LTC5582 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC5582' PDF : 16 Pages View PDF
LTC5582
Applications Information
The LTC5582 is a true RMS RF power detector, capable
of measuring an RF signal over the frequency range from
40MHz to 10GHz, independent of input waveforms with
different crest factors such as CW, CDMA2K, WCDMA,
LTE and WiMAX signals. Up to 60dB dynamic range is
achieved with a very stable output within the full tem-
perature range from –40°C to 85°C. Its sensitivity can be
as low as –57dBm up to 2.7GHz even with single-ended
50Ω input termination.
RF Inputs
The differential RF inputs are internally biased at 1.585V.
The differential impedance is 400Ω. These pins should be
DC blocked when connected to ground or other matching
components.
The LTC5582 can be driven in a single-ended configuration
as illustrated in Figure 3. The single-ended input impedance
vs frequency is detailed in Table 1. The DEC Pin can be
either left floating or AC-coupled to ground via an external
capacitor. While the RF signal is applied to the IN+ (or IN–)
Pin, the other pin IN– (or IN+) should be AC-coupled to
ground. By simply terminating a 68Ω resistor between the
IN+ and IN– Pins and coupling the non-signal side to ground
using a 1nF capacitor, broadband 50Ω input matching can
be achieved with typical return loss better than 10dB from
40MHz to 5.5GHz. At higher RF frequencies, additional
matching components may be needed.
J1
C4
RF INPUT
1nF
C5
R4
68Ω
C9
OPTIONAL
LTC5582
IN+
2
DEC
3
IN–
4
C8
1nF
VCC
200Ω
50pF
200Ω
5582 F03
Figure 3. Single-Ended Input Configuration
10
Table 1. Single-Ended Input Impedance (DEC Floating)
FREQUENCY
(MHZ)
INPUT IMPEDANCE
(Ω)
S11
MAG
ANGLE (˚)
40
220.7-j63.0
0.655
–7.0
100
195.2-j47.3
0.611
–7.1
200
175.1-j37.6
0.571
–7.3
400
200.9-j42.2
0.618
–6.3
600
159.8-j52.9
0.563
–11.5
800
154.8-j52.4
0.554
–12.2
1000
158.6-j57.1
0.568
–12.4
1200
164.1-j81.1
0.612
–14.7
1400
138.1-j110.5
0.650
–21.0
1600
102.7-j113.3
0.659
–28.5
1800
80.1-j103.1
0.647
–35.3
2000
67.1-j92.0
0.628
–41.3
2200
58.4-j82.3
0.607
–46.7
2400
52.9-j74.5
0.586
–52.0
2600
48.5-j67.6
0.566
–57.0
2800
44.8-j61.5
0.546
–62.0
3000
41.8-j56.1
0.526
–66.9
3200
41.8-j56.3
0.508
–72.0
3400
37.3-j47.0
0.490
–77.1
3600
35.4-j42.9
0.473
–80.2
3800
33.9-j39.1
0.457
–87.7
4000
32.4-j35.5
0.445
–93.1
4200
31.1-j32.3
0.429
–98.8
4400
29.9-j29.1
0.416
–104.7
4600
28.9-j26.2
0.405
–110.7
4800
27.9-j23.3
0.395
–117.0
5000
27.0-j20.5
0.388
–123.5
5200
26.2-j17.8
0.382
–130.2
5400
25.4-j15.2
0.376
–136.9
5600
24.7-j12.6
0.376
–144.1
5800
24.0-j10.0
0.377
–151.3
6000
23.3-j7.5
0.377
–158.4
The LTC5582 differential inputs can also be driven from
a fully balanced source as shown in Figure 4. When the
signal source is a single-ended 50Ω, conversion to a dif-
ferential signal can be achieved using a 1:8 balun to match
the internal 400Ω input impedance to the 50Ω source.
This impedance transformation results in 9dB voltage
gain, thus 9dB improvement in sensitivity is obtained
5582f
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