ANALOG DEVICES AD8505, AD8506, AD8508 Service Manual

20 μA Maximum, Rail-to-Rail I/O,

Zero Input Crossover Distortion Amplifiers

FEATURES

PSRR: 100 dB minimum
CMRR: 105 dB typical
Very low supply current: 20 μA per amplifier maximum

1.8 V to 5 V single supply or ±0.9 V to ±2.5 V dual supply
Rail-to-rail input/output
Low noise: 45 nV/√Hz at 1 kHz

2.5 mV offset voltage maximum
Very low input bias current: 1 pA typical

APPLICATIONS

Pressure and position sensors
Remote security
Bio sensors
IR thermometers
Battery-powered consumer equipment
Hazard detectors

GENERAL DESCRIPTION

The AD8505/AD8506/AD8508 are single, dual, and quad micro­power amplifiers featuring rail-to-rail input/output swings while
operating from a single 1.8 V to 5 V power supply or from dual
±0.9 V to ±2.5 V power supplies. Using a new circuit technology,
these amplifiers offer zero input crossover distortion (excellent
PSRR and CMRR performance) and low bias current while
operating with a supply current of less than 20 µA per amplifier.
This amplifier family offers the lowest noise in its power class.

This combination of features makes the AD8505/AD8506/AD8508
amplifiers ideal choices for battery-powered applications because
they minimize errors due to power supply voltage variations over
the lifetime of the battery and maintain high CMRR even for a rail­to-rail input op amp. Remote battery-powered sensors, handheld
instrumentation, consumer equipment, hazard detection (for
example, smoke, fire, and gas), and patient monitors can benefit
from the features of the AD8505/AD8506/AD8508 amplifiers.

The AD8505/AD8506/AD8508 are specified for both the industrial
temperature range of −40°C to +85°C and the extended industrial
temperature range of −40°C to +125°C. The AD8505 single ampli­fier is available in a tiny 5-lead SOT-23 and a 6-ball WLCSP
packages. The AD8506 dual amplifier is available in 8-lead MSOP
and 8-ball WLCSP packages. The AD8508 quad amplifier is
available in 14-lead TSSOP and 14-ball WLCSP packages. The
AD8505/AD8506/AD8508 are members of a growing series of
zero crossover distortion op amps offered by Analog Devices,
Inc., including the ADA4505-1/ADA4505-2/ADA4505-4, that
operate from a single 1.8 V to 5 V supply or from dual ±0.9 V to
±2.5 V power supplies.

Rev. E

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.

AD8505/AD8506/AD8508

PIN CONFIGURATIONS

BALL A1
INDICATOR

OUT V+

A1 A2

V–

NC

B1 B2

+IN –IN

1

OUT

+IN

V–

AD8505

2

TOP VIEW

(Not to Scale)

3

V+

5

–IN

4

06900-051

Figure 1. 5-Lead SOT-23 (RJ-5) Figure 2. 6-Ball WLCSP (CB-6-7)

OUT A

–IN A

+IN A

V–

1

AD8506

2

TOP VIEW

3

(Not to Scale)

4

8

7

6

5

V+

OUT B

–IN B

+IN B

06900-002

Figure 3. 8-Lead MSOP (RM-8) Figure 4. 8-Ball WLCSP (CB-8-2)

OUT A

–IN A

+IN A

V+

+IN B

–IN B

OUT B

1

2

3

AD8508

TOP VIEW

4

(Not to Scale)

5

6

7

14

13

12

11

10

9

8

OUT D

–IN D

+IN D

V–

+IN C

–IN C

OUT C

06900-045

Figure 5. 14-Lead TSSOP (RU-14) Figure 6. 14-Ball WLCSP (CB-14-1)

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] ©2007–2010 Analog Devices, Inc. All rights reserved.

C1 C2

AD8505

TOP VIEW

(BALL SIDE DOW N)

Not to Scale

NC = NO CONNECT

BALL A1
CORNER

OUT B V+ OUT A

A1 A2 A3

–IN B –IN A

B1 B3

+IN B V– +IN A

C1 C2 C3

AD8506

TOP VIEW

(BALL SI DE DOW N)

Not to Scale

BALL A1
CORNER

OUTD OUTA –INA

A1

A2

–IND V– +INA

B1

B2

+IND +INB

C1

+INC V+ –INB

D1

D2

–INC OUTC

E1

E2

AD8508

TOP VIEW

(BALL SI DE DOWN)

Not to Scale

06900-100

06900-001

A3

B3

C3

D3

OUTB

E3

06900-104

AD8505/AD8506/AD8508

TABLE OF CONTENTS

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

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

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

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

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

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

Electrical Characteristics—1.8 V Operation ............................ 3

Electrical Characteristics—5 V Operation................................ 4

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

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

REVISION HISTORY

5/10—Rev. D to Rev. E

Added AD8505, 6-Ball WLCSP Package ......................... Universal

Changes to Large-Signal Voltage Gain Parameter (Table 1) ....... 4

Changes to Large-Signal Voltage Gain Parameter (Table 2) ....... 5

Changes to Table 4 ............................................................................ 6

Updated Outline Dimensions ....................................................... 19

Changes to Ordering Guide .......................................................... 21

10/09—Rev. C to Rev. D

Added AD8505, 5-Lead SOT-23 Package ....................... Universal

Changes to General Description, Added Figure 1 ....................... 1

Moved Electrical Characteristics—1.8 V Operation Section,

Changes to Supply Current per Amplifier Parameter, Table 1 ..... 3

Moved Electrical Characteristics—5 V Operation Section,

Changes to Supply Current per Amplifier Parameter, Table 2 ..... 4

Changes to Thermal Resistance Section and Table 4 ................... 5

Changes to Figure 20 and Figure 23 ............................................... 8

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

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

3/09—Rev. B to Rev. C

Added AD8508, 14-Ball WLCSP Package ....................... Universal

Updated Outline Dimensions ....................................................... 17

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

10/08—Rev. A to Rev. B

Added WLCSP Package ..................................................... Universal

Added Figure 2; Renumbered Sequentially .................................. 1

Added Input Resistance Parameter ................................................ 3

Changes to Input Capacitance Differential Mode Parameter
Symbol and Input Capacitance Common Mode Parameter

Symbol ................................................................................................ 3

Added Input Resistance Parameter ................................................ 4

Changes to Input Capacitance Differential Mode Parameter
Symbol and Input Capacitance Common Mode Parameter

Symbol ................................................................................................ 4

Rev. E | Page 2 of 20

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

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

Theory of Operation ...................................................................... 13

Applications Information .............................................................. 15

Pulse Oximeter Current Source ............................................... 15

Four-Pole, Low-Pass Butterworth Filter for Glucose

Monitor ........................................................................................ 16

Outline Dimensions ....................................................................... 17

Ordering Guide .......................................................................... 20

Changes to Table 4 ............................................................................. 5

Changes to Figure 46 ...................................................................... 16

Updated Outline Dimensions ....................................................... 17

Added Figure 49 ............................................................................. 17

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

7/08—Rev. 0 to Rev. A

Added AD8508 ................................................................... Universal

Added TSSOP Package ...................................................... Universal

Changes to Features Section and General Description Section .. 1

Added Figure 2; Renumbered Sequentially ................................... 1

Changed Electrical Characteristics Heading to Electrical

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

Changes to Table 1 ............................................................................. 3

Added Electrical Characteristics—1.8 V Operation Heading ..... 4

Changes to Table 2 ............................................................................. 4

Changes to Table 3, Thermal Resistance Section, and Table 4 .... 5

Added T

Characteristics Section ..................................................................... 6

Changes to Figure 3, Figure 4, Figure 6, and Figure 7 .................. 6

Added Figure 11 and Figure 14 ....................................................... 7

Changes to Figure 17 Through Figure 20....................................... 8

Changes to Figure 21 Through Figure 26....................................... 9

Changes to Figure 27, Figure 28, Figure 30, and Figure 31....... 10

Changes to Figure 34, Figure 37, and Figure 38 ......................... 11

Added Figure 39 and Figure 40 .................................................... 12

Added Theory of Operation Section, Figure 41, and

Figure 42 .......................................................................................... 13

Added Figure 43 and Figure 44 .................................................... 14

Added Applications Information Section and Figure 45 .......... 15

Added Figure 46 ............................................................................. 16

Updated Outline Dimensions ....................................................... 17

Added Figure 48 ............................................................................. 17

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

11/07—Revision 0: Initial Version

= 25°C Condition to Typical Performance

A

AD8505/AD8506/AD8508

SPECIFICATIONS

ELECTRICAL CHARACTERISTICS—1.8 V OPERATION

VSY = 1.8 V, VCM = VSY/2, TA = 25°C, RL = 100 k to GND, unless otherwise noted.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage VOS 0 V ≤ VCM ≤ 1.8 V 0.5 2.5 mV

−40°C ≤ TA ≤ +125°C 3.5 mV
Input Bias Current IB 1 10 pA

−40°C ≤ TA ≤ +85°C 100 pA

−40°C ≤ TA ≤ +125°C 600 pA
Input Offset Current IOS 0.5 5 pA

−40°C ≤ TA ≤ +85°C 50 pA

−40°C ≤ TA ≤ +125°C 100 pA
Input Voltage Range −40°C ≤ TA ≤ +125°C 0 1.8 V
Common-Mode Rejection Ratio CMRR 0 V ≤ VCM ≤ 1.8 V 85 100 dB

−40°C ≤ TA ≤ +85°C 85 dB

−40°C ≤ TA ≤ +125°C 80 dB
Large-Signal Voltage Gain AVO

0.05 V ≤ V
R

L

OUT

= 100 kΩ to VCM

≤ 1.75 V,

95 115 dB

−40°C ≤ TA ≤ +125°C 95 dB
Offset Voltage Drift

ΔV

OS

/ΔT

−40°C ≤ T

≤ +125°C 2.5 μV/°C

A

Input Resistance RIN 220 GΩ
Input Capacitance, Differential Mode C
Input Capacitance, Common Mode C

3 pF

INDM

4.2 pF

INCM

OUTPUT CHARACTERISTICS

Output Voltage High VOH R

= 100 kΩ to GND 1.78 1.79 V

L

−40°C ≤ TA ≤ +125°C 1.78 V
R

= 10 kΩ to GND 1.65 1.75 V

L

−40°C ≤ TA ≤ +125°C 1.65 V
Output Voltage Low VOL R

= 100 kΩ to VSY 2 5 mV

L

−40°C ≤ TA ≤ +125°C 5 mV
R

= 10 kΩ to VSY 12 25 mV

L

−40°C ≤ TA ≤ +125°C 25 mV
Short-Circuit Limit ISC V

= VSY or GND ±4.5 mA

OUT

POWER SUPPLY

Power Supply Rejection Ratio PSRR VSY = 1.8 V to 5 V 100 110 dB

−40°C ≤ TA ≤ +85°C 100 dB

−40°C ≤ TA ≤ +125°C 95 dB
Supply Current per Amplifier ISY

AD8506/AD8508 V

= VSY/2 16.5 20 μA

OUT

−40°C ≤ TA ≤ +125°C 25 μA
AD8505 V

= VSY/2 16.5 24 μA

OUT

−40°C ≤ TA ≤ +125°C 27.5 μA

DYNAMIC PERFORMANCE

Slew Rate SR RL = 100 kΩ, CL = 10 pF, G = 1 13 mV/μs
Gain Bandwidth Product GBP RL = 1 MΩ, CL = 20 pF, G = 1 95 kHz
Phase Margin Φ

M

RL = 1 MΩ, CL = 20 pF, G = 1 60 Degrees

NOISE PERFORMANCE

Voltage Noise en p-p f = 0.1 Hz to 10 Hz 2.8 μV p-p
Voltage Noise Density en f = 1 kHz 45 nV/√Hz
Current Noise Density in f = 1 kHz 15 fA/√Hz

Rev. E | Page 3 of 20

AD8505/AD8506/AD8508

ELECTRICAL CHARACTERISTICS—5 V OPERATION

VSY = 5 V, VCM = VSY/2, TA = 25°C, RL = 100 k to GND, unless otherwise noted.

Table 2.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage VOS 0 V ≤ VCM ≤ 5 V 0.5 2.5 mV

−40°C ≤ TA ≤ +125°C 3.5 mV
Input Bias Current IB 1 10 pA

−40°C ≤ TA ≤ +85°C 100 pA

−40°C ≤ TA ≤ +125°C 600 pA
Input Offset Current IOS 0.5 5 pA

−40°C ≤ TA ≤ +85°C 50 pA

−40°C ≤ TA ≤ +125°C 130 pA
Input Voltage Range −40°C ≤ TA ≤ +125°C 0 5 V
Common-Mode Rejection Ratio CMRR 0 V ≤ VCM ≤ 5 V 90 105 dB

−40°C ≤ TA ≤ +85°C 90 dB

−40°C ≤ TA ≤ +125°C 85 dB
Large-Signal Voltage Gain AVO

0.05 V ≤ V
R

= 100 kΩ to VCM

L

≤ 4.95 V,

OUT

−40°C ≤ TA ≤ +125°C 100 dB
Offset Voltage Drift

ΔV

OS

/ΔT

−40°C ≤ T

≤ +125°C 2 μV/°C

A

Input Resistance RIN 220 GΩ
Input Capacitance, Differential Mode C
Input Capacitance, Common Mode C

3 pF

INDM

4.2 pF

INCM

OUTPUT CHARACTERISTICS

Output Voltage High VOH R

= 100 kΩ to GND 4.98 4.99 V

L

−40°C ≤ TA ≤ +125°C 4.98 V
R

= 10 kΩ to GND 4.9 4.95 V

L

−40°C ≤ TA ≤ +125°C 4.9 V
Output Voltage Low VOL R

= 100 kΩ to VSY 2 5 mV

L

−40°C ≤ TA ≤ +125°C 5 mV
R

= 10 kΩ to VSY 10 25 mV

L

−40°C ≤ TA ≤ +125°C 30 mV
Short-Circuit Limit ISC V

= VSY or GND ±45 mA

OUT

POWER SUPPLY

Power Supply Rejection Ratio PSRR VSY = 1.8 V to 5 V 100 110 dB

−40°C ≤ TA ≤ +85°C 100 dB

−40°C ≤ TA ≤ +125°C 95 dB
Supply Current per Amplifier ISY

AD8506/AD8508 V

= VSY/2 15 20 μA

OUT

−40°C ≤ TA ≤ +125°C 25 μA
AD8505 −40°C ≤ TA ≤ +125°C 25.5 μA

DYNAMIC PERFORMANCE

Slew Rate SR RL = 100 kΩ, CL = 10 pF, G = 1 13 mV/μs
Gain Bandwidth Product GBP RL = 1 MΩ, CL = 20 pF, G = 1 95 kHz
Phase Margin ΦM R

= 1 MΩ, CL = 20 pF, G = 1 60 Degrees

L

NOISE PERFORMANCE

Voltage Noise en p-p f = 0.1 Hz to 10 Hz 2.8 μV p-p
Voltage Noise Density en f = 1 kHz 45 nV/√Hz
Current Noise Density in f = 1 kHz 15 fA/√Hz

105 120 dB

Rev. E | Page 4 of 20

AD8505/AD8506/AD8508

ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Rating

Supply Voltage 5.5 V
Input Voltage ±VSY ± 0.1 V
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

1

Input pins have clamp diodes to the supply pins. The input current should

be limited to 10 mA or less whenever the input signal exceeds the power
supply rail by 0.5 V.

2

The differential input voltage is limited to 5 V or the supply voltage, whichever

is less.

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 with its
exposed paddle soldered to a pad, if applicable. Table 4 shows
simulated thermal values for a 4-layer (2S2P) JEDEC standard
thermal test board, unless otherwise specified.

Table 4.

Package Type θJA θJC Unit

5-Lead SOT-23 (RJ-5) 190 92 °C/W
6-Ball WLCSP (CB-6-7) 105 N/A °C/W
8-Lead MSOP (RM-8) 142 45 °C/W
8-Ball WLCSP (CB-8-2) 82 N/A °C/W
14-Lead TSSOP (RU-14) 112 35 °C/W
14-Ball WLCSP (CB-14-1) 64 N/A °C/W

ESD CAUTION

Rev. E | Page 5 of 20

AD8505/AD8506/AD8508

TYPICAL PERFORMANCE CHARACTERISTICS

TA = 25°C, unless otherwise noted.

250

200

VSY = 1.8V

= VSY/2

V

CM

250

200

VSY = 5V
V

= VSY/2

CM

150

100

NUMBER OF AMPLIFIERS

50

0

–4 –1–3 0–2 1 2 3 4

VOS (mV)

Figure 7. Input Offset Voltage Distribution

16

14

12

10

8

6

NUMBER OF AMPLIFIERS

4

2

0

012345678910111213

TCVOS (µV/°C)

VSY = 1.8V
–40°C ≤ T

A

Figure 8. Input Offset Voltage Drift Distribution

2000

1500

≤ +125°C

VSY = 1.8V

150

100

NUMBER OF AMPLIFIERS

50

0

–4 –1–3 0–2 1 2 3 4

06900-003

VOS (mV)

06900-006

Figure 10. Input Offset Voltage Distribution

12

10

8

6

4

NUMBER OF AMPLIFIERS

2

0

012345678910111213

06900-004

TCVOS (µV/°C)

VSY = 5V
–40°C ≤ T

≤ +125°C

A

06900-007

Figure 11. Input Offset Voltage Drift Distribution

2000

1500

VSY = 5V

1000

500

(µV)

0

OS

V

–500

–1000

–1500

–2000

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

VCM (V)

Figure 9. Input Offset Voltage vs. Input Common-Mode Voltage

06900-005

Rev. E | Page 6 of 20

1000

500

(µV)

0

OS

V

–500

–1000

–1500

–2000

012345

VCM (V)

Figure 12. Input Offset Voltage vs. Input Common-Mode Voltage

06900-008