Datasheet

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Low Gain Drift

Precision Instrumentation Amplifier

AD8228

Rev. 0

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FEATURES

Easy to use

Pin strappable gains of 10 and 100

Wide power supply range: ±2.3 V to ±18 V

DC specifications (B Grade, G = 10)

2 ppm/°C gain drift

0.02% gain error

50 μV maximum input offset voltage

0.8 μV/°C maximum input offset drift

0.6 nA maximum input bias current

100 dB CMRR

AC specifications

650 kHz, –3 dB bandwidth (G = 10)

2 V/μs slew rate

Low noise

8 nV/√Hz, @ 1 kHz (G = 100)

0.3 μV p-p from 0.1 Hz to 10 Hz (G = 100)

APPLICATIONS

Weigh scales

Industrial process controls

Bridge amplifiers

Precision data acquisition systems

Medical instrumentation

Strain gages

Transducer interfaces

GENERAL DESCRIPTION

The AD8228 is a high performance instrumentation amplifier

with very high gain accuracy. Because all gain setting resistors

are internal and laser trimmed, gain accuracy and gain drift

are better than can be achieved with typical instrumentation

amplifiers.

Low voltage offset, low offset drift, low gain drift, high gain

accuracy, and high CMRR make this part an excellent choice

in applications that demand the best dc performance possible,

such as bridge signal conditioning.

CONNECTION DIAGRAM

–IN

OUT

REF

–V

TOP VIEW

(Not to Scale)

AD8228

07035-001

Figure 1.

Table 1. Instrumentation Amplifiers by Category

General

Purpose

Zero

Drift

Military

Grade

Low

Power

High Speed

PGA

AD8220

AD8231

AD620 AD627

AD8250

AD8221 AD8553

AD621 AD623

AD8251

AD8222 AD8555

AD524 AD8253

AD8224

AD8556

AD526

AD8228 AD8557

AD624

Rail-to-rail output.

The AD8228 operates on both single and dual supplies. Because

the part can operate on supplies up to ±18 V, it is well suited for

applications where high common-mode input voltages are

encountered. The AD8228 is available in 8-lead MSOP and

SOIC packages.

Performance is specified over the entire industrial temperature

range of −40°C to +85°C for all grades. Furthermore, the AD8228

is operational from −40°C to +125°C. For a pin-compatible ampli-

fier with similar specifications, but with a gain range of 1 to 1000,

see the

AD8221.

Summary of content (24 pages)

PAGE 1
Low Gain Drift Precision Instrumentation Amplifier AD8228 CONNECTION DIAGRAM Easy to use Pin strappable gains of 10 and 100 Wide power supply range: ±2.3 V to ±18 V DC specifications (B Grade, G = 10) 2 ppm/°C gain drift 0.02% gain error 50 μV maximum input offset voltage 0.8 μV/°C maximum input offset drift 0.6 nA maximum input bias current 100 dB CMRR AC specifications 650 kHz, –3 dB bandwidth (G = 10) 2 V/μs slew rate Low noise 8 nV/√Hz, @ 1 kHz (G = 100) 0.3 μV p-p from 0.
PAGE 2
AD8228 TABLE OF CONTENTS Features .............................................................................................. 1 Architecture ................................................................................ 16 Applications....................................................................................... 1 Setting the Gain .......................................................................... 16 General Description ...............................................................
PAGE 3
AD8228 SPECIFICATIONS GAIN = 10 VS = ±15 V, VREF = 0 V, TA = 25°C, RL = 2 kΩ, all specifications referred to input, unless otherwise noted. Table 2. Parameter COMMON-MODE REJECTION RATIO CMRR DC to 60 Hz with 1 kΩ Source Imbalance CMRR at 2 kHz NOISE Voltage Noise Current Noise VOLTAGE OFFSET Offset Over Temperature Average TC Offset vs.
PAGE 4
AD8228 Parameter OUTPUT Output Swing Over Temperature Output Swing Over Temperature Short-Circuit Current POWER SUPPLY Operating Range Quiescent Current Over Temperature TEMPERATURE RANGE Specified Performance Operating Range 2 Conditions (Gain = 10) RL = 10 kΩ VS = ±2.3 V to ±5 V T = −40°C to +85°C VS = ±5 V to ±18 V T = –40°C to +85°C Min A Grade Typ −VS + 1.1 −VS + 1.4 −VS + 1.2 −VS + 1.6 Max Min +VS − 1.2 +Vs − 1.3 +VS − 1.4 +VS − 1.5 −VS + 1.1 −VS + 1.4 −VS + 1.2 −VS + 1.6 18 VS = ±2.
PAGE 5
AD8228 GAIN = 100 VS = ±15 V, VREF = 0 V, TA = 25°C, RL = 2 kΩ, all specifications referred to input, unless otherwise noted. Table 3. Parameter COMMON-MODE REJECTION RATIO CMRR DC to 60 Hz with 1 kΩ Source Imbalance CMRR at 2 kHz NOISE Voltage Noise Current Noise VOLTAGE OFFSET Offset Over Temperature Average TC Offset vs.
PAGE 6
AD8228 Parameter OUTPUT Output Swing Over Temperature Output Swing Over Temperature Short-Circuit Current POWER SUPPLY Operating Range Quiescent Current Over Temperature TEMPERATURE RANGE Specified Performance Operating Range 2 Conditions (Gain = 100) RL = 10 kΩ VS = ±2.3 V to ±5 V T = −40°C to +85°C VS = ±5 V to ±18 V T = −40°C to +85°C Min A Grade Typ −VS + 1.1 −VS + 1.4 −VS + 1.2 −VS + 1.6 Max Min +VS − 1.2 +Vs − 1.3 +VS − 1.4 +VS − 1.5 −VS + 1.1 −VS + 1.4 −VS + 1.2 −VS + 1.6 18 VS = ±2.
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AD8228 ABSOLUTE MAXIMUM RATINGS Table 4. Parameter Supply Voltage Output Short-Circuit Current Input Voltage (Common Mode) Differential Input Voltage Storage Temperature Range Operating Temperature Range1 Maximum Junction Temperature ESD Human Body Model Charge Device Model 1 THERMAL RESISTANCE Rating ±18 V Indefinite ±VS ±VS −65°C to +150°C −40°C to +125°C 140°C θJA is specified for a device in free air. Table 5.
PAGE 8
AD8228 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS –IN 1 8 +VS G1 2 7 VOUT G2 3 6 REF AD8228 5 –VS TOP VIEW (Not to Scale) 07035-004 +IN 4 Figure 2. Pin Configuration Table 6. Pin Function Descriptions Pin No. 1 2, 3 4 5 6 7 8 Mnemonic −IN G1, G2 +IN −VS REF VOUT +VS Description Negative Input. Gain Pins. Short together for a gain of 100. Leave unconnected for a gain of 10. Positive Input. Negative Supply. Reference. Output. Positive Supply. Rev.
PAGE 9
AD8228 TYPICAL PERFORMANCE CHARACTERISTICS T = 25°C, VS = ±15 V, RL = 10 kΩ, unless otherwise noted. MEAN: –5.5 SD: 12.4 70 MEAN: 0.20 SD: 0.12 100 60 80 HITS HITS 50 40 30 60 40 20 20 –100 –50 0 50 G10 SYSTEM VOS RTI @ 15V (µV) 100 0 07035-043 0 Figure 3. Typical Distribution of Input Offset Voltage (G = 10) 1.5 100 MEAN: 0.29 SD: 0.27 80 50 40 60 HITS HITS –0.5 0 0.5 1.0 G100 SYSTEM VOS DRIFT RTI (µV) Figure 6.
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AD8228 5 INPUT COMMON-MODE VOLTAGE (V) 4 80 HITS 60 40 0 –0.6 –0.4 –0.2 0 0.2 IOS @ 15V (nA) 0.4 0.6 07035-050 20 VS = ±5V 3 2 1 0 VS = ±2.5V –1 –2 –3 –4 –5 –5 –4 –3 –2 –1 0 1 2 OUTPUT VOLTAGE (V) 3 4 5 07035-035 MEAN: –0.097 SD: 0.07 Figure 12. Input Common-Mode Voltage vs. Output Voltage, VS = ±2.5 V, ±5 V; G = 100 Figure 9. Typical Distribution of Input Offset Current 5 15 2 1 0 VS = ±2.
PAGE 11
2.00 160 1.75 140 NEGATIVE PSRR (dB) 1.50 1.25 1.00 0.75 0.50 G = 100 120 G = 10 100 80 60 0 0.01 0.1 1 WARM-UP TIME (Minutes) 10 20 0.1 Figure 15. Change in Input Offset Voltage vs. Warm-Up Time 1 10 100 1k FREQUENCY (Hz) 10k 100k 1M 07035-013 40 0.25 07035-002 CHANGE IN INPUT OFFSET VOLTAGE (µV) AD8228 Figure 18. Negative PSRR vs.
PAGE 12
AD8228 140 +VS – 0 G = 100 INPUT VOLTAGE LIMIT (V) REFERRED TO SUPPLY VOLTAGES +VS – 0.4 120 CMRR (dB) G = 10 100 80 60 +VS – 0.8 +VS – 1.2 +VS – 1.6 +VS – 2.0 –VS + 2.0 –VS + 1.6 –VS + 1.2 –VS + 0.8 1 10 100 1k FREQUENCY (Hz) 10k 100k 1M –VS + 0 07035-039 0 5 10 SUPPLY VOLTAGE (±V) 15 20 Figure 24. Input Voltage Limit vs. Supply Voltage Figure 21. CMRR vs. Frequency, RTI 140 +VS – 0 +VS – 0.
PAGE 13
AD8228 1k +VS –0 VOLTAGE NOISE RTI (nV/√Hz) OUTPUT VOLTAGE SWING (V) REFERRED TO SUPPLY VOLTAGE –1 –2 –3 +3 +2 100 G = 10 10 G = 100 0 1 2 3 4 5 6 7 8 OUTPUT CURRENT (mA) 9 10 11 12 1 07035-021 –VS +0 1 100 1k FREQUENCY (Hz) 10k 100k Figure 30. Voltage Noise Spectral Density vs. Frequency –10 –8 –6 –4 –2 0 2 4 OUTPUT VOLTAGE (V) 6 8 10 1s/DIV 07035-016 0.2µV/DIV 07035-023 ERROR (10ppm/DIV) Figure 27. Output Voltage Swing vs.
PAGE 14
AD8228 5pA/DIV 5V/DIV 20µs/DIV Figure 33. 0.1 Hz to 10 Hz Current Noise 07035-026 1s/DIV 07035-031 0.002%/DIV Figure 36. Large Signal Pulse Response and Settling Time (G = 100) 30 VS = ±15V 20 15 G = 10, 100 20mV/DIV 10 5 10k 100k FREQUENCY (Hz) 1M 07035-024 4µs/DIV 0 1k 07035-027 OUTPUT VOLTAGE (V p-p) 25 Figure 34. Large Signal Frequency Response Figure 37. Small Signal Response, G = 10, RL = 2 kΩ, CL = 100 pF 5V/DIV 07035-025 20µs/DIV 4µs/DIV Figure 35.
PAGE 15
AD8228 15 20.0 G = 10 RL = 10kΩ G = 100 RL = 10kΩ SETTLING TIME (µs) 0.001% SETTLING TIME 0.01% SETTLING TIME 5 0.001% SETTLING TIME 15.0 12.5 0 0 5 10 15 OUTPUT VOLTAGE STEP SIZE (V p-p) 20 10.0 Figure 39. Settling Time vs. Step Size, G = 10 0 5 10 15 OUTPUT VOLTAGE STEP SIZE (V p-p) Figure 40. Settling Time vs. Step Size, G = 100 Rev. 0 | Page 15 of 24 20 07035-042 0.01% SETTLING TIME 07035-041 SETTLING TIME (µs) 17.
PAGE 16
AD8228 THEORY OF OPERATION I I VBIAS IB COMPENSATION A1 IB COMPENSATION A2 C1 10kΩ C2 +VS 10kΩ R1 22kΩ –IN 600Ω Q1 R2 22kΩ +VS V1 –VS +VS R3 4.889kΩ +VS Q2 –VS 10kΩ 600Ω REF +IN V2 –VS –VS G1 G2 –VS +VS 07035-018 +VS OUTPUT A3 10kΩ GAIN R4 –VS SET 489Ω Figure 41. Simplified Schematic ARCHITECTURE SETTING THE GAIN The AD8228 is based on the classic three op amp topology.
PAGE 17
AD8228 REFERENCE TERMINAL Common-Mode Rejection Ratio over Frequency The output voltage of the AD8228 is developed with respect to the potential on the reference terminal. This is useful when the output signal needs to be offset to a precise midsupply level. For example, a voltage source can be tied to the REF pin to level-shift the output so that the AD8228 can drive a single-supply ADC. The REF pin is protected with ESD diodes and should not exceed either +VS or −VS by more than 0.3 V.
PAGE 18
AD8228 References The output voltage of the AD8228 is developed with respect to the potential on the reference terminal. Care should be taken to tie REF to the appropriate local ground. For applications where the AD8228 encounters extreme overload voltages, such as cardiac defibrillators, external series resistors and low leakage diode clamps such as the BAV199L, the FJH1100s, or the SP720 should be used.
PAGE 19
AD8228 APPLICATIONS INFORMATION DIFFERENTIAL DRIVE PRECISION STRAIN GAGE Figure 48 shows how to configure the AD8228 for differential output. The advantage of this circuit is that the dc differential accuracy depends on the AD8228 and not on the op amp or the resistors. This circuit takes advantage of the precise control the AD8228 has of its output voltage relative to the reference voltage.
PAGE 20
AD8228 OUTLINE DIMENSIONS 3.20 3.00 2.80 8 3.20 3.00 2.80 5.15 4.90 4.65 5 1 4 PIN 1 0.65 BSC 0.95 0.85 0.75 1.10 MAX 0.15 0.00 0.38 0.22 COPLANARITY 0.10 0.80 0.60 0.40 8° 0° 0.23 0.08 SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 51. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters 5.00 (0.1968) 4.80 (0.1890) 8 1 5 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE 6.20 (0.2441) 5.80 (0.2284) 1.75 (0.0688) 1.
PAGE 21
AD8228 ORDERING GUIDE Model AD8228ARMZ 1 AD8228ARMZ-RL1 AD8228ARMZ-R71 AD8228ARZ1 AD8228ARZ-RL1 AD8228ARZ-R71 AD8228BRMZ1 AD8228BRMZ-RL1 AD8228BRMZ-R71 AD8228BRZ1 AD8228BRZ-RL1 AD8228ARZ-R71 1 Temperature Range –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C Package Description 8-Lead MSOP 8-Lead MSOP, 13" Tape and Reel 8-Lead MSOP, 7" Tape and Reel 8-Lead SOIC_N 8-Lead SOIC_
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AD8228 NOTES Rev.
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AD8228 NOTES Rev.