Datasheet

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18 V, Precision, Micropower

CMOS RRIO Operational Amplifier

AD8657

Rev. A

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FEATURES

Micropower at high voltage (18 V): 18 A typical

Low offset voltage: 350 µV maximum

Single-supply operation: 2.7 V to 18 V

Dual-supply operation: ±1.35 V to ±9 V

Low input bias current: 20 pA

Gain bandwidth: 200 kHz

Unity-gain stable

Excellent electromagnetic interference immunity

APPLICATIONS

Portable operating systems

Current monitors

4 mA to 20 mA loop drivers

Buffer/level shifting

Multipole filters

Remote/wireless sensors

Low power transimpedance amplifiers

PIN CONFIGURATION

OUT A 1

–IN A 2

+IN A 3

V– 4

V+8

OUT B7

–IN B6

+IN B5

AD8657

TOP VIEW

(Not to Scale)

08804-001

Figure 1. 8-Lead MSOP

08804-061

AD8657

TOP VIEW

(Not to Scale)

NOTES

1. IT IS RECOMMENDED TO CONNECT

THE EXPOSED PAD TO V–.

3+IN A

4V–

UT A

2–IN A

6 –IN B

5 +IN B

8V+

7OUT B

Figure 2. 8-Lead LFCSP

GENERAL DESCRIPTION

The AD8657 is a dual, micropower, precision, rail-to-rail

input/output amplifier optimized for low power and wide

operating supply voltage range applications.

The AD8657 operates from 2.7 V up to 18 V with a typical

quiescent supply current of 18 μA. It uses the Analog Devices,

Inc., patented DigiTrim® trimming technique, which achieves

low offset voltage. The AD8657 also has high immunity to

electromagnetic interference.

The combination of low supply current, low offset voltage, very

low input bias current, wide supply range, and rail-to-rail input

and output makes the AD8657 ideal for current monitoring and

current loops in process and motor control applications. The

combination of precision specifications makes this device ideal

for dc gain and buffering of sensor front ends or high impedance

input sources in wireless or remote sensors or transmitters.

The AD8657 is specified over the extended industrial tempera-

ture range (−40°C to +125°C) and is available in an 8-lead MSOP

package and an 8-lead LFCSP package.

Table 1. Micropower Op Amps

Supply Voltage 5 V 12 V to 16 V 36 V

Single AD8500 AD8663

ADA4505-1

AD8505

AD8541

AD8603

Dual AD8502 AD8667 OP295

ADA4505-2 OP281 ADA4062-2

AD8506

AD8542

AD8607

Quad AD8504 AD8669 OP495

ADA4505-4 OP481 ADA4062-4

AD8508

AD8544

AD8609

Summary of content (24 pages)

PAGE 1
8 V, Precision, Micropower CMOS RRIO Operational Amplifier AD8657 PIN CONFIGURATION Micropower at high voltage (18 V): 18 μA typical Low offset voltage: 350 μV maximum Single-supply operation: 2.7 V to 18 V Dual-supply operation: ±1.
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AD8657 TABLE OF CONTENTS Features .............................................................................................. 1 Applications Information .............................................................. 17 Applications ....................................................................................... 1 Input Stage ................................................................................... 17 Pin Configuration ..................................................................
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AD8657 SPECIFICATIONS ELECTRICAL CHARACTERISTICS—2.7 V OPERATION VSY = 2.7 V, VCM = VSY/2 V, TA = 25°C, unless otherwise specified. Table 2. Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current Symbol Test Conditions/Comments VOS VCM = 0 V to 2.7 V VCM = 0.3 V to 2.4 V; −40°C ≤ TA ≤ +85°C VCM = 0.3 V to 2.4 V; −40°C ≤ TA ≤ +125°C VCM = 0 V to 2.7 V; −40°C ≤ TA ≤ +125°C Min IB Typ Max Unit 1 350 1 2.5 4 10 2.6 20 500 2.
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AD8657 ELECTRICAL CHARACTERISTICS—10 V OPERATION VSY = 10 V, VCM = VSY/2 V, TA = 25°C, unless otherwise specified. Table 3.
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AD8657 ELECTRICAL CHARACTERISTICS—18 V OPERATION VSY = 18 V, VCM = VSY/2 V, TA = 25°C, unless otherwise specified. Table 4. Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current Symbol Test Conditions/Comments VOS VCM = 0 V to 18 V VCM = 0.3 V to 17.7 V; −40°C ≤ TA ≤ +85°C VCM = 0.3 V to 17.7 V; −40°C ≤ TA ≤ +125°C VCM = 0 V to 18 V; −40°C ≤ TA ≤ +125°C Min IB Typ Max Unit 5 350 1.2 2 11 20 2.
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AD8657 ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE Table 4. Parameter Supply Voltage Input Voltage Input Current1 Differential Input Voltage Output Short-Circuit Duration to GND Temperature Range Storage Operating Junction Lead Temperature (Soldering, 60 sec) 1 Rating 20.
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AD8657 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. 160 160 VSY = 2.7V VCM = VSY/2 120 NUMBER OF AMPLIFIERS 140 08804-005 120 80 100 60 Figure 6. Input Offset Voltage Distribution 18 20 VSY = 2.7V –40°C ≤ TA ≤ +125°C 16 VSY = 18V –40°C ≤ TA ≤ +125°C 18 16 14 NUMBER OF AMPLIFIERS 12 10 8 6 4 14 12 10 8 6 4 2 2 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 TCVOS (µV/°C) 0 TCVOS (µV/°C) Figure 4. Input Offset Voltage Drift Distribution Figure 7.
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AD8657 4 VSY = 2.7V –40°C ≤ TA ≤ +85°C 2 0.5 1 VOS (mV) 1.0 0 0 –0.5 –1 –1.0 –2 –1.5 –3 –2.0 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 VSY = 18V –40°C ≤ TA ≤ +85°C 3 2.7 VCM (V) –4 08804-108 VOS (mV) 1.5 0 2 4 6 8 10 VCM (V) 12 14 16 18 08804-111 2.0 Figure 12. Input Offset Voltage vs. Common-Mode Voltage Figure 9. Input Offset Voltage vs. Common-Mode Voltage 6 2.0 VSY = 2.7V –40°C ≤ TA ≤ +125°C 1.5 VSY = 18V –40°C ≤ TA ≤ +125°C 4 1.0 2 VOS (mV) VOS (mV) 0.
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AD8657 4 4 VSY = 18V 3 3 2 2 1 1 IB (nA) 0 125°C 85°C 25°C –1 –2 –2 –3 –3 0.9 1.2 1.5 1.8 2.1 2.4 2.7 VCM (V) 0 2 4 6 8 10 12 14 16 Figure 18. Input Bias Current vs. Common-Mode Voltage 10 10 OUTPUT VOLTAGE (VOH) TO SUPPLY RAIL (V) Figure 15. Input Bias Current vs. Common-Mode Voltage VSY = 2.7V 1 –40°C +25°C +85°C +125°C 100m 10m 1m 0.01 0.1 1 LOAD CURRENT (mA) 10 100 VSY = 18V 1 –40°C +25°C +85°C +125°C 100m 10m 1m 0.1m 0.01m 0.001 08804-010 0.1m 0.
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AD8657 2.700 18.000 RL = 1MΩ RL = 1MΩ OUTPUT VOLTAGE, VOH (V) 2.698 2.697 RL = 100kΩ 17.995 17.990 17.985 RL = 100kΩ 17.980 2.696 VSY = 2.7V 0 –25 25 50 75 100 125 TEMPERATURE (°C) 08804-015 2.695 –50 VSY = 18V 17.975 –50 0 25 50 75 100 125 TEMPERATURE (°C) Figure 24. Output Voltage (VOH) vs. Temperature Figure 21. Output Voltage (VOH) vs. Temperature 12 12 VSY = 18V VSY = 2.
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AD8657 60 35 30 50 VSY = 2.7V VSY = 18V ISY PER AMP (µA) ISY PER AMP (µA) 25 20 15 40 30 20 10 –40°C +25°C 5 10 +85°C 9 12 15 18 VSY (V) 0 –50 Figure 27. Supply Current vs. Supply Voltage 135 GAIN 0 –45 –20 CL = 10pF OPEN-LOOP GAIN (dB) 45 PHASE (Degrees) 20 –90 CL = 100pF –135 1M 100k FREQUENCY (Hz) 90 20 45 0 0 GAIN –45 –20 CL = 10pF 10k Figure 31. Open-Loop Gain and Phase vs. Frequency 60 VSY = 2.
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AD8657 1000 1000 AV = 100 AV = 100 AV = 10 AV = 10 100 100 AV = 1 ZOUT (Ω) ZOUT (Ω) AV = 1 10 10 1k 10k FREQUENCY (Hz) 100k 08804-026 100 1 100 Figure 33. Output Impedance vs. Frequency 140 VSY = 2.7V VCM = 2.4V 120 VSY = 18V VCM = VSY/2 80 60 80 60 40 40 20 20 1k 10k 100k 1M FREQUENCY (Hz) 0 100 1k 10k Figure 34. CMRR vs. Frequency 100 VSY = 2.7V VSY = 18V 80 60 60 PSRR (dB) 80 PSRR+ PSRR– 40 20 PSRR+ PSRR– 40 1k 10k 100k FREQUENCY (Hz) 1M Figure 35.
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AD8657 70 70 VSY = 2.7V VIN = 10mV p-p RL = 1MΩ 60 OS+ OS– OS+ OS– 50 40 30 40 30 20 20 10 10 100 1000 CAPACITANCE (pF) 0 10 08804-032 100 1000 CAPACITANCE (pF) Figure 39. Small Signal Overshoot vs. Load Capacitance Figure 42. Small Signal Overshoot vs. Load Capacitance VSY = ±1.35V AV = 1 RL = 1MΩ CL = 100pF TIME (100µs/DIV) TIME (100µs/DIV) Figure 40. Large Signal Transient Response Figure 43.
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AD8657 INPUT 2 INPUT VOLTAGE (V) VSY = ±1.35 AV = –10 RL = 1MΩ –0.4 OUTPUT VOLTAGE (V) –1 –2 10 1 5 OUTPUT OUTPUT 0 TIME (40µs/DIV) TIME (40µs/DIV) Figure 45. Positive Overload Recovery Figure 48. Positive Overload Recovery VSY = ±9V AV = –10 RL = 1MΩ 2 0.4 0 OUTPUT 0 –1 –5 –2 –10 08804-038 VSY = ±1.35V AV = –10 RL = 1MΩ INPUT 0 TIME (40µs/DIV) TIME (40µs/DIV) Figure 46. Negative Overload Recovery Figure 49.
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AD8657 VSY =18V RL = 100kΩ CL = 10pF VOLTAGE (500mV/DIV) VOLTAGE (500mV/DIV) VSY = 2.7V RL = 100kΩ CL = 10pF INPUT +5mV OUTPUT 0 ERROR BAND INPUT +5mV OUTPUT –5mV TIME (10µs/DIV) Figure 51. Negative Settling Time to 0.1% Figure 54. Negative Settling Time to 0.1% 1000 1000 VSY = 18V 100 1 100 1k 10k FREQUENCY (Hz) 100k 1M 1 10 Figure 52. Voltage Noise Density vs. Frequency 100 1k 10k FREQUENCY (Hz) 100k 1M Figure 55. Voltage Noise Density vs. Frequency VSY = 2.
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AD8657 20 3.0 VSY = 2.7V VIN = 2.6V RL = 1MΩ AV = 1 VSY = 18V VIN = 17.9V RL = 1MΩ AV = 1 18 16 OUTPUT SWING (V) OUTPUT SWING (V) 2.5 2.0 1.5 1.0 14 12 10 8 6 4 0.5 0 100 1k 10k 100k 1M FREQUENCY (Hz) 08804-050 0 10 10 10k 100k 1M Figure 60. Output Swing vs. Frequency 100 100 VSY = 2.7V VIN = 0.2V rms RL = 1MΩ AV = 1 VSY = 18V VIN = 0.2V rms RL = 1MΩ AV = 1 10 THD + N (%) 10 1 0.1 100 1k 10k 100k FREQUENCY (Hz) 0.01 10 08804-051 0.
PAGE 17
AD8657 APPLICATIONS INFORMATION The AD8657 is a low power, rail-to-rail input and output precision CMOS amplifier that operates over a wide supply voltage range of 2.7 V to 18 V. This amplifier uses the Analog Devices DigiTrim technique to achieve a higher degree of precision than is available from other CMOS amplifiers. The DigiTrim technique is a method of trimming the offset voltage of an amplifier after assembly.
PAGE 18
AD8657 V+ I1 VB1 M5 +IN x R1 –IN x R2 M3 D1 M8 M9 M10 M11 M4 M16 D2 VB2 M1 OUT x M2 M7 M6 M13 M14 M15 08804-056 M17 M12 V– Figure 63. Simplified Schematic RAIL TO RAIL Inverting Configuration The AD8657 features rail-to-rail input and output with a supply voltage from 2.7 V to 18 V. Figure 64 shows the input and output waveforms of the AD8657 configured as a unity-gain buffer with a supply voltage of ±9 V and a resistive load of 1 MΩ.
PAGE 19
AD8657 COMPARATOR OPERATION Op amps are designed to operate in a closed-loop configuration with feedback from its output to its inverting input. Figure 67 shows the AD8657 configured as a voltage follower with an input voltage that is always kept at midpoint of the power supplies. The same configuration is applied to the unused channel. A1 and A2 indicate the placement of ammeters to measure supply current.
PAGE 20
AD8657 EMI REJECTION RATIO Circuit performance is often adversely affected by high frequency electromagnetic interference (EMI). In the event where signal strength is low and transmission lines are long, an op amp must accurately amplify the input signals. However, all op amp pins— the noninverting input, inverting input, positive supply, negative supply, and output pins—are susceptible to EMI signals.
PAGE 21
AD8657 OUTLINE DIMENSIONS 3.20 3.00 2.80 8 3.20 3.00 2.80 1 5.15 4.90 4.65 5 4 PIN 1 IDENTIFIER 0.65 BSC 0.95 0.85 0.75 15° MAX 1.10 MAX 0.40 0.25 0.80 0.55 0.40 0.23 0.09 6° 0° 100709-B 0.15 0.05 COPLANARITY 0.10 COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 74. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters 2.44 2.34 2.24 3.10 3.00 SQ 2.90 0.50 BSC 8 5 1.70 1.60 1.50 EXPOSED PAD 0.50 0.40 0.30 0.80 0.75 0.70 SEATING PLANE 0.30 0.25 0.
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AD8657 NOTES Rev.
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AD8657 NOTES Rev.