AD8270 Analog Devices, AD8270 Datasheet

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AD8270

Manufacturer Part Number
AD8270
Description
Precision Dual-Channel, Difference Amplifier
Manufacturer
Analog Devices
Datasheet

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FEATURES
With no external resistors
Excellent ac specifications
High accuracy dc performance
Two channels in small 4 mm × 4 mm LFCSP
Supply current: 2.5 mA per channel
Supply range: ±2.5 V to ±18 V
APPLICATIONS
Instrumentation amplifier building blocks
Level translators
Automatic test equipment
High performance audio
Sine/Cosine encoders
GENERAL DESCRIPTION
The AD8270 is a low distortion, dual-channel amplifier with
internal gain setting resistors. With no external components,
it can be configured as a high performance difference amplifier
with gains of 0.5, 1, or 2. It can also be configured in over 40 single-
ended configurations, with gains ranging from −2 to +3.
The AD8270 is the first dual-difference amplifier in the small
4 mm × 4 mm LFCSP. It requires the same board area as a typical
single-difference amplifier. The smaller package allows a 2×
increase in channel density and a lower cost per channel, all
with no compromise in performance.
The AD8270 operates on both single and dual supplies and
requires only 2.5 mA maximum supply current for each ampli-
fier. It is specified over the industrial temperature range of
−40°C to +85°C and is fully RoHS compliant.
Rev. 0
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.
Difference amplifier: gains of 0.5, 1, or 2
Single ended amplifiers: over 40 different gains
Set reference voltage at midsupply
15 MHz bandwidth
30 V/μs slew rate
0.08% maximum gain error
10 ppm/°C maximum gain drift
80 dB minimum CMRR (G = 2)
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
Table 1. Difference Amplifiers by Category
High
Speed
AD8270
AD8273
AMP03
–IN1A
–IN2A
+IN2A
+IN1A
1
2
3
4
Precision Dual-Channel,
FUNCTIONAL BLOCK DIAGRAM
10kΩ
10kΩ
10kΩ
10kΩ
High
Voltage
AD628
AD629
20kΩ
_
+
Difference Amplifier
10kΩ
20kΩ
©2008 Analog Devices, Inc. All rights reserved.
AD8270
Single-Supply
Unidirectional
AD8202
AD8203
Figure 1.
20kΩ
10kΩ
20kΩ
_
+
10kΩ
10kΩ
10kΩ
10kΩ
AD8270
Single-Supply
Bidirectional
AD8205
AD8206
AD8216
www.analog.com
12 –IN1B
11 –IN2B
10 +IN2B
9 +IN1B

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AD8270 Summary of contents

Page 1

... It can also be configured in over 40 single- ended configurations, with gains ranging from −2 to +3. The AD8270 is the first dual-difference amplifier in the small 4 mm × LFCSP. It requires the same board area as a typical single-difference amplifier. The smaller package allows a 2× ...

Page 2

... Maximum Power Dissipation ..................................................... 5 ESD Caution.................................................................................. 5 Pin Configuration and Function Descriptions............................. 6 Typical Performance Characteristics ............................................. 7 Theory of Operation ...................................................................... 13 REVISION HISTORY 1/08—Revision 0: Initial Version Circuit Information.................................................................... 13 Driving the AD8270................................................................... 13 Package Considerations............................................................. 13 Power Supplies............................................................................ 13 Input Voltage Range................................................................... 14 Applications Information .............................................................. 15 Difference Amplifier Configurations ...................................... 15 Single-Ended Configurations ................................................... 15 Differential Output .................................................................... 17 Driving an ADC ...

Page 3

... AD8270 Unit MHz V/μ μV p-p nV/√Hz % ppm/°C μV μV/°C dB μV/V V kΩ ...

Page 4

... AD8270 V = ± 25° REF A LOAD Table 3. Parameter DYNAMIC PERFORMANCE Bandwidth Slew Rate Settling Time to 0.01% Settling Time to 0.001% NOISE/DISTORTION Harmonic Distortion 1 Voltage Noise GAIN Gain Error Gain Drift INPUT CHARACTERISTICS 2 Offset Average Temperature Drift Common-Mode Rejection Ratio Power Supply Rejection Ratio ...

Page 5

... MAXIMUM POWER DISSIPATION Rating The maximum safe power dissipation for the AD8270 is limited ± the associated rise in junction temperature (T See derating approximately 130°C, which is the glass transition temperature, curve in Figure 2 the plastic changes its properties ...

Page 6

... Resistor Connected to Negative Terminal of Op Amp B. 13 −V Negative Supply OUTB Op Amp B Output. 15 OUTA Op Amp A Output Positive Supply. S PIN 1 INDICATOR 12 –IN1B –IN1A 1 AD8270 11 –IN2B –IN2A 2 TOP VIEW +IN2A 3 10 +IN2B (Not to Scale) +IN1A 4 9 +IN1B Figure 3. Pin Configuration Rev Page ...

Page 7

... Figure 8. Common-Mode Input Voltage vs. Output Voltage, Gain = 0.5, ±5 V and ±2.5 V Supplies 20 (0, +15) 15 (–14.3, +7.85 –5 –10 (–14.3, –7.85) –15 (0, –15) –20 –20 –15 –10 – OUTPUT VOLTAGE (V) Figure 9. Common-Mode Input Voltage vs. Output Voltage, Gain = 1, ±15 V Supplies AD8270 (+7.5, +7.5) (+7.5, –7.5) 10 (+2.5, +2.5) = ±5 S (+2.5, –2. (+14.3, +7.85) (+14.3, –7.85 ...

Page 8

... AD8270 6 (0, +5) 4 (–4.3, +2.85) (0, +2.5) 2 (–1.6, +1. ±2 (–1.6, –1.7) –2 (0, –2.5) (–4.3, –2.85) (–4.3, +2.85) –4 (0, –5) –6 –5 –4 –3 –2 – OUTPUT VOLTAGE (V) Figure 10. Common-Mode Input Voltage vs. Output Voltage, Gain = 1, ±5 V and ±2.5 V Supplies 20 (0, +15) 15 (–14.3, +11.4) ...

Page 9

... TEMPERATURE (°C) +125°C +85°C –40°C +25°C +125°C +85°C +25° (Ω) LOAD Figure 20. Output Voltage Swing vs. R LOAD –40°C +125°C +85°C +125°C +85°C +25°C –40° CURRENT (mA) OUT AD8270 120 10k +25° ...

Page 10

... AD8270 V = ±15V S 100pF 18pF 0pF 1µs/DIV Figure 22. Small Signal Step Response, Gain = 0 ±15V S 220pF 33pF 0pF 1µs/DIV Figure 23. Small Signal Step Response, Gain = ±15V S 470pF 0pF 100pF 1µs/DIV Figure 24. Small Signal Step Response, Gain = 2 160 140 120 V = ± ...

Page 11

... Figure 31. Output Slew Rate vs. Temperature 1k GAIN = 2 100 GAIN = 0 Figure 32. Voltage Noise Spectral Density vs. Frequency, Referred to Output GAIN = 2 GAIN = 1 GAIN = 1/2 1µV/DIV Figure 33. 0 Voltage Noise, Referred to Output Rev Page AD8270 105 115 125 GAIN = 1 100 1k 10k ...

Page 12

... AD8270 210 180 150 120 –600 –400 –200 0 V (µV) OSI Figure 34. Typical Distribution of Op Amp Voltage Offset 100 310 315 320 325 330 I (nA) BIAS Figure 35. Typical Distribution of Op Amp Bias Current 160 140 120 100 ...

Page 13

... It can be farther away from the supply pins and, typically, it can be shared by other precision integrated circuits. The AD8270 is specified at ±15 V and ±5 V, but it can be used with unbalanced supplies, as well. For example, −V The difference between the two supplies must be kept below 36 V. ...

Page 14

... AD8270 INPUT VOLTAGE RANGE The AD8270 has a true rail-to-rail input range for the majority of applications. Because most AD8270 configurations divide down the voltage before they reach the internal op amp, the op amp sees only a fraction of the input voltage. Figure 41 shows an example of how the voltage division works in the difference amplifier configuration ...

Page 15

... Gain of 2, Referenced to Midsupply −IN SINGLE-ENDED CONFIGURATIONS The AD8270 can be configured for a wide variety of single- ended configurations with gains ranging from −2 to +3. Table 8 shows a subset of the possible configurations. Many signal gains have more than one configuration choice, which allows freedom in choosing the op amp closed-loop gain. ...

Page 16

... AD8270 Table 8. Selected Single-Ended Configurations Electrical Performance Op Amp Closed-Loop Gain Signal Gain −2 3 −1.5 3 −1.4 3 −1.25 3 −1 3 −0.8 3 −0.667 2 −0.6 2 −0.5 2 −0.333 2 −0.25 1.5 −0.2 1.5 −0.125 1.5 +0.1 1.5 +0.2 2 +0.25 1.5 +0.3 1.5 +0.333 2 +0.375 1.5 +0.4 2 +0.5 3 +0.5 1.5 +0.6 3 +0.6 1.5 +0.625 1.5 +0.667 2 +0.7 1.5 +0.75 3 +0.75 1.5 +0.8 2 +0.9 1.5 +1 1 +1.125 1.5 +1.2 3 +1.2 1.5 +1.25 1.5 +1.333 2 +1.5 3 +1.5 1.5 +1.6 2 +1.667 2 +1 ...

Page 17

... Gain of 1 Configuration The AD8270 is designed to be stable for loop gains of 1.5 and greater. Because a typical voltage follower configuration has a loop gain may be unstable. Several stable configu- rations are listed in Table 8. DIFFERENTIAL OUTPUT The AD8270 can easily be configured for differential output. ...

Page 18

... AD8270 is operating in a gain of 0.5. –IN +IN 5V_REF 0.1µF –IN +IN To reduce the peaking, use a resistor between the AD8270 and the cable. Because cable capacitance and desired output response vary widely, this resistor is best determined empirically. A good starting point is 20 Ω. AD7688 ADC. The +12V –12V ...

Page 19

... Figure 52. 16-Lead Lead Frame Chip Scale Package [LFCSP_VQ × Body, Very Thin Quad (CP-16-10) Dimensions are shown in millimeters Package Description 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ 16-Lead LFCSP_VQ Rev Page 0.60 MAX PIN 1 INDICATOR 2.50 EXPOSED 2.35 SQ PAD (BOTTOM VIEW) 2. 0.25 MIN 1.95 BSC Package Option CP-16-10 CP-16-10 CP-16-10 AD8270 ...

Page 20

... AD8270 NOTES ©2008 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06979-0-1/08(0) Rev Page ...

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