ADA4855-3YCPZ-R2

Single Supply, High Speed, Rail-to-Rail Output, Triple Op Amp ADA4855-3 FEATURES Voltage feedback architecture Rail-to-rail output swing: 0.1 V to 4.9 V High speed amplifiers 410 MHz, −3 dB bandwidth, G = 1 210 MHz, −3 dB bandwidth, G = 2 Slew rate: 870 V/μs 53 MHz, 0.1 dB large signal flatness 5.3 ns settling time to 0.1% with 2 V step High input common-mode voltage range −VS − 0.2 V to +VS − 1 V Supply range: 3 V to 5.5 V Differential gain error: 0.01% Differential phase error: 0.01° Low power 7.8 mA/amplifier typical supply current Power-down feature Available in 16-lead LFCSP CONNECTION DIAGRAM OUT1 +IN1 –IN1 16 15 14 13 –VS NC +IN2 NC PD 1 2 3 4 12 +VS ADA4855-3 11 OUT2 10 –IN2 9 +VS 5 +IN3 6 –IN3 7 OUT3 8 –VS NOTES 1. NC = NO CONNECT. 2. EXPOSED PAD CONNECTED TO –VS. Figure 1. APPLICATIONS Professional video Consumer video Imaging Instrumentation Base stations Active filters GENERAL DESCRIPTION The ADA4855-3 (triple) is a single-supply, rail-to-rail output operational amplifier. It provides excellent high speed performance with 410 MHz, −3 dB bandwidth and a slew rate of 870 V/μs. It has a wide input common-mode voltage range that extends from 0.2 V below ground to 1 V below the positive rail.In addition, the output voltage swings within 100 mV of either supply rail, making this rail-to-rail operational amplifier easy to use on singlesupply voltages as low as 3.3 V. The ADA4855-3 offers a typical low power of 7.8 mA per amplifier and is capable of delivering up to 57 mA of load current. It also features a power-down function for power sensitive applications that reduces the supply current down to 1 mA. The ADA4855-3 is available in a 16-lead LFCSP and is designed to work over the extended industrial temperature range of −40°C to +105°C. NORMALIZED CLOSED-LOOP GAIN (dB) 1 0 G=1 –1 G=2 –2 –3 –4 –5 –6 1 100 10 FREQUENCY (MHz) 1000 G=5 07685-001 Figure 2. Frequency Response 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. 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 ©2008 Analog Devices, Inc. All rights reserved. 07685-004 ADA4855-3 TABLE OF CONTENTS Features .............................................................................................. 1  Applications ....................................................................................... 1  Connection Diagram ....................................................................... 1  General Description ......................................................................... 1  Revision History ............................................................................... 2  Specifications..................................................................................... 3  5 V Operation ............................................................................... 3  3.3 V Operation ............................................................................ 4  Absolute Maximum Ratings............................................................ 5  Thermal Resistance ...................................................................... 5  Maximum Power Dissipation ..................................................... 5  ESD Caution .................................................................................. 5  Pin Configuration and Function Descriptions ............................. 6  Typical Performance Characteristics ............................................. 7  Test Circuits ..................................................................................... 13  Theory of Operation ...................................................................... 14  Applications Information .............................................................. 15  Gain Configurations .................................................................. 15  20 MHz Active Low-Pass Filter ................................................ 15  RGB Video Driver ...................................................................... 16  Driving Multiple Video Loads .................................................. 16  PD (Power-Down) Pin .............................................................. 16  Single-Supply Operation ........................................................... 17  Power Supply Bypassing ............................................................ 17  Layout .......................................................................................... 17  Outline Dimensions ....................................................................... 18  Ordering Guide .......................................................................... 18  REVISION HISTORY 11/08—Revision 0: Initial Version Rev. 0 | Page 2 of 20 ADA4855-3 SPECIFICATIONS 5 V OPERATION TA = 25°C, VS = 5 V, G = 1, RL = 150 Ω, unless otherwise noted. Table 1. Parameter DYNAMIC PERFORMANCE −3 dB Bandwidth Test Conditions VO = 0.1 V p-p VO = 2 V p-p VO = 0.1 V p-p, G = 2 VO = 2 V p-p, G = 2 VO = 2 V p-p VO = 2 V p-p, G = 2 VO = 2 V step VO = 2 V step (rise/fall) VO = 2 V step (rise/fall), G = 2 fC = 5 MHz, VO = 2 V p-p, RL = 1 kΩ fC = 20 MHz, VO = 2 V p-p, RL = 1 kΩ f = 5 MHz, G = 2 f = 100 kHz f = 100 kHz G=2 G=2 Min Typ 410 200 210 120 53 50 870 5.3/9.5 7.4/7 −84/−105 −60/−66 −90 6.8 2 0.01 0.01 1.3 5.5 −3.8 ±0.05 92 6.4 0.5 −VS − 0.2 VCM = –0.2 V to +4 V 94 0.1 to 4.9 57 78 1.2 0.3 −125 +VS − 1.25 3 7.8 1.1 96 5.5 +VS − 1 3 Max Unit MHz MHz MHz MHz MHz MHz V/μs ns ns dBc dBc dBc nV/√Hz pA/√Hz % Degrees mV μV/°C μA μA dB MΩ pF V dB V mA ns μs μA μA V V mA mA dB Bandwidth for 0.1 dB Flatness Slew Rate Settling Time to 0.1% NOISE/DISTORTION PERFORMANCE Harmonic Distortion (HD2/HD3) Crosstalk, Output to Output Input Voltage Noise Input Current Noise Differential Gain Error Differential Phase Error DC PERFORMANCE Input Offset Voltage Input Offset Voltage Drift Input Bias Current Input Offset Current Open-Loop Gain INPUT CHARACTERISTICS Input Resistance Input Capacitance Input Common-Mode Voltage Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing Linear Output Current per Amplifier POWER-DOWN Turn-On Time Turn-Off Time Bias Current Turn-On Voltage POWER SUPPLY Operating Range Quiescent Current per Amplifier Supply Current When Powered Down Power Supply Rejection Ratio VO = 0.5 V to 4.5 V HD2 ≤ −60 dBc, RL = 10 Ω On Off ∆VS = 4.5 V to 5.5 V Rev. 0 | Page 3 of 20 ADA4855-3 3.3 V OPERATION TA = 25°C, VS = 3.3 V, G = 1, RL = 150 Ω, unless otherwise noted. Table 2. Parameter DYNAMIC PERFORMANCE −3 dB Bandwidth Test Conditions VO = 0.1 V p-p VO = 1.4 V p-p VO = 0.1 V p-p, G = 2 VO = 2 V p-p, G = 2 VO = 1.4 V p-p, G = 2 VO = 2 V step, G = 2 VO = 2 V step (rise/fall), G = 2 fC = 5 MHz, VO = 2 V p-p, RL = 1 kΩ fC = 20 MHz, VO = 2 V p-p, RL = 1 kΩ f = 5 MHz, G = 2 f = 100 kHz f = 100 kHz G=2 G=2 Min Typ 430 210 210 125 55 870 7.4/7.1 −76/−76 −68/−75 −88 6.8 2 0.01 0.01 1.3 5.5 −3.8 0.05 92 6.4 0.5 −VS − 0.2 VCM = –0.2 V to +3.2 V 94 0.1 to 3.22 40 78 1.2 +VS − 1.25 3 7.5 0.95 94 5.5 +VS − 1 Max Unit MHz MHz MHz MHz MHz V/μs ns dBc dBc dBc nV/√Hz pA/√Hz % Degrees mV μV/°C μA μA dB MΩ pF V dB V mA ns μs V V mA mA dB Bandwidth for 0.1 dB Flatness Slew Rate Settling Time to 0.1% NOISE/DISTORTION PERFORMANCE Harmonic Distortion (HD2/HD3) Crosstalk, Output to Output Input Voltage Noise Input Current Noise Differential Gain Error Differential Phase Error DC PERFORMANCE Input Offset Voltage Input Offset Voltage Drift Input Bias Current Input Offset Current Open-Loop Gain INPUT CHARACTERISTICS Input Resistance Input Capacitance Input Common-Mode Voltage Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing Linear Output Current per Amplifier POWER-DOWN Turn-On Time Turn-Off Time Turn-On Voltage POWER SUPPLY Operating Range Quiescent Current per Amplifier Supply Current When Powered Down Power Supply Rejection Ratio VO = 0.5 V to 4.5 V HD2 ≤ −60 dBc, RL = 10 Ω ∆VS = 2.97 V to 3.63 V Rev. 0 | Page 4 of 20 ADA4855-3 ABSOLUTE MAXIMUM RATINGS Table 3. Parameter Supply Voltage Internal Power Dissipation1 Common-Mode Input Voltage Differential Input Voltage Output Short-Circuit Duration Storage Temperature Range Operating Temperature Range Lead Temperature (Soldering, 10 sec) 1 MAXIMUM POWER DISSIPATION Rating 6V See Figure 3 (−VS − 0.2 V) to (+VS − 1 V) ±VS Observe power curves −65°C to +125°C −40°C to +105°C 300°C The maximum power that can be safely dissipated by the ADA4855-3 is limited by the associated rise in junction temperature. The maximum safe junction temperature for plastic encapsulated devices is determined by the glass transition temperature of the plastic, approximately 150°C. Temporarily exceeding this limit may cause a shift in parametric performance due to a change in the stresses exerted on the die by the package. Exceeding a junction temperature of 175°C for an extended period can result in device failure. To ensure proper operation, it is necessary to observe the maximum power derating curves. 3.0 MAXIMUM POWER DISSIPATION (W) Specification is for device in free air. 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. 2.5 2.0 1.5 THERMAL RESISTANCE θJA is specified for the worst-case conditions, that is, θJA is specified for a device soldered in a circuit board for surface-mount packages. Table 4. Package Type 16-Lead LFCSP θJA 67 θJC 17.5 Unit °C/W 1.0 0.5 07685-103 0 10 20 30 40 50 60 70 80 –40 –30 –20 –10 90 AMBIENT TEMPERATURE (°C) Figure 3. Maximum Power Dissipation vs. Ambient Temperature ESD CAUTION Rev. 0 | Page 5 of 20 100 0 ADA4855-3 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 16 +IN1 15 –IN1 14 OUT1 13 –VS NC 1 +IN2 2 NC 3 PD 4 12 +VS ADA4855-3 TOP VIEW (Not to Scale) 11 OUT2 10 –IN2 9 +VS NOTES 1. NC = NO CONNECT. 2. EXPOSED PAD CONNECTED TO –VS. OUT3 7 +IN3 5 –IN3 6 –VS 8 Figure 4. Pin Configuration Table 5. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 (EPAD) Mnemonic NC +IN2 NC PD +IN3 −IN3 OUT3 −VS +VS −IN2 OUT2 +VS −VS OUT1 −IN1 +IN1 Exposed Pad (EPAD) Description No Connect. Noninverting Input 2. No Connect. Power Down. Noninverting Input 3. Inverting Input 3. Output 3. Negative Supply. Positive Supply. Inverting Input 2. Output 2. Positive Supply. Negative Supply. Output 1. Inverting Input 1. Noninverting Input 1. The exposed pad must be connected to −VS. Rev. 0 | Page 6 of 20 07685-003 ADA4855-3 TYPICAL PERFORMANCE CHARACTERISTICS T = 25°C, VS = 5V, G = 1, RF = 1 kΩ for G > 1, RL = 150 Ω, small signal VOUT = 100 mV p-p, and large signal VOUT = 2 V p-p, unless otherwise noted. 1 0 G=1 –1 G=2 –2 –3 –4 –5 –6 1 10 100 FREQUENCY (MHz) 1000 G=5 NORMALIZED CLOSED-LOOP GAIN (dB) NORMALIZED CLOSED-LOOP GAIN (dB) 1 0 G=1 –1 –2 –3 –4 –5 –6 1 100 10 FREQUENCY (MHz) 1000 G=5 G=2 07685-004 Figure 5. Small Signal Frequency Response vs. Gain 1 0 –1 –2 –3 –4 –5 VS = 3.3V 07685-005 Figure 8. Large Signal Frequency Response vs. Gain 1 G=1 NORMALIZED CLOSED-LOOP GAIN (dB) NORMALIZED CLOSED-LOOP GAIN (dB) 0 –1 –2 –3 –4 –5 VS = 3.3V –6 1 G=2 VOUT = 2V p-p G=1 VOUT = 1.4V p-p G=5 G=2 G=5 VOUT = 2V p-p 1 10 100 FREQUENCY (MHz) 1000 100 10 FREQUENCY (MHz) 1000 Figure 6. Small Signal Frequency Response vs. Gain 1 0 CLOSED-LOOP GAIN (dB) 1 Figure 9. Large Signal Frequency Response vs. Gain RL = 1kΩ CF = 4.4pF CF = 6.6pF 0 –1 RL = 150Ω –2 –3 –4 –5 –6 1 10 100 FREQUENCY (MHz) 1000 CLOSED-LOOP GAIN (dB) –1 –2 –3 –4 –5 –6 1 CF = 2.2pF 07685-006 100 10 FREQUENCY (MHz) 1000 Figure 7. Small Signal Frequency Response vs. Load Figure 10. Small Signal Frequency Response vs. Capacitive Load Rev. 0 | Page 7 of 20 07685-009 07685-008 –6 07685-007 ADA4855-3 0.2 0.1 6.2 6.1 VS = 3.3V, VOUT = 1.4V p-p CLOSED-LOOP GAIN (dB) VS = 5V CLOSED-LOOP GAIN (dB) 0 –0.1 VS = 5V, VOUT = 2V p-p –0.2 –0.3 –0.4 –0.5 6.0 VS = 3.3V 5.9 5.8 5.7 5.6 G=2 5.5 1 10 100 FREQUENCY (MHz) 07685-037 1 10 100 FREQUENCY (MHz) 1000 1000 Figure 11. 0.1 dB Flatness vs. Supply Voltage 1 0 Figure 14. 0.1 dB Flatness vs. Supply Voltage 100 0 TA = +85°C TA = +105°C TA = –40°C TA = +25°C 75 PHASE –50 CLOSED-LOOP GAIN (dB) –1 –2 –3 –4 –5 –6 GAIN 25 –150 0 –200 –25 07685-038 –250 07685-035 1 10 100 FREQUENCY (MHz) 1000 –50 10 100 1k 10k 100k 1M 10M 100M 1G –300 10G FREQUENCY (Hz) Figure 12. Small Signal Frequency Response vs. Temperature –50 –55 –60 DISTORTION (dBc) Figure 15. Open-Loop Gain and Phase vs. Frequency –50 –60 –70 VOUT = 1V p-p RL = 1kΩ VOUT = 1V p-p VS = 3.3V RL = 1kΩ –65 –70 –75 –80 –85 –90 0.1 HD2 HD3 DISTORTION (dBc) –80 –90 –100 –110 HD2 07685-014 1 FREQUENCY (MHz) 10 40 –130 0.1 1 FREQUENCY (MHz) 10 40 Figure 13. Harmonic Distortion vs. Frequency Figure 16. Harmonic Distortion vs. Frequency Rev. 0 | Page 8 of 20 07685-011 –120 HD3 PHASE (Degrees) 50 –100 GAIN (dB) 07685-040 ADA4855-3 0 –40 –50 –60 –20 FORWARD ISOLATION (dB) CROSSTALK (dB) –40 OUT3 OUT1 –80 OUT2 07685-012 IN2, IN3, OUT1 –70 –80 –90 –100 IN1, IN2, OUT3 –60 IN1, IN3, OUT2 –100 –120 0.1 1 10 FREQUENCY (MHz) 100 1000 –120 1 10 100 1000 FREQUENCY (MHz) Figure 17. Forward Isolation vs. Frequency 0 –10 –20 –30 PSRR (dB) Figure 20. Crosstalk vs. Frequency –30 –40 –50 –40 –50 –60 –70 –80 07685-013 CMRR (dB) –60 –70 –80 –90 –100 0.01 –PSRR +PSRR –90 –100 0.01 0.1 1 10 FREQUENCY (MHz) 100 0.1 1 10 FREQUENCY (MHz) 100 Figure 18. Power Supply Rejection Ratio (PSRR) vs. Frequency 100 Figure 21. Common-Mode Rejection Ratio (CMRR) vs. Frequency 100 CURRENT NOISE (pA/√Hz) VOLTAGE NOISE (nV/√Hz) VS = 5V VS = 3.3V 10 10 1 10 100 1k 10k 100k FREQUENCY (Hz) 1M 07685-020 1 10M 10 100 1k 10k FREQUENCY (Hz) 100k 1M Figure 19. Input Current Noise vs. Frequency Figure 22. Input Voltage Noise vs. Frequency Rev. 0 | Page 9 of 20 07685-017 07685-016 07685-015 –110 ADA4855-3 0.08 0.06 0.04 0.02 0 –0.02 –0.04 VS = 3.3V VS = 5V 1.5 CL = 2.2pF CL = 4.4pF CL = 6.6pF 1.0 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 0.5 0 –0.5 –1.0 07685-018 –0.08 TIME (10ns/DIV) –1.5 TIME (10ns/DIV) Figure 23. Small Signal Transient Response vs. Supply Voltage 0.08 0.06 0.04 0.02 0 –0.02 –0.04 07685-019 Figure 26. Large Signal Transient Response vs. Capacitive Load 0.08 0.06 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) CL = 2.2pF CL = 4.4pF CL = 6.6pF 0.04 0.02 0 –0.02 –0.04 CL = 2.2pF CL = 4.4pF CL = 6.6pF VS = 3.3V –0.08 TIME (10ns/DIV) –0.08 TIME (10ns/DIV) Figure 24. Small Signal Transient Response vs. Capacitive Load 1.5 Figure 27. Small Signal Transient Response vs. Capacitive Load 23.7 RL = 150Ω RL = 1kΩ 1.0 QUIESCENT CURRENT (mA) OUTPUT VOLTAGE (V) 23.2 0.5 0 22.7 –0.5 22.2 –1.0 07685-021 TIME (10ns/DIV) SUPPLY VOLTAGE (V) Figure 25. Large Signal Transient Response vs. Load Resistance Figure 28. Quiescent Current vs. Supply Voltage Rev. 0 | Page 10 of 20 07685-029 –1.5 21.7 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 07685-023 –0.06 –0.06 07685-022 –0.06 ADA4855-3 4 3 2 1 2 × VIN 2.5 2.0 1.5 2 × VIN VOUT VOLTAGE (V) 1.0 0.5 0 –0.5 –1.0 –1.5 07685-025 VOUT VOLTAGE (V) 0 –1 –2 G=2 –4 TIME (50ns/DIV) –2.0 –2.5 TIME (50ns/DIV) Figure 29. Output Overdrive Recovery 0.6 2.0 Figure 32. Output Overdrive Recovery 3 VPD VOUT VOUT = 1V p-p VS = 3.3V 0.4 OUTPUT VOLTAGE (V) 0.2 OUTPUT VOLTAGE (V) 1.0 1 0.5 0 –0.5 –1.0 0 0 –0.2 –1 –0.4 07685-026 –2 07685-129 07685-027 –1.5 –2.0 –3 –0.6 TIME (10ns/DIV) TIME (1µs/DIV) Figure 30. Large Signal Transient Response vs. Capacitive Load 0.5 0.4 0.3 SETTLING TIME (%) 0.5 0.4 0.3 Figure 33. Turn-On/Turn-Off Time INPUT SETTLING TIME (%) 0.2 0.1 0 –0.1 –0.2 –0.3 INPUT 0.2 0.1 0 –0.1 –0.2 –0.3 ERROR ERROR 07685-024 –0.4 –0.5 TIME (2ns/DIV) –0.4 –0.5 VS = 3.3V TIME (2ns/DIV) Figure 31. Settling Time Figure 34. Settling Time Rev. 0 | Page 11 of 20 POWER-DOWN VOLTAGE (V) CL = 2.2pF CL = 4.4pF CL = 6.6pF 1.5 2 07685-028 –3 G=2 VIN = 3.3V ADA4855-3 0 100 –10 –20 –30 OUTPUT IMPEDANCE (Ω) OFFSET VOLTAGE (mV) 10 VS = 3.3V 1 –40 VS = 5V –50 07685-031 0.1 07685-036 –60 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 COMMON-MODE VOLTAGE (V) 4.5 5.0 0.01 0.1 1 10 100 FREQUENCY (MHz) 1000 Figure 35. Input Offset Voltage vs. Common-Mode Voltage 23.6 23.4 QUIESCENT CURRENT (mA) 23.2 23.0 22.8 22.6 22.4 22.2 22.0 07685-032 Figure 38. Output Impedance vs. Frequency 5.00 VS = 5V 4.95 SATURATION VOLTAGE (mV) 4.90 4.85 4.80 4.75 4.70 07685-039 VS = 3.3V 4.65 4.60 0.01 21.8 –40 –25 –10 5 20 35 50 65 80 95 110 125 0.1 TEMPERATURE (°C) 1 LOAD CURRENT (mA) 10 100 Figure 36. Quiescent Current vs. Temperature 2.4 2.2 Figure 39. Output Saturation Voltage vs. Load Current OFFSET VOLTAGE (mV) 2.0 1.8 1.6 1.4 1.2 1.0 –40 –20 0 20 40 60 TEMPERATURE (°C) 80 100 Figure 37. Offset Drift vs. Temperature 07685-034 Rev. 0 | Page 12 of 20 ADA4855-3 TEST CIRCUITS +VS +VS 10µF + 10µF + 1kΩ 0.1µF VIN 49.9Ω 10µF + 0.1µF VOUT RL VIN 1kΩ 1kΩ 53.6Ω 07685-041 0.1µF 0.1µF VOUT 1kΩ 10µF + 0.1µF –VS RL –VS Figure 40. Noninverting Load Configuration +VS AC Figure 43. Common-Mode Rejection +VS 10µF 49.9Ω 0.1µF VOUT RL 10µF 49.9Ω 07685-042 VOUT RL AC –VS 07685-045 + 0.1µF –VS Figure 41. Positive Power Supply Rejection +VS 10µF Figure 44. Negative Power Supply Rejection +VS 10µF RG RF 0.1µF 0.1µF VOUT 49.9Ω 10µF CL RL RG RF 0.1µF 0.1µF VOUT 49.9Ω 10µF RL VIN VIN + 07685-043 –VS –VS Figure 42. Typical Capacitive Load Configuration Figure 45. Typical Noninverting Gain Configuration Rev. 0 | Page 13 of 20 07685-046 0.1µF + 0.1µF 07685-044 0.1µF + + + ADA4855-3 THEORY OF OPERATION The ADA4855 is a voltage feedback op amp that employs a new input stage that achieves a high slew rate while maintaining a wide common-mode input range. The input common-mode range of the ADA4855 extends from 200 mV below the negative rail to 1 V below the positive rail. This feature makes the ADA4855 ideal for single-supply applications. In addition, this new input stage does not sacrifice noise performance for slew rate. At 6.8 nV/√Hz, the ADA4855 is one of the lowest noise rail-torail output video amplifiers in the market. Besides a novel input stage, the ADA4855 employs the Analog Devices, Inc., patented rail-to-rail output stage. This output stage makes efficient use of the power supplies, allowing the op amp to drive up to three video loads to within 350 mV of the positive power rail. In addition, this output stage provides the amplifier with very fast overdrive characteristics, which is an important property in video applications. The ADA4855 comes in a 16-lead LFCSP that has an exposed thermal pad for lower operating temperature. This pad is internally connected to the negative rail. To avoid printed circuit board (PCB) layout problems, the ADA4855 features a new pinout flow that is optimized for video applications. As shown in Figure 4, the noninverting input and output pins of each amplifier are adjacent to each other for ease of layout. The ADA4855 is fabricated in Analog Devices dielectrically isolated eXtra Fast Complementary Bipolar 3 (XFCB3) process, which results in the outstanding speed and dynamic range displayed by the amplifier. +VS C1 +IN Gm1 –IN R Gm2 OUT –VS Figure 46. High Level Design Schematic Rev. 0 | Page 14 of 20 07685-147 C ADA4855-3 APPLICATIONS INFORMATION GAIN CONFIGURATIONS The ADA4855-3 is a single-supply, high speed, voltage feedback amplifier. Table 6 provides a convenient reference for quickly determining the feedback and gain set resistor values and bandwidth for common gain configurations. Table 6. Recommended Values and Frequency Performance1 Gain 1 2 5 1 20 MHz ACTIVE LOW-PASS FILTER The ADA4855-3 triple amplifier lends itself to higher order active filters. Figure 49 shows a 20 MHz, 6-pole, Sallen-Key low-pass filter. R7 1kΩ R8 261Ω RF 0Ω 1 kΩ 1 kΩ RG N/A 1 kΩ 200 Ω −3 dB SS BW (MHz) 200 120 45 Large Signal 0.1 dB Flatness (MHz) 53 50 6 – R1 232Ω R2 1.69kΩ C1 15pF C2 6.6pF U1 OP AMP + OUT1 VIN Conditions: VS = 5 V, TA = 25°C, RL = 150 Ω. R9 1kΩ – R3 309Ω R4 1.87kΩ C3 15pF C4 4.3pF R10 261Ω U2 OP AMP + OUT2 Figure 47 and Figure 48 show the typical noninverting and inverting configurations and recommended bypass capacitor values. +VS 10µF 0.1µF VIN + ADA4855-3 0.1µF – 0.1µF 10µF RF RG –VS VOUT R11 1kΩ – R5 261Ω R6 1.43kΩ C5 33pF 07685-047 R12 261Ω U3 OP AMP + C6 3pF OUT3 VOUT Figure 49. 20 MHz, 6-Pole Low-Pass Filter Figure 47. Noninverting Gain Configuration RF +VS 10µF 0.1µF VIN RG – The filter has a gain of approximately 6 dB and flat frequency response out to 14 MHz. This type of filter is commonly used at the output of a video DAC as a reconstruction filter. The frequency response of the filter is shown in Figure 50. 10 OUT3 0 OUT2 –10 MAGNITUDE (dB) OUT1 ADA4855-3 0.1µF + 0.1µF 10µF –VS VOUT –20 –30 –40 –50 07685-048 –60 07685-050 Figure 48. Inverting Gain Configuration –70 1 10 FREQUENCY (MHz) 100 200 Figure 50. 20 MHz, Low-Pass Filter Frequency Response Rev. 0 | Page 15 of 20 07685-049 ADA4855-3 RGB VIDEO DRIVER Figure 51 shows a typical RGB driver application using dual supplies. The gain of the amplifier is set at +2, where RF = RG = 1 kΩ. The amplifier inputs are terminated with shunt 75 Ω resistors, and the outputs have series 75 Ω resistors for proper video matching. In Figure 51, the PD pin is not shown connected to any signal source for simplicity. If the power-down function is not used, it is recommended that the PD pin be tied to the positive supply or be left floating (not connected). 75Ω VIN (R) 1kΩ 1kΩ 75Ω –VS 0.1µF 0.1µF 1 12 6.5 6.0 5.5 MAGNITUDE (dB) 5.0 4.5 4.0 3.5 3.0 VOUT = 2V p-p G=2 RL = 150Ω RL = 75Ω RL = 50Ω VOUT (R) 2.5 1 10 FREQUENCY (MHz) 100 200 16 15 14 13 +VS VIN (G) 75Ω 2 3 ADA4855-3 11 10 9 75Ω 1kΩ 1kΩ +VS 0.1µF 0.1µF 0.1µF + PD 4 5 6 7 8 VIN (B) 75Ω 1kΩ 1kΩ –VS 75Ω 07685-051 VOUT (B) Figure 51. RGB Video Driver DRIVING MULTIPLE VIDEO LOADS Each amplifier in the ADA4855-3 can drive up to three video loads simultaneously, as shown in Figure 52. When driving three video loads, the ADA4855-3 maintains its excellent performance for 0.1 dB flatness and 3 dB bandwidth. Figure 53 shows the large signal frequency response of the ADA4855-3 with three different load configurations: 150 Ω, 75 Ω and 50 Ω. RF 1kΩ +VS RG 1kΩ 10µF 0.1µF 75Ω 75Ω CABLE VOUT1 75Ω 75Ω 75Ω CABLE 0.1µF 0.1µF 75Ω 10µF 75Ω 75Ω CABLE 75Ω 75Ω – ADA4855-3 + 75Ω CABLE VIN –VS Figure 52. Video Driver Schematic for Triple Video Loads Rev. 0 | Page 16 of 20 07685-052 + 0.1µF 10µF Figure 53. Large Signal Frequency Response vs. Loads PD (POWER-DOWN) PIN VOUT (G) 10µF The ADA4855-3 is equipped with a PD (power-down) pin for all three amplifiers. This allows the user to reduce the quiescent supply current when an amplifier is inactive. The power-down threshold levels are derived from the voltage applied to the +VS pin. When used in single-supply applications, this is especially useful with conventional logic levels. The amplifier is enabled when the voltage applied to the PD pin is greater than +VS − 1.25 V. In a single-supply application, the voltage threshold is typically +3.75 V, and in a ±2.5 V dualsupply application, the voltage threshold is typically +1.25 V. The amplifier is also enabled when the PD pin is left floating (not connected). However, the amplifier is powered down when the voltage on the PD pin is lower than 2.5 V from +VS. If the PD pin is not used, it is best to connect it to the positive supply. Table 7. Power-Down Voltage Control PD Pin Not Active Active 5V >3.75 V 1.25 V 1.75 V