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文档下载 免费文档下载 http://doc.guandang.net/ AD8022ARMZ-REEL7 中文资料 本文档下载自文档下载网,内容可能不完整,您可以点击以下网址继续阅读或下载: http://doc.guandang.net/bbeb08690470a5ac86e08df20.html FEATURES Low power amplifiers provide low noise and low distortion, ideal for xDSL modem receiver Wide supply range: 5 V, ±2.5 V to ±12 V voltage supply Low power consumption: 4.0 mA/Amp Voltage feedback Ease of Use Lower total noise (insignificant input current noise contribution compared to current feedback amps) Low noise and distortion 2.5 nV/√Hz voltage noise @ 100 kHz 1.2 pA/√Hz current noise MTPR 130 MHz bandwidth (?3 dB), G = 1 Settling time to 0.1%, 68 ns 50 V/μs slew rate High output swing: ±10.1 V on ±12 V supply Low offset voltage, 1.5 mV typical APPLICATIONS Receiver for ADSL, VDSL, HDSL, and proprietary xDSL systems 文档下载 免费文档下载 http://doc.guandang.net/ Low noise instrumentation front end Ultrasound preamps Active filters 16-bit ADC buffers GENERAL DESCRIPTIONS The AD8022 consists of two low noise, high speed, voltage feedback amplifiers. Each amplifier consumes only 4.0 mA of quiescent chttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlurrent, yet has only 2.5 nV/√Hz of voltage noise. These dual amplifiers provide wideband, low distortion performance, with high output current optimized for stability when driving capacitive loads. Manufactured on ADI’s high voltage generation of XFCB bipolar process, the AD8022 operates on a wide range of supply voltages. The AD8022 is available in both an 8-lead MSOP and an 8-lead SOIC. Fast over voltage recovery and wide bandwidth make the AD8022 ideal as the receive channel front end to an ADSL, VDSL, or proprietary xDSL transceiver design. In an xDSL line interface circuit, the AD8022’s op amps can be configured as the differential receiver from the line transformer or as independent active filters. Rev. B nformation 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 http://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlother or 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 文档下载 免费文档下载 http://doc.guandang.net/ respective owners. Dual High Speed,Low Noise Op Amp AD8022 FUNCTIONAL BLOCK DIAGRAM OUT1 VS–IN1OUT2 IN1–IN21 0–VS IN2 0-35010 Figure 1. 100 ) /Vn ,10 /A p(2 00-350110FREQUENCY (Hz) 文档下载 免费文档下载 http://doc.guandang.net/ Figure 2. Current and Voltage Noise vs. Frequency 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?2005 Analog Devices, Inc. All rights reserved. AD8022 TABLE OF CONTENTS Specifications..........................................http://doc.guandang.net/ bbeb08690470a5ac86e08df20.html...........................................3 Absolute Maximum Ratings............................................................5 Maximum Power Dissipation.....................................................5 ESD Caution......................................................................... .........5 Typical Characteristics.............................................6 Performance Theory of Operation......................................................................1 2 Applications.................................................................... .................13 DMT Modulation and Multitone Power Ratio (MTPR).......13 Channel Capacity and SNR.......................................................13 Decoupling..................................................13 Power Supply and Layout Considerations...............................................................15 文档下载 免费文档下载 http://doc.guandang.net/ Outline Dimensions.................................http://doc.guandang.net/bbeb08690470a 5ac86e08df20.html......................................16 Ordering Guide..........................................................................1 6 REVISION HISTORY 5/05—Rev. A to Rev. B Changes to Format.............................................................Universal Deleted Evaluation Boards Section..............................................14 Deleted Generating DMT Section................................................14 Changes to Ordering Guide..........................................................16 Updated Outline Dimensions.......................................................16 9/02—Rev. 0 to Rev. A Changes to Features........................................................................ ..1 Changes to Applications...................................................................1 Changes to Product Description.....................................................1 Changes Funchttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmltional Diagram..........................................1 Changes to Block to Figure 1...........................................................................1 Changes to Specifications 文档下载 免费文档下载 http://doc.guandang.net/ Table......................................................2 Edits to TPCs 1, 2, 3, 6......................................................................5 New TPCs 7, 8............................................................................... .....6 Edits to TPCs 16, 17, 18....................................................................7 Edits to TPC 19.............................................................................. ....8 Edits to TPC 28.............................................................................. ....9 Edits to Figure 3............................................................................... 11 Edits to Figure 6............................................................................... 14 Updated Outlinhttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmle Dimensions........................................................16 Rev. B | Page 2 of 16 AD8022 SPECIFICATIONS At 25°C, VS = ±12 V, RL = 500 Ω, G = 1, TMIN = –40°C, TMAX = 85°C, unless otherwise noted. Table 1. Unit DYNAMIC PERFORMANCE ?3 dB Small Signal Bandwidth VOUT = 50 mV p-p 110 130 MHz Bandwidth for 0.1 dB Flatness VOUT = 50 mV p-p 25 MHz Large Signal 文档下载 免费文档下载 http://doc.guandang.net/ Bandwidth1VOUT = 4 V p-p 4 MHz Slew Rate VOUT = 2 V p-p, G = 2 40 50 and Fall Time VOUT = 2 V p-p, G = 2 30 V/μs Rise ns Settling Time 0.1% VOUT = 2 V p-p 62 ns 200 ns Overdrive Recovery Time VOUT = 150% of max output voltage, G = 2 NOISE/DISTORTION PERFORMANCE OUT = 2 V p-p dBc Third Harmonic fC = 1 MHz ?100 differential 26 kHz to 132 kHz Second Harmonic fC = 1 MHz dBc Multitone Input Power Ratio2G = ?67.2 dBc 144 kHz to 1.1 MHz ?66 ?95 7 dBc Voltahttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlge Noise (RTI) f = 100 kHz 2.5 nV/√Hz Input Current Noise f = 100 kHz Input Offset Voltage ?1.5 ±6 mV TMIN to TMAX nA Input Bias Current 2.5 5.0 μA TMIN to TMAX CHARACTERISTICS 0.7 pF Input Common-Mode Voltage Range ±10.1 error = 1% V μA Open-Loop Gain ±55 ?11.25 to 98 dB OUTPUT CHARACTERISTICS RL = 2 kΩ ±10.6 pA/√Hz DC PERFORMANCE mV Input Offset Current Input Resistance (Differential) Ratio VCM = ±3 V Ω 1.2 20 11.75 dB INPUT kΩ Input Capacitance V Common-Mode Rejection Output Voltage Swing RL = 500 V Linear Output Current G = mA Short-Circuit Output Current 72 ±120 100 1, RL = 150 Ω, dc mA Capacitive Load Drive RS = 0 Ω, 12 FPBW = Slew Rate/(2π VPEAK). Multitone testing performed with 800 mV rms across a 500 Ω load at Point A and Point B on the circuit of Figure 23. 文档下载 免费文档下载 http://doc.guandang.net/ Rev. B | Page 3 of 16 AD8022 At 2http://doc.guandang.net/bbeb08690470a5ac86e08df20.html5°C, VS = ±2.5 V, RL = 500 Ω, G = 1, TMIN = –40°C, TMAX = Unit DYNAMIC PERFORMANCE 85°C, unless otherwise noted. Table 2. ?3 dB Small Signal Bandwidth VOUT = 50 mV p-p 100 120 MHz Bandwidth for 0.1 dB Flatness VOUT = 50 mV p-p Bandwidth1VOUT = 3 V p-p 4 voltage, G = 225 2 40 2 dBc Third Harmonic fC = 1 MHz ?94 differential, VS = ±6 V pA/√Hz DC PERFORMANCE Second Harmonic fC = 1 MHz ?69 dBc 144 kHz to 1.1 MHz INPUT CHARACTERISTICS Capacitance 0.7 Input Offset Voltage 2.0 5.0 μA TMIN to TMAX ?0.8 ±5.0 mV pF Input Common-Mode Voltage Range Common-Mode Rejection Ratio VCM = ±2.5 V, VS = ±5.0 V RL = 100 Ω, dc error = 1% ?1.38 to ±32 ?66.7 1.48 TMIN to TMAX Offset μA Open-Loop Gain Input Resistance (Differential) Output Voltage Swing RL = 500 Ω 7 2.3 nV/√Hz Input Current Noise f = 100 kHz Inpuhttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlt nA Input Bias Current ?77.5 dBc Multitone Input Power Ratio2G = 26 kHz to 132 kHz dBc Voltage Noise (RTI) f = 100 kHz ±65 75 ns VOUT = 150% of max output OUT = 2 V p-p mV V/μs Rise ns Settling Time 0.1% VOUT = 2 V p-p NOISE/DISTORTION PERFORMANCE 1 MHz Large Signal MHz Slew Rate VOUT = 2 V p-p, G = 2 30 42 and Fall Time VOUT = 2 V p-p, G = ns Overdrive Recovery Time 22 98 20 ?1.83 to Current 64 dB kΩ Input 2.0 V dB OUTPUT CHARACTERISTICS V Linear Output Current G = mA Short-Circuit Output Current 80 1, mA 文档下载 免费文档下载 http://doc.guandang.net/ Capacitive Load Drive RS = 0 Ω, 12 FPBW = Slew Rate/(2 π VPEAK). Multitone testing performed with 800 mV rms across a 500 Ω load at Point A and Point B on the circuit of Figure 23. Rev. B | Page 4 of 16 AD8022 ABSOLUTE MAXIMUM RATINGS Table 3. Supply Voltage ( VS to ?VSV Internal Power Dissipation1 8-Lead SOIC (R) 1.6 W 8-Lead MSOP (RM) 1.2 W Voltagehttp://doc.guandang.net/bbeb08690470a5ac86e08df20.html Input (Common Mode) ±VSDifferential Input Voltage ±0.8 V Output Short-Circuit Duration Observe Power Derating Curves Storage Temperature Range ?65°C to 125°C Operating Temperature Range 300°C Lead Temperature Range ?40°C to 85°C (A Grade) 文档下载 免费文档下载 http://doc.guandang.net/ (Soldering 10 sec) 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. MAXIMUM POWER DISSIPATION The maximum power that can be safely dissipated by the AD8022 is limited by the associated rise in junction temperature. The maximum safe junction temperature for plastic encapsulated devices is http://doc.guandang.net/bbeb08690470a5ac86e08df20.htmldetermined 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. While the AD8022 is internally short-circuit protected, this may not be sufficient to guarantee that the maximum junction temperature (150°C) is not exceeded under all conditions. To ensure proper operation, it is necessary to observe the maximum power derating curves. 2.0 文档下载 免费文档下载 http://doc.guandang.net/ MAXIMUM POWER DISSIPATION (W) 1 Specification is for the device in free air: 8-Lead SOIC: θJA = 160°C/W. 8-Lead MSOP: θJA = 200°C/W. 1.5 1.0 0.5 01053-003 AMBIENT TEMPERATURE (°C) Figure 3. Maximum Power Dissipation vs.http://doc.guandang.net/bbeb08690470a5ac86e08df20.html Temperature ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 文档下载 免费文档下载 http://doc.guandang.net/ 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 5 of 16 AD8022 TYPICAL PERFORMANCE CHARACTERISTICS 54321 (dB) (dB) 5 4 3210–1 0–1 文档下载 免费文档下载 http://doc.guandang.net/ –2–3–4–5FREQUENCY (MHz) 01053-004 FREQUENCY (MHz) 01053-007 –2–3–4–5 Figure 4. Frequency Response vs. RF, G = 1, VS = ±12 V, VIN = 63 mV p-p 0.40.30.20.10 (dB) ://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlarFigure 7. Frequency Response vs. Signal Level, VS = ±12 V, G = 1 54 FREQUENCY RESPONCE (dB) 3210–1 –2 –0.1–0.2–0.3–0.4–0.5–0.6–3–4–5FREQUENCY (kHz) 01053-008 文档下载 免费文档下载 http://doc.guandang.net/ FREQUENCY (Hz) 01053-005 140 Figure 5. Fine-Scale Gain Flatness vs. Frequency, G = 2 0.40.30.2 Figure 8. Frequency Response vs. Capacitive Load; CL = 0 pF and 50 pF; RS = 0 Ω 120100FREQUENCY (MHz) 0.10 (dB) 806040200 –0.1–0.2–0.3–0.4–0.5–0.6FREQUENCY (Hz) 01053-006 文档下载 免费文档下载 http://doc.guandang.net/ SUPPLY VOLTAGE (±V) 01053-009 Figure 6. Fine-Scale Gain Flatness vs. Frequency, G = 1 Figure 9. Bandwidth vs. Supply, RL = 500 Ω, VIN = 200 mV p-p Rev. B | Page 6 of 16 80706050 GAIN (dB) AD8022 INPUT 4030201http://doc.guandang.net/bbeb08690470a5ac86e08df20.html0 0–10 5k10k 100k 文档下载 免费文档下载 http://doc.guandang.net/ 1M10MFREQUENCY (Hz) 100M 01053-010 OUTPUT 01053-013 500M Figure 13. Noninverting Small Signal Pulse Response, RL = 500 Ω, VS = ±2.5 V, G = 1, RF = 0 Ω Figure 10. Open-Loop Gain vs. Frequency 180 INPUT FREQUENCY (Degrees) OUTPUT 文档下载 免费文档下载 http://doc.guandang.net/ 01053-014 –180 5k10k 100k 1M10MFREQUENCY (Hz) 100M 01053-011 500M Figure 14. Noninverting Large Signal Pulse Response, RL = 500 Ω, VS = ±12 V, G = 1, RF = 0 Ω INPUT Figure 11. Open-Loop Phase vs. Frequency INPUT OUTPUT 文档下载 免费文档下载 http://doc.guandang.net/ 01053-012 OUTPUT 01053-015 Figure 15. Noninverting Large Signal Pulse Response, RL = 500 Ω, VS = ±2.5 V, G = http://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlΩ Figure 12. Noninverting Small Signal Pulse Response, RL = 500 Ω, VS = ±12 V, G = Rev. B | Page 7 of 16 AD8022 0.40.30.2SETTLING ERROR (%) HARMONIC 1, RF = 0 Ω 1, RF = 0 文档下载 免费文档下载 http://doc.guandang.net/ DISTORTION (dB) –50–60–70–80–90–100–110–120–130 0.10–0.1–0.2 –0.4 –0.3 FREQUENCY (Hz) Figure 16. Settling Time to 0.1%, VS = ±12 V, Step Size = 2 V p-p, G = L = 500 Ω 0.40.30.2SETTLING ERROR (%) HARMONIC DISTORTION (dB) Figure 19. Distortion vs. Frequency, VS = ±12 V, RL = 500 Ω, RF = 0 Ω, VOUT = 2 V p-p, G = 1 2, R 文档下载 免费文档下载 http://doc.guandang.net/ –50–60–70–80–90–100–110 0.10–0.1–0.2 –0.3–0.4 –120–130 TIME (ns) FREQUENCY (Hz) Figure 17. Settling Time to 0.1%, VS = ±2.5 V, Step Size = 2 V p-p, G = 2http://doc.guandang.net/bbeb08690470a5ac86e08df20.html, RL = 500 Ω 7060 HARM ONIC DISTORTION (dBc) Figure 20. Distortion vs. Frequency, VS = ±2.5 V, 2 V p-p, G = –20–30 1 RL = 500 Ω, RF = 0 Ω, VOUT = 文档下载 免费文档下载 http://doc.guandang.net/ 50 SLEW RATE (V/μs) –40–50–60–70–80–90–100–120 40302010001053-018 SUPPLY VOLTAGE (V) OUTPUT VOLTAGE (V p-p) 01053-021 Figure 18. Slew Rate vs. Supply Voltage, G = 2 Figure 21. Distortion vs. Output Voltage, VS = ±12 V, G = 2, f = 1 MHz, RL = 500 Ω, RF = 715 Ω Rev. B | Page 8 of 16 –20) 文档下载 免费文档下载 http://doc.guandang.net/ cBd( NO–40 ) cITBRd(O VT–60 ISD/IDB Cd0IN1O–80 MRAH–100 –120 OUTPUT VOLTAGE (V p-p) Figure 22. Distortion vs. Output Voltage, VS = ±2.5 V, G = 1, f = 1 MHz, RL = 500 Ω, RF = 0 Ω ) cBd( VID/250Ω http://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlBd01 Figure 23. Multitone Power Ratio Test Circuit 文档下载 免费文档下载 http://doc.guandang.net/ ) c) cBdB(d ( VVIID/D/BdB0d101FREQUENCY (kHz) Figure 24. Multitone Power Ratio: VS = ±12 V, RL = 500 Ω, Full Rate ADSL (DMT), Downstream Rev. B | Page 9 of 16 AD8022 5 20-35010FREQUENCY (kHz) Figure 25. Multitone Power Ratio: VS = ±12 V, RL = 500 Ω, Full Rate ADSL (DMT), Upstream 6 20-35010FREQUENCY (kHz) Figure 26. Multitone Power Ratio: VS = ±6 V, RL = 500 Ω, Full Rate ADSL (DMT), Downstream 720-35010FREQUENCY (kHz) 文档下载 免费文档下载 http://doc.guandang.net/ Figure 27. Multitone Power Ratio: VS = ±6 V, RL = 500 Ω, Full Rate ADSL (DMT), Upstream AD8022 –0.5VOLTAGE OFFSET (mV) –50 –60 –1.5 –2.0 CMRR (dB) –1.0–70 –80 –90 01053-03 1 文档下载 免费文档下载 http://doc.guandang.net/ –2.5 TEMPhttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlERATURE (°C) –100 8.58.0TOTAL SUPPLY CURRENT (mA) FREQUENCYHz) Figure 28. Voltage Offset vs. Temperature 4.54.03.5BIAS CURRENT (μA ) Figure 31. CMRR vs. Frequency 7.57.06.5 6.05.55.03.02.5 2.01.51.0 0TEMPERATURE (°C) 文档下载 免费文档下载 http://doc.guandang.net/ TEMPERATURE(°C) 01 053-032 0.5 Figure 29. Bias Current vs. Temperature 4 321 VOS (mV) Figure 32. Total Supply Current vs. Temperature POWER SUPPLY REJECTION (dB) –10–20–30 –40–50 –60–70–80–90–100 文档下载 免费文档下载 http://doc.guandang.net/ FREQUENCY(Hz) 0–1–2 –3 –4 VCM(V) Figure 30. Voltage Offset vs. Input Common-Mode Voltage Figure 33. Power Supply Rejection vs. Frequency VS = ±12 V Rev. B | Page 10 of 16 0–10://doc.guandang.net/bbeb08690470a5ac86e08df20.html POWER SUPPLY REJECTION (dB) AD8022 0–10–20 CROSSTALK (dB) –20–30–40–50–60–70–80 文档下载 免费文档下载 http://doc.guandang.net/ –30–40–50–60–70–80–90–100 FREQUENCY(Hz) 01053-036 –90–100 FREQUENCY(Hz) Figure 34. Power Supply Rejection vs. Frequency VS = ±2.5 V 0–10–20 OUTPUT IMPEDANCE (Ω) Figure 36. Output-to-Output Crosstalk vs. Frequency, VS = ±2.5 V 10031103.1610.3160.10.0316 01053-035 01053-037 –30CROSSTALK (dB) –40 文档下载 免费文档下载 http://doc.guandang.net/ –50–60–70–80–90–100 FREQUENCY(Hz) 30k100k 1M10MFREQUENCY(Hz) 100M500M Figure 37. Output Impedance vs. Frequency, VS = ±12 V Figure 35. Output-to-Output Crosstalk vs. Frequency, VS = ±12 V Rev. B | Page 11 of 16 AD8022 THEORY OF OPERATION The AD8022 is voltaghttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmle-feedback a op amp designed especially for ADSL or other applications requiring very low voltage and current noise along with low supply current, low distortion, and ease of use. 文档下载 免费文档下载 http://doc.guandang.net/ The AD8022 is fabricated on Analog Devices’ proprietary eXtra-Fast Complementary Bipolar (XFCB) process, which enables the construction of PNP and NPN transistors with similar fTs in the 4 GHz region. The process is dielectrically isolated to eliminate the parasitic and latch-up problems caused by junction isolation. These features enable the construction of high frequency, low distortion amplifiers with low supply currents. S As shown in Figure 38, the AD8022 input stage consists of an NPN differential pair in which each transistor operates a 300 μA collector current. This gives the input devices a high transconductance and therefore gives the AD8022 a low input noise of 2.5 nV/√Hz @ 100 kHz. The input stage foldhttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmled drives cascode a that consists of a pair of PNP transistors. These PNPs then drive a current mirror that provides a differential input to single-ended output conversion. The output stage provides a high current gain of 10,000 so that the AD8022 can maintain a high dc open-loop gain, even into low load impedances. 01053-038 OUTPUT S 文档下载 免费文档下载 http://doc.guandang.net/ Figure 38. Simplified Schematic Rev. B | Page 12 of 16 AD8022 empty frequency bin. MTPR, sometimes referred to as the empty bin test, is typically expressed in dBc, similar to expressing the relative difference between single tone fundamentals and second or third harmonic distortion components. Measurements of MTPR are typically made at the output of the receiver directly across the differential load. Other components aside, the receiver function of an ADSL transceiver hybrid is affected ohttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlf by the turns the ratio selected transformers within the hybrid design. Since a transformer reflects the secondary voltage back to the primary side by the inverse of the turns ratio, 1/N, increasing the turns ratio on the secondary side reduces the voltage across the primary side inputs of the differential receiver. Increasing the turns ratio of the transformers can inadvertently cause a reduction of the SNR by reducing the received signal strength. APPLICATIONS The low noise AD8022 dual xDSL receiver amplifier is 文档下载 免费文档下载 http://doc.guandang.net/ specifically designed for the dual differential receiver amplifier function within xDSL transceiver hybrids, as well as other low noise amplifier applications. The AD8022 can be used in receiving modulated signals including discrete multitone (DMT) on either end of the subscriber loop. Communication systems designers can be challenged when designing an xDSL modem transceiver hybrid rechttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmleiving capable the of smallest signals embedded in noise that inherently exists on twisted-pair phone lines. Noise sources include near-end crosstalk (NEXT), far-end crosstalk (FEXT), background, and impulse noise, all of which are fed, to some degree, into the receiver front end. Based on a Bellcore noise survey, the background noise level for typical twisted-pair telephone loops is ?140 dBm/√Hz or 31 nV/√Hz. It is therefore important to minimize the noise added by the receiver amplifiers to preserve as much signal-to-noise ratio (SNR) as possible. With careful transceiver hybrid design, using the AD8022 dual, low noise, receiver amplifier to maintain power density levels lower than ?140 dBm/√Hz in ADSL modems is easily achieved. CHANNEL CAPACITY AND SNR The efficiency of an ADSL system in delivering the digital data embedded in the DMT signals can be compromised when the noise power of the transmission system increases. Fighttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlure 39 shows the relationship between SNR and the relative maximum number of bits per tone or subband while maintaining a bit error rate at 10–7 errors per second. 60 DMT MODULATION AND MULTITONE POWER RATIO (MTPR) ADSL systems rely on discrete multitone DMT modulation to carry digital data over 文档下载 免费文档下载 http://doc.guandang.net/ phone lines. DMT modulation appears in the frequency domain as power contained in several individual frequency subbands, sometimes referred to as tones or bins, each of which is uniformly separated in frequency. (See Figure 24 to Figure 27 for MTPR results while the AD8022 receives DMT driving 800 mV rms across a 500 Ω differential load.) A uniquely encoded quadrature amplitude modulation (QAM) signal occurs at the center frequency of each subband or tone. Difficulties exist when decoding these subbands if a QAM signal from one subband is corrupted by the QAM signal(s) from other subbands, regardless of whether thehttp://doc.guandang.net/bbeb08690470a5ac86e08df20.html corruption comes from an adjacent subband or harmonics of other subbands. Conventional methods of expressing the output signal integrity of line receivers, such as spurious-free dynamic range (SFDR), single tone harmonic distortion (THD), two-tone intermodulation distortion (IMD), and third-order intercept (IP3), become significantly less meaningful when amplifiers are required to process DMT and other heavily modulated waveforms. A typical xDSL downstream DMT signal can contain as many as 256 carriers (subbands or tones) of QAM signals. MTPR is the relative difference between the measured power in a typical subband (at one tone or carrier) vs. the power at another subband specifically selected to contain no QAM data. In other words, a selected subband (or tone) remains open or void of intentional power (without a QAM signal) yielding an 50 40 SNR (dB) 文档下载 免费文档下载 http://doc.guandang.net/ 30 20://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlr 10 01053-039 05 BITS/TONE 1015 Figure 39. ADSL DMT SNR vs. Bits/Tone POWER SUPPLY AND DECOUPLING The AD8022 should be powered with a good quality (that is, low noise) dual supply of ±12 V for the best overall performance. The AD8022 circuit also functions at voltages lower than ±12 V. Careful attention must be paid to decoupling the power supply pins. A pair of 10 μF capacitors located in near proximity to the AD8022 is required to provide good decoupling for lower frequency signals. In addition, 0.1 μF decoupling capacitors should be located as close to each of the power supply pins as is physically possible. 文档下载 免费文档下载 http://doc.guandang.net/ Rev. B | Page 13 of 16 AD8022 P13 Figure 40. DMT Signal Generator Schematic Rev. B | Page 14 of 16 6800pFCOMMON-MODEVOLTAGE –VIN –VOUhttp://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlT AD8022 LAYOUT CONSIDERATIONS VOUT VIN 01053-041 文档下载 免费文档下载 http://doc.guandang.net/ 6800pF5% NPO Figure 41. Differential Input Sallen-Key Filter Using AD8022 on Single Supply, 12 V 7.52.5–2.5–7.5–12.5(dB) As is the case with all high speed amplifiers, careful attention to printed circuit board layout details prevent associated board parasitics from becoming problematic. Proper RF design technique is mandatory. The PCB should have a ground plane covering all unused portions of the component side of the board to provide a low impedance return path. Removing the ground plane from the area near the input signal lines reduces stray capacitance. Chip capacitors should be used for supply bypassing. One end of the capacitor should be connected to the ground plane, and the other should be connected no more than 1/8 inch away from each supply pin. An additional large ://doc.guandang.net/bbeb08690470a5ac86e08df20.htmlar(0.47 μF to 10 μF) tantalum capacitor should be connected in parallel, although not necessarily as close, in order to supply current for fast, large signal changes at the AD8022 output. Signal lines connecting the feedback and gain resistors should be as short as possible, minimizing the inductance and stray capacitance associated with these traces. Locate termination resistors and loads as close as possible to the input(s) and output, respectively. Adhere to stripline design techniques for long signal traces (greater than about 1 inch). Following these generic guidelines improves the performance of the AD8022 in all applications. 文档下载 免费文档下载 http://doc.guandang.net/ –17.5–22.5–27.5–32.5–37.5–42.5 10k 100k1M FREQUENCY(Hz) 01053-042 10M Figure 42. Frequency Response of Sallen-Key Filter Rev. B | Page 15 of 16 AD8022 I OUTLINE DIMENSIONShttp://doc.guandang.net/bbeb08690470a5ac86e08df20.html COMPLIANT TO JEDEC STANDARDS MS-012-AA 文档下载 免费文档下载 http://doc.guandang.net/ CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FORREFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN Figure 43. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8)—Dimensions shown in millimeters and (inches) 0.10 PLANE COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 44. 8-Lead Mini Small Outline Package [MSOP] (RM-8)—Dimensions shown in millimeters ORDERING GUIDE Model AD8022AR AD8022AR-REEL AD8022AR-REEL7 AD8022ARZ1 文档下载 免费文档下载 http://doc.guandang.net/ AD8022ARZ-REEL1AD8022ARZ-REEL71AD8022ARM AD8022ARM-REEL AD8022ARM-REEL7 AD8022ARMZ1 AD8022ARMZ-REEL1AD8022ARMZ-REEL71 Temperature Range ?40°C to 85°C ?40°C 85°C ?40°C to to 85°C ?40°C to 85°C 85°C ?40°C to ?40°C to 85°Chttp://doc.guandang.net/bbeb08690470a5ac86e08df20.html ?40°C 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 to 85°C Package Description 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP Package Option R-8 R-8 R-8 R-8 R-8 R-8 RM-8 RM-8 RM-8 RM-8 RM-8 RM-8 1 Z = Pb-free part. ?2005 Analog Devices, nc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C01053?0–5/05(B) Rev. B | Page 16 of 16 文档下载 免费文档下载 http://doc.guandang.net/ 文档下载网是专业的免费文档搜索与下载网站,提供行业资料,考试资料,教 学课件,学术论文,技术资料,研究报告,工作范文,资格考试,word 文档, 专业文献,应用文书,行业论文等文档搜索与文档下载,是您文档写作和查找 参考资料的必备网站。 文档下载 http://doc.guandang.com/ 亿万文档资料,等你来下载