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Rail-to-Rail Upstream ADSL Line Driver AD45048
FEATURES
Dual op amp Voltage feedback Wide supply range: from 3.3 V to 24 V Rail-to-rail output Output swing to within 0.5 V of supply rails @ 230 mA 23 V p-p differential, RLOAD of 50 from 12 V supply High output current Linear output current of 230 mA peak into 25 -68 dBc MTPR @ 15 dBm (100 telephone line) Low noise 4.5 nV/Hz voltage noise density @ 100 kHz 1.5 pA/Hz current noise density @ 100 kHz High speed 65 MHz bandwidth (AV = 1, -3 dB) 55 V/s slew rate (RLOAD = 25 )
PIN CONFIGURATION
OUT1 1 -IN1 2 +IN1 3 -VS 4
8 7 6 5
+VS -IN2 +IN2
04817-Sp0-001
OUT2
Figure 1. 8-Lead SOIC
10 0 -10 -20 -30
dBm
-68dB -40 -50 -60
04817-Sp0-002
-70
APPLICATIONS
Consumer xDSL modems Twisted pair line drivers ADSL CPE applications (Drop in replacement for TS613ID and EL1519CS) Audio applications
-80 -90 CENTER 86.31174378kHz 1kHz/ SPAN 10kHz
Figure 2. AD45048AR Upstream ADSL MTPR (13 dBm, CF = 5.3)
GENERAL DESCRIPTION
The AD45048 ADSL CPE line driver is a dual operational amplifier capable of driving high output current (230 mA); it features a rail-to-rail output stage that swings to within 0.5 V of the supply rails. The AD45048 rail-to-rail output stage surpasses the output voltage capability of typical emitterfollower output stages and can deliver up to 23 V p-p differentially from a single 12 V supply in ADSL CPE line driving applications. The low distortion, high output current and wide output dynamic range make the AD45048 ideal for driving upstream signals in ADSL CPE applications. Fabricated with ADI's high speed XFCB-HV (eXtra Fast Complementary Bipolar-High Voltage) process, the high bandwidth and fast slew rate of the AD45048 keep distortion to a minimum while dissipating minimum power. The AD45048 is available in a standard 8-lead SOIC package that can operate from -40C to +85C.
Rev. A
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.
AD45048 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Pin Configuration............................................................................. 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 4 ESD Caution.................................................................................. 4 Typical Performance Characteristics ............................................. 5 General Description..........................................................................7 Power Supply and Decoupling.....................................................7 Layout Considerations..................................................................7 CPE ADSL Application ................................................................7 Transformer Selection ..................................................................7 Receive Channel Considerations.................................................7 Outline Dimensions ..........................................................................8 Ordering Guide .............................................................................8
REVISION HISTORY
9/05--Rev. 0 to Rev. A Updated Outline Dimensions ......................................................... 8 Changes to Ordering Guide ............................................................ 8 7/04--Revision 0: Initial Version
Rev. A | Page 2 of 8
AD45048 SPECIFICATIONS
VS = 6 V or +12 V (@ TA = 25C, G = +10, RL = 100 , unless otherwise noted). Table 1.
Parameter DYNAMIC PERFORMANCE -3 dB Bandwidth 0.1 dB Flatness Large Signal Bandwidth Large Signal Slew Rate NOISE/DISTORTION PERFORMANCE Distortion (Worst Harmonic) Multitone Power Ratio Input Voltage Noise Input Current Noise DC PERFORMANCE Input Offset Voltage Input Offset Voltage Match Input Bias Current TMIN - TMAX Input Offset Current Open-Loop Gain INPUT CHARACTERISTICS Input Resistance Input Capacitance OUTPUT CHARACTERISTICS Output Resistance Output Voltage Swing Differential Output Voltage Swing Single-Ended +Swing Single-Ended -Swing Single-Ended +Swing Single-Ended -Swing Operating Range (Dual Supply) Supply Current Power Supply Rejection Ratio Common-Mode Rejection Ratio 85 f = 100 kHz Test Conditions/Comments G = +1, VOUT = 0.1 V p-p, RFB = 0 , RLOAD = 25 VOUT = 0.1 V p-p single-ended, G = +1, RLOAD = 25 VOUT = 1 V p-p single-ended, G = +10, RLOAD = 25 VOUT = 5 V p-p, G = +1, RLOAD = 25 fC = 40 kHz, VOUT = 6 V p-p, single-ended, RLOAD = 25 26 kHz to 134 kHz, ZLINE = 100 , XFMR = 1:2 turns, PLINE = 13 dBm f = 100 kHz f = 100 kHz Min Typ 65 3.35 4.5 55 -80 -68 4.5 1.5 1 2.5 1 200 1.3 50 94 87 1.4 2.5 2.0 900 300 Max Unit MHz MHz MHz V/s dBc dBc nV/Hz pA/Hz mV mV mV nA A nA dB k pF
TMIN - TMAX
1.4 MHz; G = +1 Maximum swing (differential) VOMAX, RLOAD = 50 differential Minimum swing (differential) VOMIN, RLOAD = 50 differential VOUT = VOMAX - VOMIN RLOAD = 25 RLOAD = 25 RLOAD = 100 RLOAD = 100
11.25 22.5 5.68 5.92 1.5 7
0.2 11.5 -11.5 23 5.76 -5.67 5.95 -5.91 9 -85 -86
-11.25
-5.58 -5.86 12.6 12 -75 -79
0.5 V 1 V
V diff V diff V p-p Vp Vp Vp Vp V mA dB dB
Rev. A | Page 3 of 8
AD45048 ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Supply Voltage Power Dissipation Storage Temperature Operating Temperature Range Lead Temperature Range (Soldering 10 sec) Junction Temperature Rating 26.4 V (TJMAX - TA)/JA 1 -65C to +125C -40C to +85C 300C 150C
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.
1
JA = 112.7C/W for SOIC package in still air based on 2S2P JEDEC PCB.
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. A | Page 4 of 8
AD45048 TYPICAL PERFORMANCE CHARACTERISTICS
25 G = +10 20 15 10 GAIN (dB) 5 G = +1 0 -5 -10
04817-Sp0-017
499 RG
- +
25 20 15 G = +10 G = +5 RG
499
- +
G = +5
25 G = +2 GAIN (dB)
10 G = +2 5 G = +1 0 -5 -10
25
-20 -25 10k 100k 1M 10M FREQUENCY (Hz) 100M 1G
-20 -25 10k 100k 1M 10M FREQUENCY (Hz) 100M 1G
Figure 3. Noninverting Small Signal Bandwidth (VS = 6 V, VO = 0.1 V p-p, RL = 25 )
Figure 6. Noninverting Large Signal Bandwidth (VS = 6 V, VO = 1 V p-p, RL = 25 )
25 20 15 10 G = -2 GAIN (dB) G = -10 G = -5 RG
- +
5k
25 G = -10 20 15 G = -5 RG
- +
5k
25 10 GAIN (dB) 5 G = -1 0 -5 -10
04817-Sp0-025
25 G = -2
5 G = -1 0 -5 -10 -15 -20 -25 10k 100k 1M 10M FREQUENCY (Hz) 100M 1G
-20 -25 10k 100k 1M 10M FREQUENCY (Hz) 100M 1G
Figure 4. Inverting Small Signal Bandwidth (VS = 6 V, VO = 0.1 V p-p, RL = 25 )
Figure 7. Inverting Large Signal Bandwidth (VS = 6 V, VO = 1 V p-p, RL = 25 )
-40
R2 3k +12V
-50
+VIN
MTPR -60
R1 499
2
8
0.1F
4.7F TANT 1 R3 12.5 TX1 R3 100
V+ OUT 3 U1A
AD45048
+6V
-70
04817-Sp0-027
5 R4 499 OUT 6 V- 7
R6 12.5
1:2
-80 0 5 10 dBm (100) 15 20
Figure 5. MTPR vs. Line Power (See Schematic in Figure 8)
Figure 8. Differential Test Circuit for MTPR
Rev. A | Page 5 of 8
04817-Sp0-014
-VIN
U1B 4 AD45048 R5 3k
04817-Sp0-018
-15
04817-Sp0-026
-15
-15
AD45048
100 100
CURRENT NOISE (pA/ Hz)
04817-Sp0-019
VOLTAGE NOISE (nV/ Hz)
10
10
1 10
100
1k
10k 100k FREQUENCY (Hz)
1M
10M
100M
1 10
100
1k
10k 100k FREQUENCY (Hz)
1M
10M
Figure 9. Voltage Noise vs. Frequency, VS = 6 V
Figure 12. Input Current Noise vs. Frequency, VS = 6 V
0
1000
-20 OUTPUT IMDEDANCE ()
100
DISTORTION (dBc)
-40
10
-60 SECOND -80
1
0.1
04817-Sp0-028
-100 THIRD -120 1 2 3 4 5 6 7 8 OUTPUT VOLTAGE (p-p) 9 10 11
0.01
0.001 10k
100k
1M 10M FREQUENCY (Hz)
100M
Figure 10. Single-Ended Harmonic Distortion, VS = 6 V dc, G = +6, RF = 499 , RG = 100 , RL = 25 , Fundamental Frequency = 40 kHz
Figure 13. Output Impedance vs. Frequency
04817-Sp0-029
2V/DIV M 5.00s
50mV/DIV M 100ns
Figure 11. Discrete Multitone Modulation Overdrive Recovery (See Schematic in Figure 8)
Figure 14. Small Signal Pulse Response RLOAD = 1 k, RFB = 500
Rev. A | Page 6 of 8
04817-Sp0-031
04817-Sp0-030
04817-Sp0-020
AD45048 GENERAL DESCRIPTION
The AD45048 is a voltage feedback, rail-to-rail output amplifier with high output current capability. Fabricated on Analog Devices' proprietary high speed eXtra fast complementary bipolar high voltage process (XFCB-HV), the high bandwidth and fast slew rate of the AD45048 keep distortion to a minimum while dissipating minimum power. The XFCB-HV, silicon-on-insulator (SOI) process prevents latch-up problems and enables the construction of high frequency, low distortion amplifiers, such as the AD45048.
CPE ADSL APPLICATION
The low cost, high output current dual AD45048 xDSL line driver amplifiers have been specifically designed to drive high fidelity xDSL signals to within 0.5 V of the power rails on a single 12 V supply. The AD45048 can be used in transformercoupled bridge hybrid circuits designed to drive modulated signals, including discrete multitone (DMT), upstream to the central office.
POWER SUPPLY AND DECOUPLING
The AD45048 can be powered with a good quality, well regulated, low noise supply anywhere in the range from +3 V to 12.6 V. In order to optimize the AD45048 in standard ADSL CPE line driver applications (see Figure 8), power the amplifier with a well regulated 12 V supply. Careful attention should be paid to decoupling the power supply. High quality capacitors with low equivalent series resistance (ESR), such as multilayer ceramic capacitors (MLCCs), should be used to minimize the supply voltage ripple and power dissipation. A 0.1 F MLCC decoupling capacitor(s) should be located no more than 1/8-inch away from the power supply pin(s). A large, usually tantalum, 10 F to 47 F capacitor is recommended to provide good decoupling for lower frequency signals and to supply current for fast, large signal changes at the AD45048 outputs.
TRANSFORMER SELECTION
Customer premise ADSL applications require the transmission of a 13 dBm DMT signal (20 mW into 100 ). DMT signals can have a crest factor (V peak/V rms ratio) as high as 5.3, requiring the line driver to provide a peak power of 560 mW. The line driver is required to drive a 7.5 V peak onto the 100 telephone line while maintaining about -65 dBc to -70 dBc of MTPR. Since the maximum low distortion output swing available from the AD45048 line driver is approximately 11.5 V on a 12 V supply (depending on the load), and taking into account the power lost in the transformer and termination resistors, a step-up transformer with a minimum turns ratio of 1.5 or greater is needed. In the simplified differential driver circuit shown in Figure 8, the AD45048 is driving a 25 impedance reflected by 1:2 step-up transformer. R3 and R6 are 12.5 each and are back-termination or load-matching resistors whose values can be calculated by (100 /(N2))/2 where 100 is the approximate phone line impedance and N is the transformer turns ratio. In Figure 8, the total differential load including the termination resistors is 50 , and under these conditions, the AD45048 is capable of driving low distortion signals to within 0.5 V of the power rails.
LAYOUT CONSIDERATIONS
As is the case with all high speed applications, careful attention to printed circuit board layout details prevents associated board parasitics from becoming problematic. Proper RF layout and printed circuit board design techniques are strongly recommended. The PCB should have a low impedance return path (or ground) to the supply. Removing the ground plane from all layers in the immediate area of the amplifier reduces stray capacitances. The signal routing should be short and direct in order to minimize the parasitic inductance and capacitance associated with these traces. Termination resistors and loads should be located as close as possible to their respective inputs and outputs. Input traces should be kept as far apart as possible from the output traces to minimize coupling (crosstalk) though the board. Wherever there are complementary signals, a symmetrical layout should be provided to the extent possible in order to maximize balanced performance. When running differential signals over a long distance, the traces on the PCB should be close together or any differential wiring should be twisted together to minimize the area of the loop that is formed. This reduces the radiated energy and makes the circuit less susceptible to RF interference. Adherence to stripline design techniques for long signal traces (greater than about 1 inch) is recommended.
RECEIVE CHANNEL CONSIDERATIONS
A step-up transformer of N turns used at the output of the differential line driver increases the differential output voltage to the line (see Figure 8). However, the inverse effect is seen in the receive channel as the amplitude of signal on the driver side of the transformer is divided by N turns. The decision to use a particular transformer turns ratio may be impacted by the ability of the receive circuitry to resolve low level signals in the noisy twisted pair telephone plant. Higher turns ratio transformers reduce the effective receive channel SNR (signalto-noise ratio) due to the reduction in the received signal strength. An amplifier with low RTI noise, such as the AD8022 (2.5 nV/Hz), is recommended for the receive channel. For a complete selection of amplifiers and other related components, see www.analog.com.
Rev. A | Page 7 of 8
AD45048 OUTLINE DIMENSIONS
5.00 (0.1968) 4.80 (0.1890)
8 5
4.00 (0.1574) 3.80 (0.1497) 1
6.20 (0.2440)
4 5.80 (0.2284)
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)
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)
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
Figure 15. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model AD45048AR AD45048AR-REEL AD45048AR-REEL7 AD45048ARZ 1 AD45048ARZ-REEL1 AD45048ARZ-REEL71
1
Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C
Package Description 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N) 8-Lead Standard Small Outline Package (SOIC_N)
Package Option R-8 R-8 R-8 R-8 R-8 R-8
Z = Pb-free part.
(c) 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04817-0-9/05(A)
Rev. A | Page 8 of 8

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