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PDF MAX9480 Data sheet ( Hoja de datos )
| Número de pieza | MAX9480 | |
| Descripción | Low-Power / Low-Distortion / Central-Office ADSL Drivers and Integrated Drivers/Receivers | |
| Fabricantes | Maxim Integrated | |
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19-2539; Rev 1; 1/03
Low-Power, Low-Distortion, Central-Office
ADSL Drivers and Integrated Drivers/Receivers
General Description
The MAX9480/MAX9481/MAX9482 low-power, low-dis-
tortion, class-G, high-current asymmetric digital sub-
scriber line (ADSL) drivers offer Rail-to-Rail® output and
are ideal for ADSL in central-office applications.
Operating from ±5V and ±2.5V supplies, the drivers
incorporate two high-speed current-feedback preampli-
fiers driving two fixed-gain class-G buffers. The buffers
can deliver 20.4dBm average line power with a signal
crest factor of 5.3, and are designed to be directly DC or
AC bridged across a 1:2.5 transformer.
The MAX9480/MAX9481/MAX9482 employ an active line
termination scheme for incoming signals that eliminates
the need for back-match resistors, reducing line-card
power consumption at full rate to less than half of that
required by conventional class-AB line-driver circuits.
The MAX9480 includes a hybrid network and two low-
noise, fixed-gain-of-4.6V/V receive amplifiers. The part is
designed to recover the receive signal to the same level
as that of a conventional line interface circuit that incor-
porates a 1:2 transformer and standard back-matched
hybrid, without degrading signal-to-noise ratio (SNR) or
line-impedance sensitivity. The MAX9481 provides only
the preamplifiers and buffers without the hybrid or
receivers. The MAX9482 provides preamplifiers, buffers,
and uncommitted receive amplifiers. All devices have a
low-output-impedance shutdown function for saving
power when not transmitting.
At full-rate 20.4dBm discrete multitone data transmission
(DMT), the total dynamic power dissipation is only
680mW (MAX9480/MAX9482) or 655mW (MAX9481).
The MAX9480/MAX9481 are available in a 20-pin TSSOP
package and the MAX9482 is available in 28-pin TSSOP
and 32-pin QFN packages. All devices operate over the
extended -40°C to +85°C temperature range.
Applications
Full-Rate ADSL
HDSL
Central Office
DSLAM
Typical Operating Circuits appear at end of data sheet.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
Features
o Dissipate Only 655mW While Driving 20.4dBm
ADSL Full-Rate DMT-Modulated Signal
o Operate with ±5.0V and ±2.5V Power Supplies
o Complete ADSL Central-Office Line Interface
(MAX9480/MAX9482)
Two Preamplifiers plus Class-G Rail-to-Rail
Buffers
Active Line Termination plus Integrated Hybrid
(MAX9480)
Low-Noise Uncommitted Receive Amplifiers
(MAX9482)
Fixed-Gain Receive Amplifiers (MAX9480)
Low-Output-Impedance Shutdown Mode
o Preamplifiers, Buffers, and Active Line
Termination Functions (MAX9481)
o High-Output-Drive Capability
15VP-P Differential Output Voltage Swing at
RL = 16Ω
500mA Output-Drive
o Low Distortion: -71dBc Highest Harmonic at 1MHz
and 14VP-P
o High Speed: 250V/µs Slew Rate, 80MHz -3dB
Bandwidth (G = -3)
o Thermal Shutdown
o Exposed Pads Improve Thermal Performance
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX9480CUP
-40°C to +85°C
20 TSSOP-EP**
MAX9481CUP
-40°C to +85°C
20 TSSOP-EP
MAX9482CUI
-40°C to +85°C
28 TSSOP-EP
MAX9482CGJ*
-40°C to +85°C
32 QFN
*Future product—contact factory for availability.
**EP = Exposed pad.
Pin Configurations
TOP VIEW
POUT1 1
IN1- 2
IN1+ 3
RXP 4
DGND 5
SHDN 6
RXM 7
IN2+ 8
IN2- 9
POUT2 10
MAX9480
20 VLM
19 VLP
18 VCC
17 OUT1
16 VEE
15 VEE
14 OUT2
13 VCC
12 VLP
11 VLM
TSSOP
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
Low-Power, Low-Distortion, Central-Office
ADSL Drivers and Integrated Drivers/Receivers
Typical Operating Characteristics
(VCC = +5V, VEE = -5V, VLP = +2.5V, VLM = -2.5V, DGND = 0, RXIN1+ = RXIN2+ = 0, IN1+ = IN2+ = 0, RL = 16Ω is connected from
OUT1 to OUT2, SHDN = 0, TA = +25°C, unless otherwise noted. Preamp configured for AV = +1 with 1kΩ from RXOUT_- to RXIN_-.
Receiver configured for AV = +1 with 1kΩ from POUT_ to IN_-.)
SUPPLY CURRENT vs. OUTPUT VOLTAGE
600
= ±5V SUPPLY
= ±2.5V SUPPLY
500
IDC
INPUT = DC
400
300
fINPUT = 1MHz
IAVG
IAVG
200
fINPUT = 100kHz
100
SUPPLY CURRENT vs. TEMPERATURE
30
MAX9481
26
22 2.5V SUPPLY
18 5V SUPPLY
14
SHUTDOWN CURRENT vs. TEMPERATURE
3.0
MAX9481
2.4
1.8 2.5V SUPPLY
1.2
5V SUPPLY
0.6
0
0 1 2 3 4 5 6 7 8 9 10
VOUTP-P (V)
10
-40
-15 10 35 60
TEMPERATURE (°C)
85
0
-40
-15 10 35 60
TEMPERATURE (°C)
85
TRANSMIT PATH
FREQUENCY RESPONSE
80 MAX9480 toc04 -140
OVERALL GAIN = -9V/V
60 PREAMP GAIN = +3V/V
-160
40 -180
DRIVER HARMONIC DISTORTION
vs. FREQUENCY
0
VOUTP-P = 2.0V
-20
20
0
OVERALL GAIN = -3V/V
-20 PREAMP GAIN = +1V/V
-200 -40
-220 2ND HARMONIC
-240 -60
-40
-60
-80
0.01
= GAIN
= PHASE
0.1 1 10
FREQUENCY (MHz)
-260
-280
-300
100
-80
-100
0.01
23NRD HARMONIC
0.1 1
FREQUENCY (MHz)
10
DRIVER HARMONIC DISTORTION
vs. OUTPUT VOLTAGE
0
f = 1MHz
-10
-20
-30
-40 23NRD HARMONIC
-50 2ND HARMONIC
-60
-70
-80 SUPPLY CROSSOVER REGION
-90
-100
2 4 6 8 10 12 14 16 18
VOUT (DIFF) (VP-P)
RECEIVER AMPLIFIER
FREQUENCY RESPONSE
MAX9480 toc07
30 135
A
20
B
90
10
C
0
-10
-20
B
AC
45
0
-45
-30 = GAIN
= PHASE
-90
-40 -135
0.01 0.1 1 10 100 1000
FREQUENCY (MHz)
A: GAIN = 10V/V
C: GAIN = 1V/V
B: GAIN = 5V/V
_______________________________________________________________________________________ 5
5 Page 
Low-Power, Low-Distortion, Central-Office
ADSL Drivers and Integrated Drivers/Receivers
ZOUT = 8Ω
1:2.5 LINE +
Tx PORT
LINE PORT ZIN = 16Ω
ZOUT = 100Ω
ZOUT = 8Ω
LINE -
Figure 5. Output Equivalent Circuit
With a 1:2.5 transformer, the two 8Ω impedances real-
ized by the active-feedback network form a perfect line
termination. The MAX9480 family’s active termination
design makes it possible to use a ±5V power supply
instead of ±12V or ±15V, significantly increasing driver
efficiency.
Hybrid Considerations
The MAX9480 includes an internal hybrid coupling cir-
cuit to realize the receive function with no external com-
ponents. The hybrid couples the transmitted signal
from the line-driver port (Tx port) to the line port and
cancels the echo in the receiving port (Rx port). The
hybrid circuit is detailed in Figure 6. If using the
MAX9481 or the MAX9482, external circuitry must be
added to realize a receive function. The MAX9482
includes two uncommitted op amps for this purpose.
A traditional hybrid network with a 2:1 resistor ratio
must be replaced with a 1.2:1 ratio to achieve nominal
echo cancellation. Additionally, the use of a synthe-
sized output impedance has the side effect of prevent-
ing a “virtual-ground” condition at the driver output
(BOUT), as seen by the receive signal. Hence, the
resulting hybrid circuit exhibits an increased attenua-
tion of the receive signal with respect to a traditional
case with no synthesis. For central-office ADSL appli-
cations, the noise specifications allow this trade-off to
be made.
Pseudo-Class-G Amplifier
The driver consists of two stages: the current-feedback
preamplifier and the voltage-feedback buffer. To save
power, the preamplifier uses a power supply of only
±2.5V. The output swing of the preamplifier is about
3.0VP-P. The buffer is designed as a pseudo-class-G
amplifier with a fixed gain of -3V/V. This buffer stage
employs two power supplies: a lower voltage supply,
±2.5V, and a higher voltage supply, ±5V. In the differ-
ential driver, two parallel amplifiers provide the output
current to the load, as shown in Figure 7.
In this pseudo-class-G amplifier, there is no abrupt
supply switchover between the higher voltage and the
lower voltage amplifiers, as in a traditional class G. It is
a seamless transition that depends only on the ampli-
tude of the input signal and the gain. The lower voltage
amplifier has a high conversion conductance, GA, and
the higher voltage amplifier has a low conductance, GB.
With a low input voltage, the lower voltage amplifier pro-
vides most of the output current to the load. As the volt-
age of the input signal increases, the lower voltage
amplifier starts to saturate and the higher voltage ampli-
fier begins to drive the output.
MAX9480
0.8Rx
Tx
R4
1.2kΩ
R1
1.6Ω
Tx
PORT
R6
1.2kΩ
R2
1.6Ω
-0.8Rx
-Tx
(a) HYBRID CIRCUIT IN MAX9480
Rx
0.8Tx
OUT1
R3
1kΩ
LINE
PORT
RXM
0Tx + 0.18Rx
0Tx - 0.18Rx
RXP
Rx
PORT
R5
1kΩ
OUT2
-Rx
-0.8Tx
0Rx
Tx
8Ω
2kΩ
Tx
PORT
2kΩ
8Ω
-0.0Rx
-Tx
(b) TRADITIONAL HYBRID CIRCUIT
Rx
0.5Tx
OUT1
1kΩ
LINE
PORT
RXM
0Tx + 0.67Rx
0Tx - 0.67Rx
RXP
Rx
PORT
1kΩ
OUT2
-Rx
-0.5Tx
Figure 6. Hybrid Circuit in the MAX9480
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet MAX9480.PDF ] | |
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