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PDF ISL55211 Data sheet ( Hoja de datos )
| Número de pieza | ISL55211 | |
| Descripción | Differential Amplifier | |
| Fabricantes | Intersil | |
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Wideband, Low Noise, Low Distortion, Fixed Gain,
Differential Amplifier
ISL55211
The ISL55211 is a wideband, differential input to differential
output amplifier offering 3 possible internal gain settings.
Using fixed 500Ω internal feedback resistors, the amplifier
may be configured for a differential gain of 2, 4 or 5V/V
depending on which combination of input pins are connected
to the signal source. Internal feedback capacitors controls the
signal bandwidth to be a constant 1.4GHz in all gain settings.
Ideally suited for AC-coupled data acquisition applications, the
output DC common mode voltage is controlled through an
external VCM pin or left to default to 1.2V above the negative
supply pin. Where the differential signal source is AC-coupled,
the input common mode voltage will equal the output
common mode voltage.
Intended for very high dynamic range ADC interface
applications, the ISL55211 offers 5600V/µs differential slew
rate, <12nV/√Hz output noise, and >100dBc SFDR to
>100MHz for 2VP-P 2-tone 3rd order intermodulation. Its
balanced architecture effectively suppresses even order
distortion terms - an important issue for very wide band 1st
Nyquist zone ADC interface applications. Minimum gain
operation of 2V/V (6dB) with <1dB peaking ensures stable
performance over-temperature. It's ultra high differential slew
rate of 5600V/µs provides adequate performance margin for
large signal application through 500MHz.
The ISL55211 requires only a single 3.3V (max. 4.2V) power
supply and 35mA quiescent current, providing a very low
power solution (115mW). Further power savings are possible
using the optional power shutdown control - where the
quiescent current can be reduced to <0.4mA. A companion
device, the ISL55210, offers similar performance where the
feedback and gain resistors are external. Both are available in
a 16 Ld TQFN (Pb-free) package and are specified for
operation over the -40°C to +85°C ambient temperature
range.
Features
• 3 Fixed Gain Options . . . . . . . . . . . . . . . . . . . . . . . 2, 4, or 5V/V
• Constant Bandwidth Over Gain . . . . . . . . . . . . . . . . . . 1.4GHz
• Differential Slew Rate . . . . . . . . . . . . . . . . . . . . . . . 5,600V/µs
• 2VP-P, 2-tone IM3 (200Ω) 100MHz . . . . . . . . . . . . . . -103dBc
• Low Differential Output Noise (Gain 5V/V) . . . . . . <12nV/√Hz
• Supply Voltage Range . . . . . . . . . . . . . . . . . . . . . . 3.0V to 4.2V
• Quiescent Power (3.3V Supply) . . . . . . . . . . . . . . . . . .115mW
Applications
• Low Power, High Dynamic Range ADC Interface
• Differential Mixer Output Amplifier
• SAW Filter Pre/Post Driver
• Fixed Gain Coax Receiver
Related Devices
• ISL55210 - External Gain Set Version
• ISLA112P50 - 12-bit, 500MSPS ADC (<500mW)
• ISLA214P50 - 14-bit, 500MSPS ADC (<850mW)
Related Literature
• AN1649 - “Designer’s guide to the ISL55210 and ISL55211
Evaluation Boards”
+3.3V
Vi 1:2
50
VCM
1.2V
ADT4-1T
35mA
(115mW)
+
ISL55211
G= 5V/V
10 ADT2-1T50
1:1.4
22pF
120nH
VADC
ISLA214P50
(850mW)
14Bit 500MSPS
300 8pF
180mVP-P
For ADC-1dBFS
120nH
- 10 50
VCM
20
logVADC
Vi
=
20dB
HIGHGAIN, VERYLOWPOWER, ADCINTERFACEWITH3RD ORDEROUTPUTFILTER
23
20
17
14
11
8
5
2
-1
-4
-7
-10
-13
1M
MEASURED FREQUENCY RESPONSE
10M
100M
FREQUENCY (Hz)
FIGURE 1. TYPICAL APPLICATION CIRCUIT
1G
June 21, 2011
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
FN7868.0
1-888-INTERSIL or 1-888-468-3774 |Copyright Intersil Americas Inc. 2011. All Rights Reserved
Intersil (and design) and FemtoCharge are trademarks owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
1 page  
ISL55211
Electrical Specifications VS+ = +3.3V Test Conditions: G = 12dB, VCM = open, VO = 2VP-P, RL = 200Ω differential, TA = +25°C,
differential input, differential output, input and output referenced to internal default VCM (1.2V nominal) unless otherwise specified. (Continued)
PARAMETER
CONDITIONS
MIN MAX
(Note 6) TYP (Note 6) UNIT TESTED
Power-down Quiescent Current
Input Bias Current
TA = +25°C
TA = -40°C to +85°C
PD = 0V, current positive into pin
0.2 0.3 0.4 mA
0.15
0.45
mA
-5 1 +5 µA
*
Input Impedance
2 || 5
MΩ || pF
Turn-on Time Delay
Measured to output on
200 ns
Turn-off Time Delay
Measured to output off
400 ns
NOTE:
6. Compliance to datasheet limits is assured by one or more methods: production test, characterization, and/or design.
VI
50
INPUT
1:n
RT
ISL55211
500
RG
+
-
RG
500
TABLE 1. ISL55211 INTENDED TRANSFORMER + INTERNAL GAIN
SETTINGS
INPUT
XFMR
TURNS
RATIO
1:1.4
INTERNAL
RG VALUE
(Ω)
250
GAIN (V/V)
VO/VI
2.8
GAIN (dB)
VO/VI
9
RT VALUE (Ω)
TO GET 50Ω
MATCH
122
VO
1:1.4
125
5.6
15 162
1:1.4
100
7
17 192
1:2 250
4
12 333
1:2 125
8
18 1020
1:2 100
10
20 Open
FIGURE 2. INTENDED CONFIGURATION
5 FN7868.0
June 21, 2011
5 Page 
ISL55211
+3.3V
115mW 35mA
10k
500 PD
50
1:1.4
Vi 1µF
RT
ADT2-
1T
or
ADT4-
1Wt
+
RG
200
VCM
0.1µF
-
RG
0.2pF
0.2pF
85
1µF 35
VO
35
1µF 85
50
1:1
1µF Vm
ADT1-
1WT
500
ISL55211
FIGURE 29. TEST CIRCUIT 1
Working with a transformer coupled input as shown in Figure 29,
or with two DC blocking caps from a differential source, means
the output common mode voltage set by either the default
internal VCM setting, or a voltage applied to the VCM control pin,
will also appear as the input common mode voltage. This
provides a very easy way to control the ISL55211 I/O common
mode operating voltages for an AC-coupled signal path. The
internal common mode loop holds the output pins to VCM and,
since there is no DC path for an ICM current back towards the
input in Figure 29, that VCM setting will also appear as the input
common mode voltage. It is useful, for this reason, to leave any
input transformer secondary centertap unconnected. The
internally set VCM voltage is referenced from the negative supply
pin. With a single 3.3V supply, it is very close to 1.2V but will
change with total supply voltage across the device as shown in
Figure 27.
Most of the characterization curves starting with Figure 29 then
get different gains by changing the connections to the two pairs
of input RG connections, as shown on the pin configuration
drawing on page 2. Two input turns ratios are intended for Test
Circuit 1; either a 1:1.4 turns ratio (ohms ratio of 2) or a 1:2 turns
ratio (ohm ratio of 4). The specific transformers shown in
Figure 29 are representative of broadband RF transformers but
alternate devices and manufacturers of these turns ratio devices
are certainly applicable. The output side of this test circuit
presents a differential 200Ω load while converting the
differential to single-ended through a resistive attenuator and a
1:1 transformer. This inserts approximately a 17dB insertion loss
that is removed to report the characteristic curves. For load tests
below the 200Ω shown in Figure 29, a simple added shunt
resistor is placed across the output pins. For loads > 200Ω, the
series and shunt load R's are adjusted to show that total load
(including the 50Ω measurement load reflected through the 1:1
output measurement port transformer) and provide an apparent
50Ω differential source to that transformer. This output side
transformer is for measurement purposes only and is not
necessary for final applications circuits. There are output
interface designs that do benefit from a transformer as part of
the signal path as shown in Figure 1. In that case, the 1:1:4
output side transformer becomes part of a filter design and
recovers the filter insertion loss from the amplifier output pins to
the ADC inputs.
Where just the amplifier is tested, a 4-port network analyzer is
used and the very simple test circuit of Figure 30 is
implemented. This is used to measure the differential S21 curves
vs gain of Figure 17 and as a simulation circuit for the differential
output impedance vs gain of Figure 18. Changing the gain is a
simple matter of adjusting the connections to the four input RG
connections resistors, as shown in Table 1. This circuit depends
on the two AC-coupled source 50Ω of the 4 port network analyzer
and presents an AC-coupled differential 100Ω load to the
amplifier as the input impedance of the remaining two ports of
the network analyzer.
+3.3V
10k
RF PD
50
1/2 of a 4-port
S-parameter
RG
+
VCM
RT
50
1/2 of a 4-port
S-parameter
-
50 RG
50
RF ISL55211
FIGURE 30. TEST CIRCUIT 2 4-PORT S-PARAMETER
MEASUREMENTS
Using this measurement allows the small single bandwidth of
just the ISL55211 to be exposed. Many of the other
measurements are using I/O transformers that are limiting the
apparent bandwidth to a reduced level. Figure 17 shows the 3
normalized differential S21 curves for the possible internal gains
of 9dB, 14dB and 15dB. The small signal bandwidth is remaining
nearly constant at 1.4GHz due to the internal capacitive
feedback network.
The closed loop differential output impedance of Figure 18 is
simulated using Figure 30 in ADS. This shows a relatively low
output impedance (< 1Ω through 100MHz) constant with signal
gain setting. Typical FDA outputs show a closed loop output
impedance that increases with signal gain setting. The ISL55211
holds a more constant response due to internal design elements
unique to this device.
Common mode output measurements are made using the circuit
in Figure 31. Here, the outputs are summed together through two
100Ω resistors (still a 200Ω differential load) to a center point
where the average, or common mode, output voltage may be
sensed. This is coupled through a 1µF DC blocking capacitor and
measured using 50Ω test equipment. The common mode source
impedance for this circuit is the parallel combination of the
2-100Ω elements, or 50Ω. Figure 19 uses this circuit to measure
the small and large signal response from the VCM control pin to
the output common mode. This pin includes an internal 50pF
capacitor on the default bias network (to filter supply noise when
there is no connection to this pin), which bandlimits the response
to approximately 30MHz. This is far lower than the actual
bandwidth of the common mode loop. Figure 20 uses this output
11 FN7868.0
June 21, 2011
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| PDF Descargar | [ Datasheet ISL55211.PDF ] | |
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