Datasheet

ManualsBrandsANALOG DEVICES ManualsLinear ICsLinear IC - Op-amp Current sensor LFCSP 16 UQ (3x3)

G = 50, CMOS Sensor Amplifier

with Current Excitation

AD8290

Rev. B

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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

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,

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

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 package and is operational over the industrial

temperature range of −40°C to +85°C.

FUNCTIONAL BLOCK DIAGRAM

REF

11 6 5 3

ADC

ANTI-

ALIASING

FILTER

GND

ENBL

FILTER

SET

06745-001

AD8290

BRIDGE

NC NCNCNC NC NC

161 1297 8

Figure 1.

Summary of content (20 pages)

PAGE 1
G = 50, CMOS Sensor Amplifier with Current Excitation AD8290 FEATURES GENERAL DESCRIPTION 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 The AD8290 contains both an adjustable current source to drive a sensor and a difference amplifier to amplify the signal voltage.
PAGE 2
AD8290 TABLE OF CONTENTS Features .............................................................................................. 1 Current Source............................................................................ 15 Applications....................................................................................... 1 Applications Information .............................................................. 16 General Description ......................................................................
PAGE 3
AD8290 SPECIFICATIONS VCC = 2.6 V to 5.0 V, TA = 25°C, CFILTER = 6.8 nF, output antialiasing capacitor = 68 nF, RSET = 3 kΩ, common-mode input = 0.6 V, unless otherwise noted. Table 1.
PAGE 4
AD8290 Parameter POWER SUPPLY Operating Range Quiescent Current Test Conditions Min Typ Max Unit 1.2 + 2× excitation current 0.5 5.5 1.8 + 2× excitation current 10 V mA +85 °C 2.6 Shutdown Current TEMPERATURE RANGE For Operational Performance −40 Rev.
PAGE 5
AD8290 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Supply Voltage Input Voltage Differential Input Voltage 1 Output Short-Circuit Duration to GND Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature (Soldering, 10 sec) 1 Rating 6V +VSUPPLY ±VSUPPLY Indefinite −65°C to +150°C −40°C to +85°C −65°C to +150°C 300°C Differential input voltage is limited to ±5.0 V, the supply voltage, or whichever is less.
PAGE 6
AD8290 9 NC NC 8 NC 7 11 RSET 10 GND (Not to Scale) CF2 5 12 NC NC = NO CONNECT 06745-002 14 VINN TOP VIEW ENBL 3 VOUT 4 13 IOUT 16 NC AD8290 CF1 6 NC 1 VCC 2 15 VINP PIN CONFIGURATION AND FUNCTION DESCRIPTIONS Figure 2. Pin Configuration Table 4. Pin Function Descriptions Pin No. 1 2 3 4 Mnemonic NC VCC ENBL VOUT 5 6 7 8 9 10 11 12 13 14 15 16 17/Pad CF2 CF1 NC NC NC GND RSET NC IOUT VINN VINP NC NC 1 Description Tie to Ground 1 or Pin 16. Positive Power Supply Voltage.
PAGE 7
AD8290 TYPICAL PERFORMANCE CHARACTERISTICS 25 35 30 20 UNITS (%) UNITS (%) 25 20 15 15 10 10 5 892 894 896 898 900 902 904 906 908 OUTPUT VOLTAGE (mV) 0 06745-003 0 Figure 3. Output Offset Voltage at 2.6 V Supply 0.2988 0.2991 0.2994 0.3000 0.3006 0.3012 0.2997 0.3003 0.3009 EXCITATION CURRENT (mA) 06745-006 5 Figure 6. Excitation Output Current for 3 kΩ RSET at 2.
PAGE 8
25 25 20 20 15 15 UNITS (%) 10 5 1.296 1.297 1.298 1.299 1.300 1.301 1.302 1.303 1.304 1.305 EXCITATION CURRENT (mA) 0 GAIN ERROR (%) Figure 12. Percent Gain Error at 2.6 V Supply 25 25 20 20 15 15 UNITS (%) 10 10 5 5 EXCITATION CURRENT (mA) 0 06745-010 1.296 1.297 1.298 1.299 1.300 1.301 1.302 1.303 1.304 1.305 GAIN ERROR (%) Figure 13. Percent Gain Error at 3.6 V Supply 25 25 20 20 15 15 UNITS (%) UNITS (%) Figure 10. Output Excitation Current for 692 Ω RSET at 3.
PAGE 9
AD8290 50 40 35 40 25 UNITS (%) UNITS (%) 30 20 15 30 20 10 10 0.0030 0.0035 0.0040 0.0050 0.0060 0.0070 0.0045 0.0055 0.0065 NONLINEARITY (%) 0 06745-026 0 –35 –15 5 25 45 65 85 105 125 DRIFT (µV/°C) 06745-031 5 Figure 18. Output Offset Voltage Drift from −40°C to +85°C at 2.6 V Supply Figure 15. Percent Nonlinearity at 2.6 V Supply 50 35 30 40 UNITS (%) UNITS (%) 25 20 15 30 20 10 10 0.0030 0.0035 0.0040 0.0050 0.0060 0.0070 0.0045 0.0055 0.
PAGE 10
AD8290 45 40 40 35 35 30 25 UNITS (%) 25 20 15 20 35 50 65 80 95 110 125 DRIFT (ppm/°C) 0 06745-035 5 40 40 35 35 40 50 60 70 80 90 30 30 25 UNITS (%) 25 20 15 20 15 10 10 5 5 20 35 50 65 80 95 110 125 DRIFT (ppm/°C) 0 06745-036 5 10 20 30 40 50 60 70 80 90 DRIFT (ppm/°C) Figure 22. Excitation Current Drift from −40°C to +85°C at 3.6 V Supply, RSET = 3 kΩ 06745-040 UNITS (%) 30 Figure 24. Excitation Current Drift from −40°C to +85°C at 2.
PAGE 11
AD8290 100 40 35 30 GAIN (V/V) UNITS (%) 25 20 15 10 10 –16.0 –15.5 –15.0 –14.5 –14.0 –13.5 –13.0 –12.5 –12.0 DRIFT (ppm/°C) 1 06745-045 0 1 10 100 1k 10k FREQUENCY (Hz) Figure 27. Gain Drift from −40°C to +85°C at 2.6 V Supply 06745-018 5 Figure 30. Frequency Response for Supply Range of 2.6 V to 5.0 V (External CFILTER = 6.8 nF, Antialiasing Capacitor = 68 nF) 310 40 308 35 EXCITATION CURRENT (µA) 306 30 20 15 10 5 302 300 298 296 294 –16.0 –15.5 –15.0 –14.5 –14.0 –13.5 –13.
PAGE 12
AD8290 50.0 310 49.9 300 2.6V SUPPLY 3.6V SUPPLY 2.6V SUPPLY 49.8 5V SUPPLY 49.7 3.6V SUPPLY 290 5.0V SUPPLY 49.6 285 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 PIN VOLTAGE (V) 49.5 –55 –45 –35 –25 –15 –5 06745-021 280 5 15 25 35 45 55 65 75 85 95 TEMPERATURE (°C) Figure 33. Low Excitation Current vs. Excitation Current Pin Voltage 06745-052 295 GAIN (V/V) EXCITATION CURRENT (µA) 305 Figure 36. Gain vs. Temperature 1.32 0.305 0.
PAGE 13
AD8290 1000 1.5 1.3 1.2 5.0V SUPPLY 3.6V SUPPLY NOISE (nV Hz) QUIESCENT CURRENT (mA) 1.4 1.1 1.0 0.9 2.6V SUPPLY 100 10 0.8 5 15 25 35 45 55 65 75 TEMPERATURE (°C) 85 95 1 0.01 06745-043 0.6 –45 –35 –25 –15 –5 0.1 1 10 100 1000 FREQUENCY (Hz) Figure 39. Quiescent Current vs. Temperature (Excludes 2× Excitation Current) 06745-051 0.7 Figure 41. Input-Referred Noise vs. Frequency 1.0 INPUT-REFERRED NOISE (100nV/DIV) 0.9 0.
PAGE 14
AD8290 THEORY OF OPERATION AMPLIFIER HIGH POWER SUPPLY REJECTION (PSR) AND COMMON-MODE REJECTION (CMR) 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. 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.
PAGE 15
AD8290 CURRENT SOURCE The AD8290 generates an excitation current that is programmable with an external resistor, RSET, as shown in Figure 44. A1 and M1 are configured to produce 0.9 V across RSET, which is based on an internal 0.9 V reference and creates a current equal to 0.9 V/RSET internal to the AD8290. This current 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.
PAGE 16
AD8290 APPLICATIONS INFORMATION For bandwidths greater than 10 Hz, an additional single-pole RC 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 Figure 43) and using an external 68 nF capacitor to ground produces an RC filter of 235 Hz on the output as well. These two filters produce an overall bandwidth of approximately 160 Hz for the output signal.
PAGE 17
AD8290 DUAL-SUPPLY OPERATION MAXIMIZING PERFORMANCE THROUGH PROPER LAYOUT 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 powered by ±1.8 V supplies. When operating with 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.
PAGE 18
AD8290 The specifications for the bridge are show in Table 5 and the chosen conditions for the AD8290 are listed in Table 6. 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 shows the AD8290 paired with the Honeywell bridge and the appropriate connections.
PAGE 19
AD8290 TEMPERATURE SENSOR APPLICATION ADC/MICROCONTROLLER 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 Table 8 and the chosen conditions for the AD8290 are listed in Table 9. 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.
PAGE 20
AD8290 OUTLINE DIMENSIONS 3.00 BSC SQ PIN 1 INDICATOR 13 12 16 1 1.80 1.70 SQ 1.55 EXPOSED PAD 0.50 BSC TOP VIEW 0.60 0.55 0.51 SEATING PLANE 9 8 5 4 BOTTOM VIEW 0.40 MAX 0.30 NOM 0.05 MAX 0.02 NOM 0.30 0.25 0.18 0.08 REF 053106-B INDEX AREA COMPLIANT TO JEDEC STANDARDS MO-248-UEED. Figure 49.