Datasheet AD8290 Datasheet (ANALOG DEVICES)

G = 50, CMOS Sensor Amplifier

www.BDTIC.com/ADI

FEATURES

Supply voltage range: 2.6 V to 5.5 V
Low power

1.2 mA + 2× excitation current

0.5 μA shutdown current
Low input bias current: ±100 pA
High CMRR: 120 dB
Space savings: 16-lead, 3.0 mm × 3.0 mm × 0.55 mm LFCSP
Excitation current

300 μA to 1300 μA range
Set with external resistor

APPLICATIONS

Bridge and sensor drives
Portable electronics

FUNCTIONAL BLOCK DIAGRAM

R

SET

13

15

C

BRIDGE

14

NC NCNCNC NC NC

GENERAL DESCRIPTION

The AD8290 contains both an adjustable current source to
drive a sensor and a difference amplifier to amplify the signal
voltage. The amplifier is set for a fixed gain of 50. The AD8290
is an excellent solution for both the drive and the sensing aspects
required for pressure, temperature, and strain gage bridges.

In addition, because the AD8290 operates with low power,

orks with a range of low supply voltages, and is available in a

w
low profile package, it is suitable for drive/sense circuits in
portable electronics as well.

The AD8290 is available in a lead free 3.0 mm × 3.0 mm ×

0.55 mm p
temperature range of −40°C to +85°C.

C

FILTER

11 6 5 3

V

REF

ENBL

AD8290

with Current Excitation

AD8290

ackage and is operational over the industrial

V

CC

2

10

GND

161 1297 8

4

ANTI-

ALIASI NG

FILTER

ADC

Figure 1.

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.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] ©2007–2008 Analog Devices, Inc. All rights reserved.

06745-001

AD8290

www.BDTIC.com/ADI

TABLE OF CONTENTS

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

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

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

Functional Block Diagram .............................................................. 1

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

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

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

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

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

Pin Configuration and Function Descriptions............................. 6

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

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

Amplifier...................................................................................... 14

High Power Supply Rejection (PSR) and Common-Mode

Rejection (CMR) ........................................................................ 14

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

Current Source............................................................................ 15

Applications Information.............................................................. 16

Typical C o n ne ctions .................................................................. 16

Current Excitation...................................................................... 16

Enable/Disable Function ........................................................... 16

Output Filtering.......................................................................... 16

Clock Feedthrough..................................................................... 16

Maximizing Performance Through Proper Layout ............... 17

Power Supply Bypassing ............................................................ 17

Dual-Supply Operation............................................................. 17

Pressure Sensor Bridge Application......................................... 18

Temperature Sensor Application.............................................. 19

ADC/Microcontroller................................................................ 19

Outline Dimensions ....................................................................... 20

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

REVISION HISTORY

2/08—Rev. SpA to Rev. B

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

Changes to Amplifier Section and Figure 43.............................. 14

Changes to Current Source Section ............................................. 15

Changes to Current Excitation Section, Output Filtering

Section, Clock Feedthrough Section, and Figure 45.................. 16

Changes to Figure 46...................................................................... 17

8/07—Revision SpA

7/07—Revision 0: Initial Version

Rev. B | Page 2 of 20

AD8290

www.BDTIC.com/ADI

SPECIFICATIONS

VCC = 2.6 V to 5.0 V, TA = 25°C, C
otherwise noted.

Table 1.

Parameter Test Conditions Min Typ Max Unit

COMMON-MODE REJECTION RATIO (CMRR)

CMRR DC 110 120 dB

NOISE

Amplifier and VREF Input referred, f = 0.1 Hz to 10 Hz 0.75 μV p-p

VOLTAGE OFFSET

Output Offset

Output Offset TC −40°C < TA < +85°C −300 ±50 +300 μV/°C
PSR 120 dB

INPUT CURRENT

Input Bias Current −1000 ±100 +1000 pA
Input Offset Current −2000 ±200 +2000 pA

DYNAMIC RESPONSE

Small Signal Bandwidth –3 dB

GAIN

Gain 50 V/V
Gain Error −1.0 ±0.5 +1.0 %
Gain Nonlinearity ±0.0075 %
Gain Drift −40°C < TA < +85°C −25 ±15 +25 ppm/°C

INPUT

Differential Input Impedance 50||1 MΩ||pF
Input Voltage Range 0.2 VCC − 1.7 V

OUTPUT

Output Voltage Range

Output Series Resistance 10 ± 20% kΩ

CURRENT EXCITATION

Excitation Current Range Excitation current = 0.9 V/R
Excitation Current Accuracy −1.0 +1.0 %
Excitation Current Drift −40°C < TA < +85°C −250 ±50 +250 ppm/°C
External Resistor for Setting

Excitation Current (R

Excitation Current Power

Supply Rejection
Excitation Current Pin Voltage 0 VCC − 1.0 V
Excitation Current Output Resistance 100 MΩ
Required Capacitor from Ground to

Excitation Current Pin (C

ENABLE

ENBL High Level VCC < 2.9 V VCC − 0.5 V
V
ENBL Low Level GND 0.8 V
Start-Up Time for ENBL 5.0 ms

SET

)

BRIDGE

= 6.8 nF, output antialiasing capacitor = 68 nF, R

FILTER

− V

− 1.7 V

CC

− V

INN

INN

)

) +

SET

Input voltage (V
range of 0.2 V to V

Reference is internal and set to
900 mV nominal

With external filter capacitors,

= 6.8 nF and output

C

FILTER

antialiasing capacitor = 68 nF

= Gain × (V

V

OUT

Output Offset

692 3000 Ω

−2.0 +0.2 +2.0 μA/V

0.1 μF

)

> 2.9 V 2.4 V

CC

INP

INP

= 3 kΩ, common-mode input = 0.6 V, unless

SET

865 900 935 mV

0.25 kHz

0.075 V

300 1300 μA

− 0.075 V

CC

CC

CC

V
V

Rev. B | Page 3 of 20

AD8290

www.BDTIC.com/ADI

Parameter Test Conditions Min Typ Max Unit

POWER SUPPLY

Operating Range 2.6 5.5 V
Quiescent Current

Shutdown Current 0.5 10 μA

TEMPERATURE RANGE

For Operational Performance −40 +85 °C

1.2 + 2×
citation current

ex

1.8 + 2×
excitation current

mA

Rev. B | Page 4 of 20

AD8290

www.BDTIC.com/ADI

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

Supply Voltage 6 V
Input Voltage +V
Differential Input Voltage
Output Short-Circuit Duration to GND Indefinite
Storage Temperature Range −65°C to +150°C
Operating Temperature Range −40°C to +85°C
Junction Temperature Range −65°C to +150°C
Lead Temperature (Soldering, 10 sec) 300°C

1

Differential input voltage is limited to ±5.0 V, the supply voltage, or

whichever is less.

1

±V

SUPPLY

SUPPLY

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.

Table 3.

Package Type θ

16-Lead LFCSP (0.55 mm) 42.5 7.7 °C/W

JA

θ

JC

Unit

ESD CAUTION

Rev. B | Page 5 of 20

AD8290

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PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

NC

VINP

VINN

IOUT

16

14

15

13

NC

1

2

3

4

AD8290

TOP

VIEW

(Not to Scale)

5

6

7

NC

CF1

CF2

VCC

ENBL

VOUT

NC = NO CONNECT

Figure 2. Pin Configuration

Table 4. Pin Function Descriptions

Pin No. Mnemonic Description

1 NC Tie to Ground1 or Pin 16.
2 VCC Positive Power Supply Voltage.
3 ENBL Logic 1 enables the part, and Logic 0 disables the part.
4 VOUT

5 CF2 Tie one end of the C
6 CF1 Tie the other end of the C
7 NC Tie to Ground.
8 NC Tie to Ground.
9 NC Tie to Ground.

Open End of Internal 10 kΩ Resistor. Tie one end of external antialiasing filt
the other end to ground.

1

1

1

1

(68 nF) that is in parallel with the internal gain resistor to this pin.

FILTER

(68 nF) that is in parallel with the internal gain resistor to this pin.

FILTER

10 GND Ground1 or Negative Power Supply Voltage.
11 RSET Tie one end of Resistor R
12 NC Tie to Ground.

1

13 IOUT Excitation Current Output. Tie one end of C

to this pin to set the excitation current and tie the other end of Resistor R

SET

BRIDGE

14 VINN Negative Input Terminal.
15 VINP Positive Input Terminal.
16 NC Tie to Ground1 or Pin 1.
17/Pad NC Pad should be floating and not tied to any potential.

1

During dual-supply operation, ground becomes the negative power supply voltage.

NC

12

RSET

11

GND

10

NC

9

8

NC

06745-002

er capacitor (6.8 nF) to this pin, and tie

(0.1 μF) to this pin and tie the other end of C

BRIDGE

to Pin 10.

SET

to ground.

1

Rev. B | Page 6 of 20

AD8290

www.BDTIC.com/ADI

TYPICAL PERFORMANCE CHARACTERISTICS

35

25

30

25

20

15

UNITS ( %)

10

5

0

892 894 896 898 900 902 904 906 908

OUTPUT VOLTAGE (mV)

Figure 3. Output Offset Voltage at 2.6 V Supply

35

30

25

20

15

UNITS (%)

10

5

20

15

UNITS (%)

10

5

0

0.2988

06745-003

Figure 6. Excitation Output Current for 3 kΩ R

0.2994

0.2991

0.2997

EXCITATI ON CURRENT (mA)

0.3000

0.3003

0.3006

0.3009

at 2.6 V Supply

SET

0.3012

06745-006

25

20

15

UNITS (%)

10

5

0

892 894 896 898 900 902 904 906 908

OUTPUT VOLTAGE (mV)

Figure 4. Output Offset Voltage at 3.6 V Supply

35

30

25

20

15

UNITS (%)

10

5

0

892 894 896 898 900 902 904 906 908

OUTPUT VOLTAGE (mV)

Figure 5. Output Offset Voltage at 5.0 V Supply

0

0.2988

06745-004

Figure 7. Excitation Output Current for 3 kΩ R

0.2994

0.2991

0.2997

EXCITATI ON CURRENT (mA)

0.3000

0.3003

0.3006

0.3009

at 3.6 V Supply

SET

0.3012

06745-007

25

20

15

UNITS ( %)

10

5

0

0.2988

06745-005

Figure 8. Excitation Output Current for 3 kΩ R

0.2994

0.2991

0.2997

EXCITATI ON CURRENT (mA)

0.3000

0.3003

0.3006

0.3009

at 5.0 V Supply

SET

0.3012

06745-008

Rev. B | Page 7 of 20

AD8290

www.BDTIC.com/ADI

25

25

20

15

UNITS (%)

10

5

0

1.296 1.297 1.298 1.299 1.300 1.301 1.302 1.303 1.304 1.305

EXCITATI ON CURRENT (mA)

Figure 9. Output Excitation Current for 692 Ω R

25

20

15

UNITS (%)

10

5

at 2.6 V Supply

SET

20

15

UNITS (%)

10

5

0

06745-009

–0.60 –0.56 –0. 52 –0.48 –0.44 –0.40 –0.36 –0.32 –0.28

GAIN ERROR (%)

06745-012

Figure 12. Percent Gain Error at 2.6 V Supply

25

20

15

UNITS (%)

10

5

0

1.296 1.297 1.298 1.299 1.300 1.301 1.302 1.303 1.304 1.305

EXCITATI ON CURRENT (mA)

Figure 10. Output Excitation Current for 692 Ω R

25

20

15

UNITS (%)

10

5

0

1.296 1.297 1.298 1.299 1.300 1.301 1.302 1.303 1.304 1.305

EXCITATI ON CURRENT (mA)

Figure 11. Output Excitation Current for 692 Ω R

at 3.6 V Supply

SET

at 5.0 V Supply

SET

0

06745-010

–0.60 –0.56 –0.52 –0.48 –0. 44 –0.40 –0. 36 –0.32 –0. 28

GAIN ERROR (%)

06745-013

Figure 13. Percent Gain Error at 3.6 V Supply

25

20

15

UNITS (%)

10

5

0

06745-011

–0.60 –0.56 –0.52 –0.48 –0. 44 –0.40 –0. 36 –0.32 –0. 28

GAIN ERROR (%)

06745-014

Figure 14. Percent Gain Error at 5.0 V Supply

Rev. B | Page 8 of 20

AD8290

www.BDTIC.com/ADI

40

35

30

50

40

25

20

UNITS (%)

15

10

5

0

0.0030

0.0035

0.0040

0.0045
NONLINEARI TY (%)

0.0050

0.0055

0.0060

0.0065

0.0070

06745-026

Figure 15. Percent Nonlinearity at 2.6 V Supply

35

30

25

20

15

UNITS (%)

10

5

0

0.0030

0.0035

0.0040

0.0045
NONLINEARI TY (%)

0.0050

0.0055

0.0060

0.0065

0.0070

06745-027

Figure 16. Percent Nonlinearity at 3.6 V Supply

45

40

35

30

25

20

UNITS ( %)

15

10

5

0

0.0030

0.0045

0.0060

0.0075
NONLINEARI TY (%)

0.0090

0.0105

0.0120

0.0135

0.0150

06745-028

Figure 17. Percent Nonlinearity at 5.0 V Supply

30

UNITS (%)

20

10

0

–35–155 25456585105125

DRIFT (µV/ °C)

06745-031

Figure 18. Output Offset Voltage Drift from −40°C to +85°C at 2.6 V Supply

50

40

30

UNITS ( %)

20

10

0

–35–155 25456585105125

DRIFT (µV/ °C)

06745-032

Figure 19. Output Offset Voltage Drift from −40°C to +85°C at 3.6 V Supply

50

40

30

UNITS (%)

20

10

0

–35–155 25456585105125

DRIFT (µV/ °C)

06745-033

Figure 20. Output Offset Voltage Drift from −40°C to +85°C at 5.0 V Supply

Rev. B | Page 9 of 20

AD8290

www.BDTIC.com/ADI

45

40

35

30

25

20

UNITS (%)

15

10

5

0

5 203550658095110125

DRIFT (ppm/°C)

Figure 21. Excitation Current Drift from −40°C to +85°C at

= 3 kΩ

2.6 V Supply,

45

40

35

30

25

20

UNITS (%)

15

10

5

0

5 203550658095110125

R

SET

DRIFT (ppm/°C)

Figure 22. Excitation Current Drift from −40°C to +85°C at

= 3 kΩ

3.6 V Supply,

45

40

35

30

25

20

UNITS (%)

15

10

5

0

5 203550658095110125

R

SET

DRIFT (ppm/°C)

Figure 23. Excitation Current Drift from −40°C to +85°C at

5.0 V Supply,

R

= 3 kΩ

SET

06745-035

06745-036

06745-037

40

35

30

25

20

UNITS (%)

15

10

5

0

10 20 30 40 50 60 70 80 90

DRIFT (ppm/°C)

Figure 24. Excitation Current Drift from −40°C to +85°C at

= 692 Ω

2.6 V Supply,

40

35

30

25

20

UNITS (%)

15

10

5

0

10 20 30 40 50 60 70 80 90

R

SET

DRIFT (ppm/°C)

Figure 25. Excitation Current Drift from −40°C to +85°C at

= 692 Ω

3.6 V Supply,

40

35

30

25

20

UNITS (%)

15

10

5

0

10 20 30 40 50 60 70 80 90

R

SET

DRIFT (ppm/°C)

Figure 26. Excitation Current Drift from −40°C to +85°C at

= 692 Ω

5.0 V Supply,

R

SET

06745-039

06745-040

06745-041

Rev. B | Page 10 of 20

AD8290

www.BDTIC.com/ADI

40

35

30

25

100

20

UNITS (%)

15

10

5

0

–16.0 –15.5 –15.0 –14.5 –14.0 –13.5 –13.0 –12.5 –12.0

DRIFT (ppm/°C)

Figure 27. Gain Drift from −40°C to +85°C at 2.6 V Supply

40

35

30

25

20

UNITS (%)

15

10

5

0

–16.0 –15.5 –15.0 –14.5 –14.0 –13.5 –13.0 –12.5 –12.0

DRIFT (ppm/°C)

Figure 28. Gain Drift from −40°C to +85°C at 3.6 V Supply

40

35

30

25

20

UNITS (%)

15

10

5

0

–16.0 –15.5 –15.0 –14.5 –14.0 –13.5 –13.0 –12.5 –12.0

DRIFT (ppm/°C)

Figure 29. Gain Drift from −40°C to +85°C at 5.0 V Supply

10

GAIN (V/V)

1

1 10 100 1k 10k

06745-045

FREQUENCY (Hz)

06745-018

Figure 30. Frequency Response for Supply Range of 2.6 V to 5.0 V

(External

310

308

306

304

302

300

298

296

EXCITATI ON CURRENT (µA)

294

292

290

2.50 2.75 3.00 3.25 3.50 3. 75 4.00 4.25 4.50 4.75 5.00 5.25 5.50

06745-046

FILTER

POWER SUPPLY (V)

06745-019

= 6.8 nF, Antialiasing Capacitor = 68 nF)

C

Figure 31. Low Excitation Current vs. Power Supply

1.310

1.308

1.306

1.304

1.302

1.300

1.298

1.296

EXCITATI ON CURRENT (mA)

1.294

1.292

1.290

2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4. 50 4.75 5.00 5.25 5.50

06745-047

POWER SUPPLY (V)

06745-020

Figure 32. High Excitation Current vs. Power Supply

Rev. B | Page 11 of 20

AD8290

www.BDTIC.com/ADI

310

50.0

305

300

295

290

EXCITATI ON CURRENT (µA)

285

280

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Figure 33. Low Excitation Current vs. E

2.6V SUPPLY

3.6V SUPPLY

5.0V SUPPLY

PIN VOLT AGE (V)

xcitation Current Pin Voltage

1.32

1.31

1.30

1.29

1.28

EXCITATI ON CURRENT (mA)

1.27

1.26

Figure 34. High Excitation Current v

2.6V SUPPLY

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

PIN VOLT AGE (V)

3.6V SUPPL Y

5.0V SUPPL Y

s. Excitation Current Pin Voltage

0.905

0.904

0.903

0.902

0.901

0.900

0.899

5.0V SUPPLY

OUTPUT OFFSET (V)

0.898

0.897

0.896

0.895
–45 –35 –25 –15 –5 5 15 25 35 45 55 65 75 85 95

TEMPERATURE (°C)

Figure 35. Output Offset Voltage v

2.6V SUPPLY

3.6V SUPPL Y

s. Temperature

49.9

49.8

GAIN (V/V)

49.7

49.6

49.5
–55 –45 –35 –25 –15 –5 5 15 25 35 45 55 65 75 85 95

06745-021

5V SUPPLY

TEMPERATURE (°C)

2.6V SUPPL Y

3.6V SUPPL Y

06745-052

Figure 36. Gain vs. Temperature

0.305

0.304

0.303

0.302

0.301

0.300

0.299

0.298

EXCITATI ON CURRENT (mA)

0.297

0.296

0.295
–45 –35 –25 –15 –5 5 15 25 35 45 55 65 75 85 95

06745-022

5.0V SUPPL Y

TEMPERATURE (°C)

Figure 37. Excitation Current vs. Temperature, R

2.6V SUPPLY

3.6V SUPPL Y

= 3 kΩ

SET

06745-038

1.315

1.310

1.305

1.300

1.295

EXCITATI ON CURRENT (mA)

1.290

1.285

06745-034

2.6V SUPPLY

–45 –35 –25 –15 –5 5 15 25 35 45 55 65 75 85 95

TEMPERATURE (°C)

Figure 38. Excitation Current vs. Temperature, R

5.0V SUPPL Y

3.6V SUPPL Y

= 692 Ω

SET

06745-042

Rev. B | Page 12 of 20

AD8290

www.BDTIC.com/ADI

1.5

1.4

1.3

1.2

3.6V SUPPL Y

1.1

1.0

0.9

QUIESCENT CURRENT (mA)

0.8

0.7

0.6
–45 –35 –25 –15 –5 5 15 25 35 45 55 65 75 85 95

5.0V SUPPL Y

2.6V SUPPL Y

TEMPERATURE (°C)

06745-043

Figure 39. Quiescent Current vs. Temperature (Excludes 2× Excitation Current)

INPUT-REF ERRED NOISE (100nV/DI V)

TIME (10s/ DIV)

06745-049

Figure 40. 0.01 Hz to 10 Hz Input-Referred Noise

1000

100

NOISE (nV Hz)

10

1

0.01 0.1 1 10 100 1000

FREQUENCY (Hz)

Figure 41. Input-Referred Noise vs. Frequency

1.0

0.9

0.8

0.7

0.6

0.5

0.4

VOLTS (V)

0.3

0.2

0.1

0

–0.1

–10 –5 0 5 10 15 20

ENBL PIN

VOLTAGE

(0V TO 5V)

OUTPUT OFFSET
VOLTAGE

TIME (ms)

Figure 42. ENBL Pin Voltage for 5.0 V Supply vs.

Output Offset Voltage St

art-Up Time

06745-051

06745-050

Rev. B | Page 13 of 20

AD8290

V

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THEORY OF OPERATION

AMPLIFIER

The amplifier of the AD8290 is a precision current-mode
correction instrumentation amplifier. It is internally set to a
fixed gain of 50. The current-mode correction topology results
in excellent accuracy.

Figure 43 shows a simplified diagram illustrating the basic
o

peration of the instrumentation amplifier within the AD8290
(without correction). The circuit consists of a voltage-to-current
amplifier (M1 to M6), followed by a current-to-voltage amplifier
(R2 and A1). Application of a differential input voltage forces a
current through R1, resulting in a conversion of the input
voltage to a signal current. Transistors M3 to M6 transfer twice
the signal current to the inverting input of the op amp, A1. A1
and R2 form a current-to-voltage converter to produce a rail-to­rail output voltage, V

Op Amp A1 is a high precision auto-zero amplifier. This

mplifier preserves the performance of the autocorrecting,

a
current-mode amplifier topology while offering the user a true
voltage-in, voltage-out instrumentation amplifier. Offset errors
are corrected internally.

An internal 0.9 V reference voltage is applied to the noninverting

nput of A1 to set the output offset level. External Capacitor

i

is used to filter out correction noise.

C

FILTER

VINP

OUT

.

CC

VINN

M5

I – I

R1

M3 M4

– V

R1

INN

I

)

M2

I

M1

R1

(V

INP

I

=

R1

M6

I – I

I + I

HIGH POWER SUPPLY REJECTION (PSR) AND COMMON-MODE REJECTION (CMR)

PSR and CMR indicate the amount that the offset voltage of an
amplifier changes when its common-mode input voltage or power
supply voltage changes. The autocorrection architecture of the
AD8290 continuously corrects for offset errors, including those
induced by changes in input or supply voltage, resulting in
exceptional rejection performance. The continuous autocorrection
provides great CMR and PSR performances over the entire
operating temperature range (−40°C to +85°C).

1/f NOISE CORRECTION

Flicker noise, also known as 1/f noise, is noise inherent in the
physics of semiconductor devices and decreases 10 dB per decade.
The 1/f corner frequency of an amplifier is the frequency at which
the flicker noise is equal to the broadband noise of the amplifier. At
lower frequencies, flicker noise dominates causing large errors
in low frequency or dc applications.

Flicker noise appears as a slowly varying offset error that is

educed by the autocorrection topology of the AD8290, allowing

r
the AD8290 to have lower noise near dc than standard low
noise instrumentation amplifiers.

C

FILTER

R2

R1

2I

R1

R1

V

BIAS

V

REF

A1

= 0.9V

R3

= V

V

OUT

REF

2R2

V

– V

INP

+

R1

INN

2I

EXTERNAL

2I

Figure 43. Simplified Schematic of the Ins

trumentation Amplifier Within the AD8290

Rev. B | Page 14 of 20

06745-023

AD8290

www.BDTIC.com/ADI

CURRENT SOURCE

The AD8290 generates an excitation current that is
programmable with an external resistor, R

, as shown in

SET

Figure 44. A1 and M1 are configured to produce 0.9 V across
R

, which is based on an internal 0.9 V reference and creates a

SET

current equal to 0.9 V/R

internal to the AD8290. This current

SET

is passed to a precision current mirror and a replica of the current
is sourced from the IOUT pin. This current can be used for the
excitation of a sensor bridge. C

is used to filter noise from

BRIDGE

the current excitation circuit.

V

= 0.9V

REF

Figure 44. Current Excitation

PRECISION CURRENT

A1

M1

RSETGND

R

SET

MIRROR

SENSOR

BRIDGE

IOUT

C

BRIDGE

06745-024

Rev. B | Page 15 of 20

AD8290

www.BDTIC.com/ADI

APPLICATIONS INFORMATION

TYPICAL CONNECTIONS

Figure 45 shows the typical connections for single-supply
operation when used with a sensor bridge.

CURRENT EXCITATION

In Figure 45, R
the IOUT pin. The formula for the excitation current I

= (900/R

I

OUT

where R

SET

(RSET).

The AD8290 is internally set by the factory to provide the
c

urrent excitation described by the previous formula (within the
tolerance range listed in Tab le 1 ). The range of R
3 kΩ, resulting in a corresponding I
respectively.

is used to set the excitation current sourced at

SET

is

OUT

) mA

SET

is the resistor between Pin 10 (GND) and Pin 11

is 692 Ω to

SET

of 1300 μA to 300 μA,

OUT

ENABLE/DISABLE FUNCTION

Pin 3 (ENBL) provides the enabling/disabling function of the
AD8290 to conserve power when the device is not needed. A
Logic 1 turns the part on and allows it to operate normally. A
Logic 0 disables the output and excitation current and reduces
the quiescent current to less than 10 μA.

The turn-on time upon switching Pin 3 high is dominated

y the output filters. When the device is disabled, the output

b
becomes high impedance, enabling the muxing application of
multiple AD8290 instrumentation amplifiers.

For bandwidths greater than 10 Hz, an additional single-pole
R

C filter of 235 Hz is required on the output, which is also
recommended when driving an ADC requiring an antialiasing
filter. Internal to the AD8290 is a series 10 kΩ resistor at the
output (R3 in
t

o ground produces an RC filter of 235 Hz on the output as well.

Figure 43) and using an external 68 nF capacitor

These two filters produce an overall bandwidth of approximately
160 Hz for the output signal.

In addition, when driving low impedances, the internal series
10 kΩ r

esistor creates a voltage divider at the output. If it is
necessary to access the output of the internal amplifier prior
to the 10 kΩ resistor, it is available at the CF2 pin.

For applications with low bandwidths (<10 Hz), only the first

lter capacitor (C

fi

) is required. In this case, the high

FILTER

frequency noise from the auto-zero amplifier (output amplifier)
is not filtered before the following stage.

CLOCK FEEDTHROUGH

The AD8290 uses two synchronized clocks to perform
autocorrection. The input voltage-to-current amplifiers
are corrected at 60 kHz.

Trace amounts of these clock frequencies can be observed at

he output. The amount of feedthrough is dependent upon the

t
gain because the autocorrection noise has an input- and output­referred term. The correction feedthrough is also dependent
upon the values of the external capacitors, C2 and C

FILTER

.

OUTPUT FILTERING

Filter Capacitor C
switching noise present at the output. The recommended
bandwidth of the filter created by C
100 kΩ is 235 Hz. Select C

= 1/(235 × 2 × π × 100 kΩ) = 6.8 nF

C

FILTER

is required to limit the amount of

FILTER

and an internal

FILTER

based on

FILTER

692Ω TO 3kΩ

C

BRIDGE

NC = NO CONNECT

NOTES
LAYOUT CONSIDERATIO NS:

1. KEEP C1 CLO SE TO PIN 2 AND PIN 10.

2. KEEP R

CLOSE TO PIN 11.

SET

R

SET

Figure 45. Typical Single-Supply Connections

C

FILTER

6.8nF

11

RSET

13

IOUT

14

VINN

15

VINP

NC NCNCNC NC NC

Rev. B | Page 16 of 20

6

AD8290

7

8

5.0V

5

3

ENBL

CF2CF1

2

VCC

GND

VOUT V

161 129

C1

0.1µF

10

4

C2
68nF

OUT

06745-025

AD8290

www.BDTIC.com/ADI

MAXIMIZING PERFORMANCE THROUGH PROPER LAYOUT

To achieve the maximum performance of the AD8290, care
should be taken in the circuit board layout. The PCB surface
must remain clean and free of moisture to avoid leakage currents
between adjacent traces. Surface coating of the circuit board
reduces surface moisture and provides a humidity barrier,
reducing parasitic resistance on the board.

should be placed close to RSET (Pin 11) and GND (Pin 10).

R

SET

The paddle on the bottom of the package should not be connected
to any potential and should be floating.

For high impedance sources, the PCB traces from the AD8290

nputs should be kept to a minimum to reduce input bias

i
current errors.

POWER SUPPLY BYPASSING

The AD8290 uses internally generated clock signals to perform
autocorrection. As a result, proper bypassing is necessary to
achieve optimum performance. Inadequate or improper bypassing
of the supply lines can lead to excessive noise and offset voltage.
A 0.1 μF surface-mount capacitor should be connected between
Pin 2 (VCC) and Pin 10 (GND) when operating with a single
supply and should be located as close as possible to those two pins.

R

692Ω TO 3kΩ

SET

–1.8V

11

RSET

13

IOUT

14

VINN

DUAL-SUPPLY OPERATION

The AD8290 can be configured to operate in dual-supply mode.
An example of such a circuit is shown in Figure 46, where the
AD8290 is p
dual supplies, pins that are normally referenced to ground in the
single-supply mode, now need to be referenced to the negative
supply. These pins include the following: Pin 1, Pin 7, Pin 8, Pin 9,
Pin 10, Pin 12, and Pin 16. External components, such as R
sensing bridge, and the antialiasing filter capacitor at the output,
should also be referenced to the negative supply. Additionally,
two bypass capacitors should be added beyond what is necessary
for single-supply operation: one between the negative supply
and ground, and the other between the positive and negative
supplies.

When operating in dual-supply mode, the specifications change

nd become relative to the negative supply. The input voltage

a
range minimum shifts from 0.2 V to 0.2 V above the negative
supply (in this example: −1.6 V), the output voltage range shifts
from a minimum of 0.075 V to 0.075 V above the negative supply
(in this example: −1.725 V), and the excitation current pin
voltage minimum shifts from 0 V to −1.8 V in this example.
The maximum specifications of these three parameters are
specified relative to V

For other specifications, both the minimum and maximum

ecifications change. The output offset shifts from a minimum

sp
of +865 mV and maximum of +935 mV to a minimum of

−935 mV and a maximum of −865 mV in the example. In
addition, the logic levels for the ENBL operation should be
adjusted accordingly.

C

FILTER

6.8nF

56

CF2CF1

AD8290

owered by ±1.8 V supplies. When operating with

in Tabl e 1 and do not change.

CC

1.8V

C1

0.1µF

C3

0.1µF

C5

0.1µF

–1.8V

3

ENBL

VCC

GND

2

10

SET

, the

15

VINP

C

BRIDGE

NC = NO CONNECT
NOTES

LAYOUT CONSIDERATIONS:

1. KEEP C1 CLO SE TO PIN 2 AND PIN 10.

2. KEEP C3 CLO SE TO PIN 2.

3. KEEP C5 CLO SE TO PIN 10.

4. KEEP R

–1.8V

CLOSE TO PIN 11.

SET

Figure 46. Typical Dual-Supply C

NC NCNCNC NC NC

8

7

–1.8V

onnections

VOUT

161 129

4

Rev. B | Page 17 of 20

C2
68nF

V

OUT

6745-029

AD8290

www.BDTIC.com/ADI

PRESSURE SENSOR BRIDGE APPLICATION

Given its excitation current range, the AD8290 provides a good
match with pressure sensor circuits. Two such sensors are the
Fujikura FGN-615PGSR and the Honeywell HPX050AS. Figure 47
s

hows the AD8290 paired with the Honeywell bridge and the
appropriate connections. In this example, a resistor, R
to the circuit to ensure that the maximum output voltage of the
AD8290 is not exceeded. Depending on the sensors specifications,
R

may not be necessary.

P

R

C

P

BRIDGE

2kΩ

0.1µF

HPX050AS

2

P

8

4

5

, is added

R

SET

2.7kΩ

6

The specifications for the bridge are show in Table 5 and the
c

hosen conditions for the AD8290 are listed in Tabl e 6.

Given these specifications, calculations should be made to ensure
t

hat the AD8290 is operating within its required ranges. The

combination of the excitation current and R

must be chosen

P

to ensure that the conditions stay within the minimum and
maximum specifications of the AD8290. For this example,
because the specifications of the HPX050AS are for a bridge
excitation voltage of 3.0 V, care must be taken to scale the
resulting voltage calculations to the actual bridge voltage. The
required calculations are shown in

C

FILTER

6.8nF

11

RSET

IOUT

13

14

VINN

15

VINP

NC NC

6

AD8290

NC NC NC

7

5

CF2CF1

NC

8

129

3

ENBL

GND

VOUT

VCC

161

2

10

4

C1

0.1µF

C2
68nF

3.3V

Tabl e 7.

NC = NO CONNECT

Figure 47. HPX050AS Pressure Sensor Application

06745-030

Table 5. HPX050AS Specifications

Bridge Impedance (Ω) Rated Offset (mV) Rated Output Span (mV)

Minimum Maximum Minimum Maximum Minimum Maximum Bridge Excite Voltage (V)

4000 6000 −30 +30 0 80 3.0

Table 6. Typical AD8290 Conditions for Pressure Sensor Circuit

AD8290 VCC (V) Excitation Current (μA) Parallel Resistor RP (Ω)

3.3 (2.6 to 5.5) 333.3 (300 to 1300) 2000

Table 7. Pressure Sensor Circuit Calculations Compared to AD8290 Minimum/Maximum Specifications

Specification Calculation Unit Allowable Range of AD8290

Supply Current 1.867 mA
Current Setting Resistor (R
Minimum Equivalent Resistance to IOUT Pin 1333 Ω
Maximum Equivalent Resistance to IOUT Pin 1500 Ω
Minimum Current into Bridge 83.333 μA
Maximum Current into Bridge 111.111 μA
Minimum Bridge Midpoint Voltage (Excluding Offset/Span) 0.222 V
Maximum Bridge Midpoint Voltage (Ex
Minimum Voltage at Current Output Pin (IOUT) 0.444 V
Maximum Voltage at Current Output Pin (IOUT) 0.500 V
Input Voltage Minimum 0.218 V
Input Voltage Maximum 0.266 V
Output Voltage Minimum 0.643 V

) 2700 Ω 692 Ω to 3000 Ω

SET

cluding Offset/Span) 0.250 V

>0.0 V
<2.3 V
>0.2 V
<1.6 V
>0.075 V

Output Voltage Maximum 1.852 V <3.225 V

Rev. B | Page 18 of 20

AD8290

www.BDTIC.com/ADI

TEMPERATURE SENSOR APPLICATION

The AD8290 can be used with a temperature sensor. Figure 48
shows the AD8290 in conjunction with an RTD, in this
example, a 2-wire PT100. The specifications for the sensor are
shown in
lis

Once again, care must be taken when picking the excitation
cu
specifications of the AD8290 are not exceeded. Sample
calculations are shown in

Tabl e 8 and the chosen conditions for the AD8290 are

ted in Table 9 .

rrent and R

such that the minimum and maximum

G

Table 10.

C

BRIDGE

0.1µF

R

3kΩ

SET

RTD

R

G

698Ω

11

RSET

13

IOUT

15

VINP

14

VINN

NC NC

NC NC NC

7

ADC/MICROCONTROLLER

In both of the previous applications, an ADC or a microcontroller
can be used to follow the AD8290 to convert the output analog
signal to digital. For example, if there are multiple sensors in the
system, the six channel ADuC814ARU microcontoller is an
excellent candidate to interface with multiple AD8290s.

C

FILTER

6.8nF

AD8290

8

NC

3

56

ENBL

CF2CF1

VCC

GND

VOUT

161

129

3.3V

2

C1

0.1µF

10

4

C2
68nF

NC = NO CONNECT

Figure 48. PT100 Temperature Sensor

Application Connections

06745-044

Table 8. PT100 Specifications

RTD Minimum @ 0°C RTD Maximum @ 100°C

100 Ω 138.5 Ω

Table 9. Typical AD8290 Conditions for Temperature Sensor Circuit

AD8290 VCC (V) Excitation Current (μA) Resistor from RTD to GND, RG (Ω)

3.30 (2.6 to 5.5) 300 (300 to 1300) 698

Table 10. Temperature Sensor Circuit Calculations Compared to AD8290 Minimum/Maximum Specifications

Specification Calculation Unit Allowable Range of AD8290

Supply Current 1.8 mA
Current Setting Resistor (R
Minimum Equivalent Resistance to IOUT Pin 798 Ω
Maximum Equivalent Resistance to IOUT Pin 836.5 Ω
Minimum Voltage @ Current Output Pin (IOUT) 0.239 V
Maximum Voltage @ Current Output Pin (IOUT) 0.251 V
Input Voltage Minimum 0.209 V
Input Voltage Maximum 0.251 V
Output Voltage Minimum 2.365 V

) 3000 Ω 692 Ω to 3000 Ω

SET

>0.0 V
<2.3 V
>0.2 V
<1.6 V
>0.075 V

Output Voltage Maximum 3.013 V <3.225 V

Rev. B | Page 19 of 20

AD8290

www.BDTIC.com/ADI

OUTLINE DIMENSIONS

INDEX

AREA

0.60

0.55

0.51

SEATING

PLANE

3.00

BSC SQ

13

EXPOSED

PAD

8

16

12

0.50

TOP VIEW BOTTOM VIEW

0.30

0.25

0.18

BSC

0.05 MAX

0.02 NOM

0.08 REF

9

N

1

P

I

R

O

D

C

I

A

T

N

I

1

1.80

1.70 SQ

1.55

4

5

0.40 MAX

0.30 NOM

COMPLIANTTOJEDEC STANDARDS MO-248-UEED.

053106-B

Figure 49. 16-Lead Lead Frame Chip Scale Package [LFCSP_UQ]

× 3 mm Body, Ultra Thin Quad

3 mm

(CP-16-12)

Dimensions shown in millimeters

ORDERING GUIDE

Model Temperature Range Package Description Package Option Branding

AD8290ACPZ-R2
AD8290ACPZ-R7
AD8290ACPZ-RL

1

Z = RoHS Compliant Part.

1

1

1

−40°C to +85°C 16-Lead LFCSP_UQ CP-16-12 Y0J

−40°C to +85°C 16-Lead LFCSP_UQ CP-16-12 Y0J

−40°C to +85°C 16-Lead LFCSP_UQ CP-16-12 Y0J

©2007–2008 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D06745-0-2/08(B)

Rev. B | Page 20 of 20