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| Low Cost, High Speed Rail-to-Rail Amplifiers AD8091/AD8092 FEATURES Low cost single (AD8091), dual (AD8092) amplifiers Fully specified at +3 V, +5 V, and 5 V supplies Single-supply operation Output swings to within 25 mV of either rail High-speed and fast settling on 5 V 110 MHz, -3 dB bandwidth (G = +1) 145 V/s slew rate 50 ns settling time to 0.1% Good video specifications (G = +2) Gain flatness of 0.1 dB to 20 MHz; RL = 150 0.03% differential gain error; RL = 1 k 0.03 differential phase error; RL = 1 k Low distortion -80 dBc total harmonic @ 1 MHz; RL = 100 Outstanding load drive capability Drives 45 mA, 0.5 V from supply rails Drives 50 pF capacitive load (G = +1) Low power of 4.4 mA/Amplifier CONNECTION DIAGRAMS NC 1 -IN 2 +IN 3 -VS 4 AD8091 8 7 6 5 NC +VS VOUT 02859-001 NC NC = NO CONNECT Figure 1. SOIC-8 (R-8) VOUT 1 -VS 2 +IN 3 4 AD8091 5 +VS 02859-003 02859-002 -IN Figure 2. SOT23-5 (RT-5) OUT1 1 -IN1 2 +IN1 3 -VS 4 AD8092 8 7 6 5 +VS OUT -IN2 +IN2 NC = NO CONNECT APPLICATIONS Coaxial cable drivers Active filters Video switchers Professional cameras CCD imaging systems CDs/DVDs Figure 3. MSOP-8 and SOIC-8 (RM-8, R-8) GENERAL DESCRIPTION The AD8091 (single) and AD8092 (dual) are low cost, voltage feedback, high speed amplifiers designed to operate on +3 V, +5 V, or 5 V supplies. They have true single-supply capability, with an input voltage range extending 200 mV below the negative rail and within 1 V of the positive rail. Despite their low cost, the AD8091/AD8092 provide excellent overall performance and versatility. The output voltage swing extends to within 25 mV of each rail, providing the maximum output dynamic range with excellent overdrive recovery. This makes the AD8091/AD8092 useful for video electronics, such as cameras, video switchers, or any high speed portable equipment. Low distortion and fast settling make them ideal for active filter applications. The AD8091/AD8092 offer a low power supply current and can operate on a single 3 V power supply. These features are ideally suited for portable and battery-powered applications where size and power are critical. The wide bandwidth and fast slew rate make these amplifiers useful in many general-purpose, high speed applications where dual power supplies of up to 6 V and single supplies from +3 V to +12 V are needed. This low cost performance is offered in an 8-lead SOIC (AD8091/AD8092), along with a tiny SOT23-5 (AD8091) and a MSOP (AD8092). Rev. B 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. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c) 2005 Analog Devices, Inc. All rights reserved. A8091/AD8092 TABLE OF CONTENTS Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 7 Maximum Power Dissipation ..................................................... 7 ESD Caution.................................................................................. 7 Typical Performance Characteristics ............................................. 9 Layout, Grounding, and Bypassing Considerations .................. 13 Power Supply Bypassing ............................................................ 13 Grounding ................................................................................... 13 Input Capacitance....................................................................... 13 Input-to-Output Coupling ........................................................ 13 Driving Capacitive Loads .............................................................. 14 Overdrive Recovery ................................................................... 14 Active Filters ............................................................................... 14 Sync Stripper ............................................................................... 15 Single-Supply Composite Video Line Driver ......................... 15 Outline Dimensions ....................................................................... 17 Ordering Guide .......................................................................... 18 REVISION HISTORY 3/05--Rev. A to Rev. B Changes to Format .............................................................Universal Changes to Features.......................................................................... 1 Updated Outline Dimensions ....................................................... 17 Changes to Ordering Guide .......................................................... 18 5/02-Rev. 0 to Rev. A Edits to Product Description ...........................................................1 Edit to TPC 6 .....................................................................................7 Edits to TPCs 21-24........................................................................10 Edits to Figure 3 ...............................................................................11 2/02--Revision 0: Initial Version Rev. B | Page 2 of 20 AD8091/AD8092 SPECIFICATIONS TA = 25C, VS = 5 V, RL = 2 k to 2.5 V, unless otherwise noted. Table 1. Parameter DYNAMIC PERFORMANCE -3 dB Small Signal Bandwidth Bandwidth for 0.1 dB Flatness Slew Rate Full Power Response Settling Time to 0.1% NOISE/DISTORTION PERFORMANCE Total Harmonic Distortion (See Figure 11) Input Voltage Noise Input Current Noise Differential Gain Error (NTSC) Differential Phase Error (NTSC) Crosstalk DC PERFORMANCE Input Offset Voltage Offset Drift Input Bias Current TMIN to TMAX Input Offset Current Open-Loop Gain RL = 2 k to 2.5 V TMIN to TMAX RL = 150 to 2.5 V TMIN to TMAX 86 76 0.1 98 96 82 78 290 1.4 -0.2 to +4 88 0.015 to 4.985 0.025 to 4.975 0.200 to 4.800 45 45 80 130 50 12 5 +85 Conditions G = +1, VO = 0.2 V p-p G = -1, +2, VO = 0.2 V p-p G = +2, VO = 0.2 V p-p, RL = 150 to 2.5 V, RF = 806 G = -1, VO = 2 V step G = +1, VO = 2 V p-p G = -1, VO = 2 V step fC = 5 MHz, VO = 2 V p-p, G = +2 f = 10 kHz f = 10 kHz G = +2, RL = 150 to 2.5 V RL = 1 k to 2.5 V G = +2, RL = 150 to 2.5 V RL = 1 k to 2.5 V f = 5 MHz, G = +2 Min 70 AD8091A/AD8092A Typ 110 50 20 145 35 50 -67 16 850 0.09 0.03 0.19 0.03 -60 1.7 TMIN to TMAX 10 1.4 10 25 2.5 3.25 0.75 Max Unit MHz MHz MHz V/s MHz ns dB nV/Hz fA/Hz % % Degrees Degrees dB mV mV V/C A A A dB dB dB dB k pF V dB V V V mA mA mA mA pF V mA dB C 100 INPUT CHARACTERISTICS Input Resistance Input Capacitance Input Common-Mode Voltage Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing VCM = 0 V to 3.5 V RL = 10 k to 2.5 V RL = 2 k to 2.5 V RL = 150 to 2.5 V VOUT = 0.5 V to 4.5 V TMIN to TMAX Sourcing Sinking G = +1 72 0.100 to 4.900 0.300 to 4.625 Output Current Short-Circuit Current Capacitive Load Drive POWER SUPPLY Operating Range Quiescent Current/Amplifier Power Supply Rejection Ratio OPERATING TEMPERATURE RANGE 3 VS = 1 V 70 -40 Rev. B | Page 3 of 20 4.4 80 A8091/AD8092 TA = 25C, VS = +3 V, RL = 2 k to +1.5 V, unless otherwise noted. Table 2. Parameter DYNAMIC PERFORMANCE -3 dB Small Signal Bandwidth Bandwidth for 0.1 dB Flatness Slew Rate Full Power Response Settling Time to 0.1% NOISE/DISTORTION PERFORMANCE Total Harmonic Distortion (see Figure 11) Input Voltage Noise Input Current Noise Differential Gain Error (NTSC) Conditions G = +1, VO = 0.2 V p-p G = -1, +2, VO = 0.2 V p-p G = +2, VO = 0.2 V p-p, RL = 150 to 2.5 V, RF = 402 G = -1, VO = 2 V step G = +1, VO = 1 V p-p G = -1, VO = 2 V step fC = 5 MHz, VO = 2 V p-p, G = -1, RL = 100 to 1.5 V f = 10 kHz f = 10 kHz G = +2, VCM = 1 V RL = 150 to 1.5 V RL = 1 k to 1.5 V G = +2, VCM = 1 V RL = 150 to 1.5 V RL = 1 k to 1.5 V f = 5 MHz, G = +2 Min 70 AD8091A/AD8092A Typ 110 50 17 135 65 55 -47 16 600 0.11 0.09 0.24 0.10 -60 1.6 TMIN to TMAX Offset Drift Input Bias Current TMIN to TMAX Input Offset Current Open-Loop Gain RL = 2 k TMIN to TMAX RL = 150 TMIN to TMAX 80 74 0.15 96 94 82 76 290 1.4 -0.2 to +2.0 88 0.01 to 2.99 0.02 to 2.98 0.125 to 2.875 45 45 60 90 45 10 1.3 10 25 2.6 3.25 0.8 Max Unit MHz MHz MHz V/s MHz ns dB nV/Hz fA/Hz % % Degrees Degrees dB mV mV V/C A A A dB dB dB dB k pF V dB V V V mA mA mA mA pF 90 Differential Phase Error (NTSC) Crosstalk DC PERFORMANCE Input Offset Voltage INPUT CHARACTERISTICS Input Resistance Input Capacitance Input Common-Mode Voltage Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing VCM = 0 V to 1.5 V RL = 10 k to 1.5 V RL = 2 k to 1.5 V RL = 150 to 1.5 V VOUT = 0.5 V to 2.5 V TMIN to TMAX Sourcing Sinking G = +1 72 0.075 to 2.9 0.20 to 2.75 Output Current Short Circuit Current Capacitive Load Drive Rev. B | Page 4 of 20 AD8091/AD8092 Parameter POWER SUPPLY Operating Range Quiescent Current/Amplifier Power Supply Rejection Ratio OPERATING TEMPERATURE RANGE Conditions Min 3 VS = +0.5 V 68 -40 4.2 80 AD8091A/AD8092A Typ Max 12 4.8 +85 Unit V mA dB C Rev. B | Page 5 of 20 A8091/AD8092 TA = 25C, VS = 5 V, RL = 2 k to ground, unless otherwise noted. Table 3. Parameter DYNAMIC PERFORMANCE -3 dB Small Signal Bandwidth Bandwidth for 0.1 dB Flatness Slew Rate Full Power Response Settling Time to 0.1% NOISE/DISTORTION PERFORMANCE Total Harmonic Distortion Input Voltage Noise Input Current Noise Differential Gain Error (NTSC) Differential Phase Error (NTSC) Crosstalk DC PERFORMANCE Input Offset Voltage Offset Drift Input Bias Current TMIN to TMAX Input Offset Current Open-Loop Gain RL = 2 k TMIN to TMAX RL = 150 TMIN to TMAX 88 78 0.1 96 96 82 80 290 1.4 -5.2 to +4.0 88 -4.98 to +4.98 -4.97 to +4.97 -4.60 to +4.60 45 45 100 160 50 12 5.5 +85 Conditions G = +1, VO = 0.2 V p-p G = -1, +2, VO = 0.2 V p-p G = +2, VO = 0.2 V p-p, RL = 150 , RF = 1.1 k G = -1, VO = 2 V step G = +1, VO = 2 V p-p G = -1, VO = 2 V step fC = 5 MHz, VO = 2 V p-p, G = +2 f = 10 kHz f = 10 kHz G = +2, RL = 150 RL = 1 k G = +2, RL = 150 RL = 1 k f = 5 MHz, G = +2 Min 70 AD8091A/AD8092A Typ 110 50 20 170 40 50 -71 16 900 0.02 0.02 0.11 0.02 -60 1.8 TMIN to TMAX 10 1.4 11 27 2.6 3.5 0.75 Max Unit MHz MHz MHz V/s MHz ns dB nV/Hz fA/Hz % % Degrees Degrees dB mV mV V/C A A A dB dB dB dB k pF V dB V V V mA mA mA mA pF V mA dB C 105 INPUT CHARACTERISTICS Input Resistance Input Capacitance Input Common-Mode Voltage Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing VCM = -5 V to +3.5 V RL = 10 k RL = 2 k RL = 150 VOUT = -4.5 V to +4.5 V TMIN to TMAX Sourcing Sinking G = +1 (AD8091/AD8092) 72 -4.85 to +4.85 -4.45 to +4.30 Output Current Short Circuit Current Capacitive Load Drive POWER SUPPLY Operating Range Quiescent Current/Amplifier Power Supply Rejection Ratio OPERATING TEMPERATURE RANGE 3 VS = 1 V 68 -40 4.8 80 Rev. B | Page 6 of 20 AD8091/AD8092 ABSOLUTE MAXIMUM RATINGS Table 4. Parameter Supply Voltage Power Dissipation Common-Mode Input Voltage Differential Input Voltage Output Short-Circuit Duration Storage Temperature Range Operating Temperature Range Lead Temperature Range (Soldering 10 sec) Rating 12.6 V See Figure 4 VS 2.5 V See Figure 4 -65C to +125C -40C to +85C 300C The still-air thermal properties of the package (JA), ambient temperature (TA), and the total power dissipated in the package (PD) can be used to determine the junction temperature of the die. The junction temperature can be calculated as TJ = TA + (PD x JA ) The power dissipated in the package (PD) is the sum of the quiescent power dissipation and the power dissipated in the package due to the load drive for all outputs. The quiescent power is the voltage between the supply pins (VS) times the quiescent current (IS). Assuming the load (RL) is referenced to midsupply, then the total drive power is VS/2 x IOUT, some of which is dissipated in the package and some in the load (VOUT x IOUT). The difference between the total drive power and the load power is the drive power dissipated in the package. 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. PD = quiescent power + (total drive power - load power ) V V V 2 PD = (VS x I S ) + S x OUT - OUT RL RL 2 RMS output voltages should be considered. If RL is referenced to VS-, as in single-supply operation, then the total drive power is VS x IOUT. If the rms signal levels are indeterminate, then consider the worst case, when VOUT = VS/4 for RL to midsupply VS 4 PD = (VS x I S ) + RL 2 MAXIMUM POWER DISSIPATION The maximum safe power dissipation in the AD8091/AD8092 package is limited by the associated rise in junction temperature (TJ) on the die. The plastic encapsulating the die locally reaches the junction temperature. At approximately 150C, which is the glass transition temperature, the plastic changes its properties. Even temporarily exceeding this temperature limit may change the stresses that the package exerts on the die, permanently shifting the parametric performance of the AD8091/AD8092. Exceeding a junction temperature of 175C for an extended period of time can result in changes in the silicon devices, potentially causing failure. In single-supply operation with RL referenced to VS-, worst case is VOUT = VS/2. ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. B | Page 7 of 20 A8091/AD8092 MAXIMUM POWER DISSIPATION (W) Airflow increases heat dissipation, effectively reducing JA. Also, more metal directly in contact with the package leads from metal traces, through holes, ground, and power planes reduces the JA. Care must be taken to minimize parasitic capacitances at the input leads of high speed op amps as discussed in the board layout section. Figure 4 shows the maximum safe power dissipation in the package vs. the ambient temperature for the SOIC-8 (125C/W), SOT23-5 (180C/W), and MSOP-8 (150C/W) on a JEDEC standard four-layer board. 2.0 TJ = 150C 1.5 SOIC-8 MSOP-8 1.0 SOT23-5 0.5 02859-004 0 -40 -30 -20 -10 0 10 20 30 40 50 60 AMBIENT TEMPERATURE (C) 70 80 90 Figure 4. Maximum Power Dissipation vs. Temperature for a Four-Layer Board Rev. B | Page 8 of 20 AD8091/AD8092 TYPICAL PERFORMANCE CHARACTERISTICS 3 2 1 G = +2 RF = 2k 6.3 6.2 6.1 NORMALIZED GAIN (dB) -1 -2 -3 -4 -5 -6 -7 0.1 VS = 5V GAIN AS SHOWN RF AS SHOWN RL = 2k VO = 0.2V p-p 1 G = +10 RF = 2k G = +5 RF = 2k GAIN FLATNESS (dB) 02859-005 0 6.0 5.9 5.8 5.7 5.6 VS = 5V 5.5 G = +2 RL = 150k 5.4 RF = 806 VO = 0.2V p-p 5.3 0.1 G = +1 RF = 0 10 FREQUENCY (MHz) 100 500 1 10 FREQUENCY (MHz) 100 Figure 5. Normalized Gain vs. Frequency; VS = +5 V Figure 8. 0.1 dB Gain Flatness vs. Frequency; G = +2 3 2 VS = +3V 1 0 VS = +5V 9 8 7 6 VS = 5V GAIN (dB) GAIN (dB) -1 -2 -3 -4 -5 VS AS SHOWN G = +1 -6 RL = 2k VO = 0.2V p-p -7 0.1 1 5 4 3 2 VS AS SHOWN 1 G = +2 RL = 2k 0 RF = 2k VO AS SHOWN -1 0.1 1 VS = 5V VO = 4V p-p VS = +5V VO = 2V p-p 02859-006 10 FREQUENCY (MHz) 100 500 10 FREQUENCY (MHz) 100 500 Figure 6. Gain vs. Frequency vs. Supply Figure 9. Large Signal Frequency Response; G = +2 3 2 -40C 1 0 +85C 70 60 50 VS = 5V RL = 2k OPEN-LOOP GAIN (dB) GAIN (dB) -1 +25C -2 -3 -4 VS = 5V -5 G = +1 RL = 2k -6 VO = 0.2V p-p TEMPERATURE AS SHOWN -7 0.1 1 10 FREQUENCY (MHz) GAIN 30 20 10 0 PHASE 0 -45 -90 -135 -180 02859-007 -10 -20 0.1 100 500 1 10 FREQUENCY (MHz) 100 500 Figure 7. Gain vs. Frequency vs. Temperature Figure 10. Open-Loop Gain and Phase vs. Frequency Rev. B | Page 9 of 20 02859-010 50 PHASE MARGIN PHASE (Degrees) 40 02859-009 02859-008 A8091/AD8092 -20 TOTAL HARMONIC DISTORTION (dBc) -30 -40 -50 -60 VS = 5V, G = +1 RL = 100 VS = 3V, G = -1 RF = 2k, RL = 100 VS = 5V, G = +2 RF = 2k, RL = 100 DIFFERENTIAL GAIN ERROR (%) VO = 2V p-p 0.10 0.08 0.06 0.04 0.02 0 -0.02 -0.04 -0.06 0.10 0.05 0 -0.05 -0.10 -0.15 -0.20 -0.25 NTSC SUBSCRIBER (3.58MHz) RL = 150 VS = 5, G = +2 RF = 2k, RL AS SHOWN 0 10 20 30 40 50 60 RL = 1k 70 80 90 100 -70 -80 -90 -100 -110 1 2 3 4 5 6 FUNDAMENTAL FREQUENCY (MHz) 7 8 9 10 VS = 5V, G = +2 RF = 2k, RL = 2k 02859-011 DIFFERENTIAL PHASE ERROR (Degrees) RL = 1k VS = 5V, G = +1 RL = 2k RL = 150 VS = 5, G = +2 RF = 2k, RL AS SHOWN 0 10 20 30 40 50 60 70 80 90 100 02859-014 MODULATING RAMP LEVEL (IRE) Figure 11. Total Harmonic Distortion Figure 14. Differential Gain and Phase Errors -30 -40 10MHz -50 1000 VS = 5V WORST HARMONIC (dBc) -60 -70 -80 -90 1MHz -100 -110 02859-012 VOLTAGE NOISE (nA Hz) 100 5MHz 10 -120 -130 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 OUTPUT VOLTAGE (V p-p) 4.0 4.5 5.0 1 10 100 1k 10k 100k FREQUENCY (Hz) 1M 10M Figure 12. Worst Harmonic vs. Output Voltage Figure 15. Input Voltage Noise vs. Frequency 5.0 100 VS = 5V G = -1 RF = 2k RL = 2k VS = 5V OUTPUT VOLTAGE SWING (THD 0.5%) (V p-p) 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 CURRENT NOISE (pA Hz) 10 1 02859-013 0.5 0 0.1 1 FREQUENCY (MHz) 10 50 0.1 10 100 1k 10k 100k FREQUENCY (Hz) 1M 10M Figure 13. Low Distortion Rail-to-Rail Output Swing Figure 16. Input Current Noise vs. Frequency Rev. B | Page 10 of 20 02859-016 02859-015 VS = 5V RL = 2k G = +2 AD8091/AD8092 -10 VS = 5V RF = 2k -20 RL = 2k VO = 2V p-p -30 20 VS = 5V 10 0 -10 -PSRR CROSSTALK (dB) -40 -50 -60 -70 -80 02859-017 PSRR (dB) -20 +PSRR -30 -40 -50 -60 -70 -80 0.01 02859-020 -90 -100 0.1 1 10 FREQUENCY (MHz) 100 500 0.1 1 10 FREQUENCY (MHz) 100 500 Figure 17. AD8092 Crosstalk (Output-to-Output) vs. Frequency Figure 20. PSRR vs. Frequency 0 VS = 5V -10 70 60 VS = 5V G = -1 RL = 2k SETTLING TIME TO 0.1% (ns) 02859-018 -20 -30 50 CMRR (dB) -40 -50 -60 -70 -80 -90 -100 0.03 40 30 20 10 0 0.5 0.1 1 10 FREQUENCY (MHz) 100 500 1.0 1.5 INPUT STEPS (V p-p) 2.0 Figure 18. CMRR vs. Frequency Figure 21. Setting Time vs. Input Step 100.000 31.000 VS = 5V G = +1 1.0 VS = 5V 0.9 VOH = +85C VOH = +25C VOH = -40C 0.6 0.5 0.4 0.3 0.2 0.1 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 LOAD CURRENT (mA) VOL = +25C VOL = -40C 02859-022 OUTPUT SATURATION VOLTAGE (V) 0.8 0.7 OUTPUT RESISTANCE () 10.000 3.100 1.000 0.310 0.100 02859-019 VOL = +85C 0.031 0.010 0.1 1 10 FREQUENCY (MHz) 100 500 Figure 19. Closed-Loop Output Resistance vs. Frequency Figure 22. Output Saturation Voltage vs. Load Current Rev. B | Page 11 of 20 02859-021 A8091/AD8092 100 RL = 2k OPEN-LOOP GAIN (dB) 90 VS = 5V G = +2 RL = 2k VIN = 1V p-p 3.5V RL = 150 80 2.5V 1.5V 70 02859-023 VS = 5V 60 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 OUTPUT VOLTAGE (V) 4.0 4.5 5.0 Figure 26. Large Signal Step Response; VS = +5 V, G = +2 Figure 23. Open-Loop Gain vs. Output Voltage VS = 5V G = -1 RF = 2k RL = 2k 5V VIN = 0.1V p-p G = +1 RL = 2k VS = 3V 2.5V 1.50V 1V 02859-024 2s 20mV 20ns Figure 27. Output Swing; G = -1, RL = 2 k Figure 24. 100 mV Step Response; G = +1 4V 3V VS = 5V G = +1 RL = 2k VS = 5V G = +1 RL = 2k 2.60V 2V 1V -1V 2.50V -2V -3V 02859-028 2.40V -4V 1V 02859-025 20ns 50mV 20ns Figure 28. Large Signal Step Response; VS = 5 V, G = +1 Figure 25. 200 mV Step Response; VS = +5 V, G = +1 Rev. B | Page 12 of 20 02859-027 02859-026 AD8091/AD8092 LAYOUT, GROUNDING, AND BYPASSING CONSIDERATIONS POWER SUPPLY BYPASSING Power supply pins are actually inputs and care must be taken so that a noise-free stable dc voltage is applied. The purpose of bypass capacitors is to create low impedances from the supply to ground at all frequencies, thereby shunting or filtering a majority of the noise. Decoupling schemes are designed to minimize the bypassing impedance at all frequencies with a parallel combination of capacitors. Chip capacitors of 0.01 F or 0.001 F (X7R or NPO) are critical and should be as close as possible to the amplifier package. Larger chip capacitors, such as the 0.1 F capacitor, can be shared among a few closely spaced active components in the same signal path. A 10 F tantalum capacitor is less critical for high frequency bypassing and, in most cases, only one per board is needed at the supply inputs. The length of the high frequency bypass capacitor leads are most critical. A parasitic inductance in the bypass grounding works against the low impedance created by the bypass capacitor. Place the ground leads of the bypass capacitors at the same physical location. Because load currents flow from the supplies as well, the ground for the load impedance should be at the same physical location as the bypass capacitor grounds. For the larger value capacitors, which are intended to be effective at lower frequencies, the current return path distance is less critical. INPUT CAPACITANCE Along with bypassing and ground, high speed amplifiers can be sensitive to parasitic capacitance between the inputs and ground. A few pF of capacitance reduces the input impedance at high frequencies, in turn increasing the amplifier's gain, causing peaking of the frequency response or even oscillations, if severe enough. It is recommended that the external passive components, which are connected to the input pins, be placed as close as possible to the inputs to avoid parasitic capacitance. The ground and power planes must be kept at a distance of at least 0.05 mm from the input pins on all layers of the board. GROUNDING A ground plane layer is important in densely packed PC boards to spread the current-minimizing parasitic inductances. However, an understanding of where the current flows in a circuit is critical to implementing effective high speed circuit design. The length of the current path is directly proportional to the magnitude of parasitic inductances and thus the high frequency impedance of the path. High speed currents in an inductive ground return create an unwanted voltage noise. INPUT-TO-OUTPUT COUPLING The input and output signal traces should not be parallel to minimize capacitive coupling between the inputs and output and to avoid any positive feedback. Rev. B | Page 13 of 20 A8091/AD8092 DRIVING CAPACITIVE LOADS A highly capacitive load reacts with the output of the amplifiers, causing a loss in phase margin and subsequent peaking or even oscillation, as shown in Figure 29 and Figure 30. There are two methods to effectively minimize its effect. * * 10000 VS = 5V 30% 1000 OVERSHOOT RS = 3 CAPACITIVE LOAD (pF) Put a small value resistor in series with the output to isolate the load capacitor from the amplifier's output stage. Increase the phase margin with higher noise gains or by adding a pole with a parallel resistor and capacitor from -IN to the output. 8 6 4 2 100 RS = 0 RG 10 VIN 100mV STEP 50 1 1 2 3 ACL (V/V) 4 RF RS VOUT 02859-031 CL 5 6 Figure 31. Capacitive Load Drive vs. Closed-Loop Gain GAIN (dB) 0 -2 -4 -6 -8 -10 -12 0.1 VS = 5V G = +1 RL = 2k CL = 50pF VO = 200mV p-p 1 10 FREQUENCY (MHz) 100 500 OVERDRIVE RECOVERY Overdrive of an amplifier occurs when the output and/or input range is exceeded. The amplifier must recover from this overdrive condition. The AD8091/AD8092 recover within 60 ns from negative overdrive and within 45 ns from positive overdrive, as shown in Figure 32. VS = 5V G = +5 RF = 2k RL = 2k Figure 29. Closed-Loop Frequency Response: CL = 50 pF VS = 5V G = +1 RL = 2k CL = 50pF 2.60V 2.55V 2.50V 02859-029 INPUT 1V/DIV OUTPUT 2V/DIV V/DIV AS SHOWN 100ns 2.40V Figure 32. Overdrive Recovery 02859-030 50mV 100ns ACTIVE FILTERS Active filters at higher frequencies require wider bandwidth op amps to work effectively. Excessive phase shift produced by lower frequency op amps can significantly impact active filter performance. Figure 33 shows an example of a 2 MHz biquad bandwidth filter that uses three op amps. Such circuits are sometimes used in medical ultrasound systems to lower the noise bandwidth of the analog signal before A/D conversion. Note that the unused amplifiers' inputs should be tied to ground. Figure 30. 200 mV Step Response: CL = 50 pF As the closed-loop gain is increased, the larger phase margin allows for large capacitor loads with less peaking. Adding a low value resistor in series with the load at lower gains has the same effect. Figure 31 shows the effect of a series resistor for various voltage gains. For large capacitive loads, the frequency response of the amplifier is dominated by the series resistor and capacitive load. Rev. B | Page 14 of 20 02859-032 2.45V AD8091/AD8092 C1 50pF R2 2k VIN R1 3k 2 3 5 R3 1 2k R6 1k VIDEO WITH SYNC VIDEO WITHOUT SYNC R4 2k 6 7 R5 2k C2 50pF 2 6 3 02859-033 VBLANK GROUND +0.4V GROUND 3V OR 5V 0.1F VIN 3 7 AD8092 VOUT AD8092 + AD8091 10F TO A/D 100 Figure 33. 2 MHz Biquad Band-Pass Filter AD8091 2 4 6 The frequency response of the circuit is shown in Figure 34. 0 R2 1k R1 1k -10 +0.8V (OR 2 x VBLANK) Figure 35. Sync Stripper GAIN (dB) -20 -30 The video signal plus sync is applied to the noninverting input with the proper termination. The amplifier gain is set equal to 2 via the two 1 k resistors in the feedback circuit. A bias voltage must be applied to R1 for the input signal to have the sync pulses stripped at the proper level. 02859-034 -40 10k 100k 1M FREQUENCY (Hz) 10M 100M Figure 34. Frequency Response of 2 MHz Band-Pass Biquad Filter SYNC STRIPPER Synchronizing pulses are sometimes carried on video signals so as not to require a separate channel to carry the synchronizing information. However, for some functions, such as A/D conversion, it is not desirable to have the sync pulses on the video signal. These pulses reduce the dynamic range of the video signal and do not provide any useful information for such a function. A sync stripper removes the synchronizing pulses from a video signal while passing all the useful video information. Figure 35 shows a practical single-supply circuit that uses only a single AD8091. It is capable of directly driving a reverse terminated video line. The blanking level of the input video pulse is the desired place to remove the sync information. The amplifier multiplies this level by 2. This level must be at ground at the output in order for the sync stripping action to take place. Because the gain of the amplifier from the input of R1 to the output is -1, a voltage equal to 2 x VBLANK must be applied to make the blanking level come out at ground. SINGLE-SUPPLY COMPOSITE VIDEO LINE DRIVER Many composite video signals have their blanking level at ground and have video information that is both positive and negative. Such signals require dual-supply amplifiers to pass them. However, by ac level-shifting, a single-supply amplifier can be used to pass these signals. The following complications may arise from such techniques. Signals of bounded peak-to-peak amplitude that vary in duty cycle require larger dynamic swing capacity than their (bounded) peak-to-peak amplitude after they are ac-coupled. As a worst case, the dynamic signal swing approaches twice the peak-to-peak value. One of two conditions that define the maximum dynamic swing requirements is a signal that is mostly low but goes high with a duty cycle that is a small fraction of a percent. The opposite condition defines the second condition. The worst case of composite video is not quite this demanding. One bounding condition is a signal that is mostly black for an entire frame but has a white (full amplitude) minimum width spike at least once in a frame. Rev. B | Page 15 of 20 02859-035 A8091/AD8092 The other extreme is a full white video signal. The blanking intervals and sync tips of such a signal have negative-going excursions in compliance with the composite video specifications. The combination of horizontal and vertical blanking intervals limit such a signal to being at the highest (white) level for a maximum of about 75% of the time. As a result of the duty cycles between the two extremes, a 1 V pp composite video signal that is multiplied by a gain of 2 requires about 3.2 V p-p of dynamic voltage swing at the output for an op amp to pass a composite video signal of arbitrary varying duty cycle without distortion. Some circuits use a sync tip clamp to hold the sync tips at a relatively constant level to lower the amount of dynamic signal swing required. However, these circuits can have artifacts like sync tip compression unless they are driven by a source with a very low output impedance. The AD8091/AD8092 have adequate signal swing when running on a single 5 V supply to handle an ac-coupled composite video signal. The input to the circuit in Figure 36 is a standard composite (1 V p-p) video signal that has the blanking level at ground. The input network level shifts the video signal by means of ac coupling. The noninverting input of the op amp is biased to half of the supply voltage. 5V 4.99k 4.99k COMPOSITE VIDEO IN 47F + RT 75 10k 2 + 10F 0.1F 3 7 + 10F 1000F + RBT 75 RL 75 VOUT AD8091 4 6 RF 1k RG 1k 220F 0.1F Figure 36. Single-Supply Composite Video Line Driver The feedback circuit provides unity gain for the dc biasing of the input and provides a gain of 2 for any signals that are in the video bandwidth. The output is ac-coupled and terminated to drive the line. The capacitor values were selected for providing minimum tilt or field time distortion of the video signal. These values would be required for video that is considered to be studio or broadcast quality. However, if a lower consumer grade of video, sometimes referred to as consumer video, is all that is desired, the values and the cost of the capacitors can be reduced by as much as a factor of 5 with minimum visible degradation in the picture. Rev. B | Page 16 of 20 02859-036 AD8091/AD8092 OUTLINE DIMENSIONS 5.00 (0.1968) 4.80 (0.1890) 8 5 8 3.00 BSC 4.00 (0.1574) 3.80 (0.1497) 1 6.20 (0.2440) 3.00 BSC 5 4 5.80 (0.2284) 1 4.90 BSC 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) 1.75 (0.0688) 1.35 (0.0532) 0.50 (0.0196) x 45 0.25 (0.0099) PIN 1 0.65 BSC 1.10 MAX 8 0 0.80 0.60 0.40 0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE 8 0.25 (0.0098) 0 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067) 0.15 0.00 0.38 0.22 COPLANARITY 0.10 COMPLIANT TO JEDEC STANDARDS MS-012-AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN 0.23 0.08 SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 37. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) Figure 38. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters 2.90 BSC 5 4 1.60 BSC 1 2.80 BSC 2 3 PIN 1 0.95 BSC 1.30 1.15 0.90 1.90 BSC 1.45 MAX 0.22 0.08 10 5 0 0.60 0.45 0.30 0.15 MAX 0.50 0.30 SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-178AA Figure 39. 5-Lead Small Outline Transistor Package [SOT-23] (RT-5) Dimensions shown in millimeters Rev. B | Page 17 of 20 A8091/AD8092 ORDERING GUIDE Model AD8091AR AD8091AR-REEL AD8091AR-REEL7 AD8091ARZ1 AD8091ARZ-REEL1 AD8091ARZ-REEL71 AD8091ART-R2 AD8091ART-REEL AD8091ART-REEL7 AD8091ARTZ-R21 AD8091ARTZ-R71 AD8091ARTZ-RL1 AD8092AR AD8092AR-REEL AD8092AR-REEL7 AD8092ARZ1 AD8092ARZ-REEL1 AD8092ARZ-REEL71 AD8092ARM AD8092ARM-REEL AD8092ARM-REEL7 AD8092ARMZ1 AD8092ARMZ-REEL1 AD8092ARMZ-REEL71 1 Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package Description 8-Lead SOIC 8-Lead SOIC, 13" Tape and Reel 8-Lead SOIC, 7" Tape and Reel 8-Lead SOIC 8-Lead SOIC, 13" Tape and Reel 8-Lead SOIC, 7" Tape and Reel 5-Lead SOT-23 5-Lead SOT-23, 13" Tape and Reel 5-Lead SOT-23, 7" Tape and Reel 5-Lead SOT-23 5-Lead SOT-23, 7" Tape and Reel 5-Lead SOT-23, 13" Tape and Reel 8-Lead SOIC 8-Lead SOIC, 13" Tape and Reel 8-Lead SOIC, 7" Tape and Reel 8-Lead SOIC 8-Lead SOIC, 13" Tape and Reel 8-Lead SOIC, 7" Tape and Reel 8-Lead MSOP 8-Lead MSOP, 13" Tape and Reel 8-Lead MSOP, 7" Tape and Reel 8-Lead MSOP 8-Lead MSOP, 13" Tape and Reel 8-Lead MSOP, 7" Tape and Reel Package Outline R-8 R-8 R-8 R-8 R-8 R-8 RT-5 RT-5 RT-5 RT-5 RT-5 RT-5 R-8 R-8 R-8 R-8 R-8 R-8 RM-8 RM-8 RM-8 RM-8 RM-8 RM-8 Branding Information HVA HVA HVA HVA# HVA# HVA# HWA HWA HWA HWA# HWA# HWA# Z = Pb-free part. # denotes lead-free, may be top or bottom marked. Rev. B | Page 18 of 20 AD8091/AD8092 NOTES Rev. B | Page 19 of 20 A8091/AD8092 NOTES (c) 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C02859-0-3/05(B) Rev. B | Page 20 of 20 |
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