ANALOG DEVICES AD8290 Service Manual

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
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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

www.BDTIC.com/ADI

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