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PDF ISL1550 Data sheet ( Hoja de datos )
| Número de pieza | ISL1550 | |
| Descripción | VDSL2 Differential Line Driver | |
| Fabricantes | Intersil | |
| Logotipo |  |
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Single Port, VDSL2 Differential Line Driver
ISL1550
The ISL1550 is a dual operational amplifier intended to be
used as a differential line driver. ISL1550’s high bandwidth
and low distortion performance enables the support of VDSL2
8b, 17a and 30a modem applications.
This device features a high current drive capability of ±750mA
required to drive large voltage peaks into heavy loads. In
Central Office (CO) applications, the driver achieves a typical
Missing Band Power Ratio (MBPR) of -66dBc in VDSL2 8b
upstream (US) 1 band and MBPR’s of -61dBc and -60dBc in
VDSL2 17a US1 and US2 respectively.
The ISL1550 has two bias current control pins (C0, C1) to allow
for four power settings (disable, low, medium, high). The VDSL
modem DSP configures the line driver’s power setting based
on the desired mode of operation. The line driver operates on a
nominal single +12V or a dual ±6V supplies with bias current
in active mode between 15mA to 32mA, depending on its
power setting. The ISL1550’s gain setting is configurable at
the application level by setting the Rf and Rg resistor values.
The surge current handling of ISL1550 has been enhanced to
allow ITU-T K.20 and GR1089 compliance with minimal
external surge protection circuitry.
The ISL1550 is available in the thermally-enhanced, Pb-free
RoHS compliant 16 Ld QFN package and is specified for
operation over the full -40°C to +85°C temperature range.
Features
• 20dBm output power capability
• Drives up to ±750mA from a +12V supply
• 18VP-P differential output drive into 20Ω
• -89dBc typical driver output distortion at full output at
200kHz, 12VP-P differential
• -61dBc US1, -60dBc US2 avg. MBPR 17a
• Supply range: ±4.0V to ±6.6V, +8.0V to +13.2V
• Thermal shutdown
• K.20, GR-1089 Surge Robustness Validated
Applications
• VDSL2 Profiles: 8MHz, 17MHz, and 30MHz
Related Literature
• AN1325 “Choosing and Using Bypass Capacitors”
PART #
ISL1557
ISL1539A
TABLE 1. ALTERNATE SOLUTIONS
NOMINAL ±VCC
(V)
BANDWIDTH
(MHz)
APPLICATIONS
±6,+12
200
VDSL2
±12,+24
240
VDSL2
100n
500
AFE
Rg
1.5k
2.2n
500
100n
+6V
SUPPLY
DECOUPLING
NOT SHOWN
+
½
ISL1550
-
Rf
750
1k
Rf
- 750
½
ISL1550
+
1k
2.2
1:2.5
100
NOMINAL
LINE
2.2
-6V
FIGURE 1. TYPICAL APPLICATION CIRCUIT
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
8.40M 8.90M 9.40M 9.90M 10.4M 10.9M 11.4M 11.9M
FREQUENCY (Hz)
FIGURE 2. US2 MBPR 17a VDSL2 PERFORMANCE
March 16, 2012
FN6795.0
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 |Copyright Intersil Americas Inc. 2012. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
1 page  
ISL1550
Typical Performance Curves
noted.
6
VCC = ±6V, See Figure 1, TA = +25°C, C0 = C1 = 0V (Full power), Unless otherwise
6
3
25Ω
0
50Ω
-3
3
0
-3 33pF
18pF
-6 16Ω
-9
-6
-9
22pF
-12
1M
10M
100M
1G
FREQUENCY (Hz)
FIGURE 4. SMALL SIGNAL FREQUENCY RESPONSE vs RLOAD
-12
1M
10M
100M
FREQUENCY (Hz)
1G
FIGURE 5. SMALL SIGNAL FREQUENCY RESPONSE vs CLOAD
6
3
0
-3
VCC = 12V TO 8V
-6
-9
-12
1M
10M
100M
FREQUENCY (Hz)
1G
FIGURE 6. SMALL SIGNAL BANDWIDTH vs SUPPLY VOLTAGE
6
3
0 1VP-P
-3 5VP-P
-6 2VP-P
-9
-12 1M
10M
100M
FREQUENCY (Hz)
FIGURE 7. LARGE SIGNAL FREQUENCY RESPONSE
1G
-30
5VOP-P-DIFF
-40 100Ω RLOAD
-50
-60 THD
-70
-80 3rd HD
-90 2nd HD
-100
1M
10M
FREQUENCY (Hz)
100M
FIGURE 8. HARMONIC DISTORTION vs FREQUENCY
-40
-45 100Ω RLOAD
-50
-55
-60
THD
-65
-70
-75
-80 2nd HD
-85 3rd HD
-90
1
10
VOP-P-LOAD (V)
FIGURE 9. 4MHz HARMONIC DISTORTION vs OUTPUT VOLTAGE
5 FN6795.0
March 16, 2012
5 Page 
ISL1550
Applications Information
Product Description
The ISL1550 is a dual operational amplifier designed for line driving
in DMT VDSL2 8MHz, 12MHz, 17MHz and 30MHz bandplans
solutions. It is a current mode feedback amplifier with low distortion
drawing moderately low supply current. Due to the current feedback
architecture, the ISL1550 closed-loop 3dB bandwidth is dependent
on the value of the feedback resistor. First, the desired bandwidth is
selected by choosing the feedback resistor, RF, and then the gain is
set by picking the gain resistor, RG (Figure 3).
VDSL CO Applications
The ISL1550 is designed as a VDSL line driver for CO. At an
output current of ±450mA, the typical supply voltage headroom
is 1.5V on each side of the differential output.
The average line power requirement for the VDSL CO application
is 20dBm (100mW) into a 100Ω line. The average line voltage is
3.16VRMS. The VDSL DMT peak-to-average ratio (crest factor) of
5.3 implies peak voltage of 16.8VP into the line. Using a
differential drive configuration and transformer coupling with
standard back termination, a transformer ratio of 1:2.5 is
selected. The active termination technique provides better power
efficiency by reducing the backmatch resistor by a factor of
K = 5. Positive feedback resistors, RP, can be sized to make the
effective backmatch impedance larger. The circuit configuration
is shown in Figure 35.
+
-
750Ω
12.5/k
RP
TX1
AFE
1.5kΩ
750Ω
-
+
RPΩ
12.5/k
1:2.5
100
RP = RF(K/(K-1))
FIGURE 35. CIRCUIT CONFIGURATION
Power Supply Bypassing and Printed Circuit
Board Layout
As with any high frequency device, good printed circuit board
layout is necessary for optimum performance. Ground plane
construction is highly recommended. Lead lengths should be as
short as possible (below 0.25”). The power supply pins must be
well bypassed to reduce the risk of oscillation. A 4.7µF tantalum
capacitor in parallel with a 0.1µF ceramic capacitor is adequate
for each supply pin. During power-up, it is necessary to limit the
slew rate of the rising power supply to less than 1V/µs. If the
power supply rising time is undetermined, a series 10Ω resistor
on the power supply line before the decoupling caps can be used
to ensure the proper power supply rise time.
For good AC performance, parasitic capacitances should be kept
to a minimum, especially at the inverting input. This implies
keeping the ground plane away from this pin. Carbon or metal
film resistors are acceptable, while use of wire-wound resistors
should be avoided because of their parasitic inductance.
Similarly, capacitors should be low inductance for best
performance.
Capacitance at the Inverting Input
Due to the topology of the current feedback amplifier, stray
capacitance at the inverting input will affect the AC and transient
performance of the ISL1550 when operating in the non-inverting
configuration.
Feedback Resistor Values
The ISL1550 has been designed and specified with RF = 1.5kΩ
for AV = +5 (Figure 3). As is the case with all current feedback
amplifiers, wider bandwidth at the expense of slight peaking, can
be obtained by reducing the value of the feedback resistor.
Inversely, larger values of the feedback resistor will cause rolloff
to occur at a lower frequency.
Quiescent Current vs Temperature
The ISL1550 was designed to slightly increase quiescent current
with temperature to maintain good distortion performance at
high temperatures. Refer to “Typical Performance Curves”
beginning on page 5.
Supply Voltage Range
The ISL1550 has been designed to operate with supply voltages
from ±4.0V to ±6.6V nominal. Optimum bandwidth, slew rate,
and video characteristics are obtained at higher supply voltages.
Single Supply Operation
If a single supply is desired, values from +8.0V to +13.2V
nominal can be used as long as the input common mode range
is not exceeded. When using a single supply, be sure to either,
1. DC bias the inputs at an appropriate common mode voltage
and AC-couple the signal, or
2. Ensure the driving signal is within the common mode range of
the ISL1550.
11 FN6795.0
March 16, 2012
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet ISL1550.PDF ] | |
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