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PDF AD8390 Data sheet ( Hoja de datos )
| Número de pieza | AD8390 | |
| Descripción | High Output Current Differential Amplifier | |
| Fabricantes | Analog Devices | |
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FEATURES
Voltage feedback amplifier
Ideal for ADSL and ADSL2+ central office (CO) and
customer premises equipment (CPE) applications
Enables high current differential applications
Low power operation
Single- or dual-power supply operation from 10 V (±5 V)
up to 24 V (±12 V)
4 mA total quiescent supply current for full power ADSL
and ADSL2+ CO applications
Adjustable supply current to minimize power
consumption
High output voltage and current drive
400 mA peak output drive current
44.2 V p-p differential output voltage
Low distortion
–82 dBc @ 1 MHz second harmonic
–91 dBc @ 1 MHz third harmonic
High speed: 300 V/µs differential slew rate
APPLICATIONS
ADSL/ADSL2+ CO and CPE line drivers
xDSL line driver
High current differential amplifiers
GENERAL DESCRIPTION
The AD8390 is a high output current, low power consumption
differential amplifier. It is particularly well suited for the central
office (CO) driver interface in digital subscriber line systems
such as ADSL and ADSL2+. While in full bias operation, the
driver is capable of providing 24.4 dBm output power into low
resistance loads. This is enough to power a 20.4 dBm line while
compensating for losses due to hybrid insertion, transformer
insertion, and back termination resistors.
The AD8390 fully differential amplifier is available in a ther-
mally enhanced lead frame chip scale package (LFCSP-16) and
a 16-lead QSOP/EP. Significant control and flexibility in bias
current have been designed into the AD8390. The four power
modes are controlled by two digital bits, PWDN (1,0) which
provide three levels of driver bias and one powered-down state.
In addition, the IADJ pin can be used for fine quiescent current
trimming to tailor the performance of
the AD8390.
Low Power, High Output Current
Differential Amplifier
AD8390
PIN CONFIGURATIONS
NC VOCM NC
16
NC
13
+IN 1
PWDN1
PWDN0
–IN 4
12 –OUT
VEE
VCC
9 +OUT
5
NC DGND IADJ
NC = NO CONNECT
8
NC
Figure 1. 4 mm × 4 mm 16-Lead LFCSP
VOCM
1
16 NC
NC –OUT
+IN NC
PWDN1
PWDN0
–IN
VEE
VCC
NC
NC +OUT
DGND
8
9 IADJ
NC = NO CONNECT
Figure 2. 16-Lead QSOP/EP
The low power consumption, high output current, high output
voltage swing, and robust thermal packaging enable the AD8390
to be used as the central office line driver in ADSL, ADSL2+,
and proprietary xDSL systems, as well as in other high current
applications requiring a differential amplifier.
Rev. C
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: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.
1 page  
AD8390
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter
Supply Voltage
VOCM
Package Power Dissipation
Maximum Junction Temperature (TJ MAX)
Operating Temperature Range (TA)
Storage Temperature Range
Lead Temperature (Soldering 10 s)
Rating
±13.2 V (26.4 V)
VEE < VOCM < VCC
(TJ MAX – TA)/θJA
150°C
–40°C to +85°C
–65°C to +150°C
300°C
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.
TYPICAL THERMAL PROPERTIES
Table 4.
Package
16-lead LFCSP (CP-16)
JEDEC 2S2P – 0 airflow
Paddle soldered to board
Nine thermal vias in pad
16-lead QSOP/EP (RC-16)
JEDEC 1S2P – 0 airflow
Paddle soldered to board
Nine thermal vias in pad
Typical Thermal Resistance (θJA)
30.4°C/W
44.3°C/W
49.9Ω
RG = 1kΩ
RF = 10kΩ
VIN
RG = 1kΩ
AD8390
RL,DM = 100Ω VOUT,DM
49.9Ω
RF = 10kΩ
Figure 3. Basic Test Circuit
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. C | Page 5 of 16
5 Page 
AD8390
VCC
0.1µF
10µF
R2
R3
R1
+IN
0.1µF
VOCM
R1 0.1µF
–IN
VEE
0.1µF
10µF
RADJ
–OUT RM
+OUT
R3
RM
R2
1:N
+
RL VOUT,DM
–
Figure 24. ADSL/ADSL2+ Application Circuit
Referring to Figure 24, the following describes how to calculate
the resistor values necessary to obtain the desired input imped-
ance, gain, and output impedance.
The differential input impedance to the circuit is simply 2R1.
As such, R1 is chosen by the designer to yield the desired input
impedance.
When synthesizing the output impedance, a factor k is
introduced, which is used to express the ratio of the negative
feedback resistor to the positive feedback resistor by
1 − k = R3
R2
(5)
Along with the turns ratio N, k is also used to define the value of
the back termination resistors RM. Commonly used values for k
are 0.1 to 0.25. A k value of 0.1 would result in back termination
resistors that are only 1/10 as large as those in the simplest case
described above. Lower values of k result in greater amounts of
positive feedback. Therefore, values much lower than 0.1 can
lead to instability and are generally not recommended.
RM
=
k
×
2
RL
×N
2
(6)
This factor (k), along with R1, RM, and the desired gain (AV), is
then used to calculate the necessary values for R3 and R2.
( )R3 = AV × R1× k + AV × R1 × AV × R1× k 2 + R M − k × R M
(7)
The usually small value for RM allows a simplified approximation
for R3.
R3 ≅ R1 × 2 × k × AV
(8)
R2 = R3
1−k
(9)
Once RM, R3, and R2 are computed, the closest 1% resistors can
be chosen and the gain rechecked with the following equation:
( )AV
=
RM
R2×R3
+k ×R2+R2−R3
×R1
(10)
Table 6 shows a comparison of the results using the exact values,
the simplified approximation, and the closest 1% resistor values.
In this example, R1, AV, and k were chosen to be 1.0 kΩ, 10 kΩ,
and 0.1 kΩ, respectively.
It should be noted that decreasing the value of the back termi-
nation resistors attenuates the receive signal by approximately
1/k. However, advances in low noise receive amplifiers permit
k values as small as 0.1 to be commonly used.
The line impedance, turns ratio, and k factor specify the output
voltage and current requirements from the AD8390. To accom-
modate higher crest factors or lower supply rails, the turns ratio,
N, may have to be increased. Since higher turns ratios and smaller
k factors both attenuate the receive signal, a large increase in N
may require an increase in k to maintain the desired noise
performance. Any particular design process requires that these
trade-offs be visited.
Table 6. Resistor Selection
Component
R1 (Ω)
R2 (Ω)
R3 (Ω)
RM (Ω)
Actual AV
Actual k (Eq. 5)
Exact
Values
1000
2246.95
2022.25
5
10.000
0.1
Approximate
Calculation
1000
2222.22
2000
5
9.889
0.1
Standard 1%
Resistor
Values
1000
2210
2000
4.99
10.138
0.095
MULTITONE POWER RATIO (MTPR)
Multitone power ratio is a commonly used figure of merit that
xDSL designers use to help describe system performance.
MTPR is the measured delta between the peak of a filled
frequency bin and the harmonic products that appear in an
intentionally empty frequency bin. Figure 25 illustrates this
principle. The plots in Figure 10 and Figure 13 show MTPR
performance in various power modes. All data were taken with
a circuit with a k factor of 0.1, a 1:1 turns ratio transformer, and
a waveform with a 5.4 peak-to-average ratio, also known as the
crest factor (CF).
10dB/DIV
–70dBc
CENTER 431.25kHz
1kHz/DIV
SPAN 10kHz
Figure 25. MTPR Measurement
Rev. C | Page 11 of 16
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AD8390.PDF ] | |
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