs
25°C, AV = 1, RL = 1 kΩ (see Figure 44)
25°C, AV = 1, RL = 1 kΩ (see Figure 45)

1
1

μs

μs

Rev. B | Page 3 of 20

AD8646/AD8647/AD8648

www.BDTIC.com/ADI

Parameter Symbol Conditions Min Typ Max Unit

NOISE PERFORMANCE

Peak-to-Peak Noise en p-p 0.1 Hz to 10 Hz 2.3 V
Voltage Noise Density e
f = 10 kHz 6 nV/√Hz
Channel Separation CS f = 10 kHz −115 dB
f = 100 kHz −110 dB
Total Harmonic Distortion Plus Noise THD + N V p-p = 0.1 V, RL = 600 Ω, f = 25 kHz, TA = 25°C
A
A

n

f = 1 kHz 8 nV/√Hz

= +1 0.010 %

V

= −10 0.021 %

V

Rev. B | Page 4 of 20

AD8646/AD8647/AD8648

www.BDTIC.com/ADI

VSY = 2.7 V, VCM = VSY/2, TA = +25oC, unless otherwise noted.

Table 2.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage V

OS

−40°C < TA < +125°C 3.2 mV
Offset Voltage Drift ∆VOS/∆T −40°C < TA < +125°C 1.8 7.0 V/°C
Input Bias Current I

B

−40°C < TA < +85°C 50 pA

−40°C < TA < +125°C 550 pA
Input Offset Current I

OS

−40°C < TA < +85°C 50 pA

−40°C < TA < +125°C 250 pA
Input Voltage Range V

CM

Common-Mode Rejection Ratio CMRR VCM = 0 V to 2.7 V 62 79 dB
Large Signal Voltage Gain AVO R

Input Capacitance

Differential C

DIFF

Common Mode CCM 7.8 pF

OUTPUT CHARACTERISTICS

Output Voltage High V

OH

−40°C < TA < +125°C 2.60 V
Output Voltage Low V

OL

−40°C < TA < +125°C 30 mV
Output Current I
Closed-Loop Output Impedance Z

OUT

OUT

POWER SUPPLY

Power Supply Rejection Ratio PSRR VSY = 2.7 V to 5.5 V 63 80 dB
Supply Current per Amplifier ISY 1.6 2.0 mA

−40°C < TA < +125°C 2.5 mA
Supply Current Shutdown Mode (AD8647) ISD Shutdown of both amplifiers (AD8647 only) 10 nA

SHUTDOWN INPUTS (AD8647)

Logic High Voltage (Enabled) V
Logic Low Voltage (Power-Down) V
Logic Input Current (Per Pin) V
Output Pin Leakage Current

DYNAMIC PERFORMANCE

INH

INL

IN

Slew Rate SR RL = 2 kΩ 11 V/s
Gain Bandwidth Product GBP 24 MHz
Phase Margin Ø

m

Settling Time ts To 0.1% 0.3

Amplifier Turn-On Time (AD8647) t
Amplifier Turn-Off Time (AD8647) t

on

off

NOISE PERFORMANCE

Peak-to-Peak Noise en p-p 0.1 Hz to 10 Hz 2.3 V
Voltage Noise Density e

n

f = 10 kHz 6 nV/√Hz

Channel Separation CS f = 10 kHz −115 dB
f = 100 kHz −110 dB

VCM = 0 V to 2.7 V 0.6 2.5 mV

0.2 1 pA

0.1 0.5 pA

0 2.7 V

= 2 kΩ, VO = 0.5 V to 2.2 V 95 102 dB

L

2.5 pF

I

= 1 mA 2.65 2.68 V

OUT

I

= 1 mA 11 25 mV

OUT

Short circuit ±63 mA

At 1 MHz, AV = 1 5 Ω

−40°C < TA < +125°C 1 µA

−40°C < TA < +125°C +2.0 V

−40°C < TA < +125°C +0.8 V

−40°C < TA < +125°C 1 µA

−40°C < TA < +125°C (shutdown active) 1 nA

53 Degrees

μs
25°C, AV = 1, RL = 1 kΩ (see Figure 41)
25°C, AV = 1, RL = 1 kΩ (see Figure 42)

1.2
1

μs

μs

f = 1 kHz 8 nV/√Hz

Rev. B | Page 5 of 20

AD8646/AD8647/AD8648

www.BDTIC.com/ADI

ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Rating

Supply Voltage 6 V
Input Voltage GND to V
Differential Input Voltage ±3 V
Output Short Circuit to GND Indefinite
Storage Temperature Range −65°C to +150°C
Operating Temperature Range −40°C to +125°C
Lead Temperature (Soldering 60 sec) 300°C
Junction Temperature 150°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.

SY

THERMAL RESISTANCE

θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.

Table 4. Thermal Resistance

Package Type θJA θ

8-Lead SOIC_N 125 43 °C/W
8-Lead MSOP 210 45 °C/W
10-Lead MSOP 200 44 °C/W
14-Lead SOIC_N 120 36 °C/W
14-Lead TSSOP 180 35 °C/W

ESD CAUTION

Unit

JC

Rev. B | Page 6 of 20