lt5534 Linear Technology Corporation, lt5534 Datasheet - Page 7

• Manufacturer Part Number: lt5534
• Description: 50mhz To 3ghz Rf Power Detector With 60db Dynamic Range
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
Table 1. RF Input Impedance
need. By simply inserting an attenuator in front of the RF
input, the power range is shifted higher by the amount of
the attenuation. Moreover, due to the high RF input
impedance of the LT5534, the detecting range can be
moved downward for better detection sensitivity by using
a narrow band L-C matching network. By this means, the
sensitivity of the detector can be extended to as low as –
75dBm. By changing the value of resistor R1, the sensi-
tivity of the detector can be fine-tuned within the range
from –75dBm to –62dBm. Though the range is adjust-
able, the overall linear dynamic range remains the same.
Output Interface
The output interface of the LT5534 is shown in Figure 4. The
output currents from the RF detectors are summed and
converted into an output voltage, V
charging current available to the output load is about 200µA.
The internal compensation capacitor C
tee stable operation for a large capacitive output load. The
slew rate is 133V/µs, and the small-signal output bandwidth
is approximately 30MHz when the output is resistively
FREQUENCY
(MHz)
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
100
200
400
600
800
50
IMPEDANCE (Ω)
U
1429-j429
18.5-j96.2
16.6-j85.0
15.2-j75.7
13.7-j67.5
12.1-j60.1
96.8-j278
67.6-j229
49.7-j193
38.4-j165
30.8-j143
25.4-j125
21.4-j109
947-j710
509-j609
250-j440
149-j344
INPUT
U
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
W
0.938
0.934
0.922
0.908
0.900
0.896
0.893
0.889
0.883
0.879
0.873
0.866
0.862
0.848
0.834
0.826
0.822
MAG
OUT
C
is used to guaran-
. The maximum
S11
ANGLE (DEG)
U
–14.1
–18.3
–22.7
–27.3
–32.3
–37.3
–42.6
–48.0
–53.6
–59.6
–65.6
–71.8
–78.2
–1.1
–2.9
–5.6
–9.9
terminated or open. The fastest output transient response
is achieved when a large signal is applied to the RF input
port. See the output transient response plot in the Typical
Performance Characteristics section.
When the output is terminated with a load capacitance
C
example, the slew rate is reduced to 17.4V/µs when C
10pF. A capacitive load may result in output voltage
overshoot, which can be minimized with a series compen-
sation resistor R2 as shown in Figure 1. The suggested
resistor values for various capacitive loads are listed in
Table 2.
Table 2. Resistor Value for Capacitive Output
The optional RC network at the output (R2 and C5 on the
demo board) can also provide further output filtering, if
needed. The output bandwidth is primarily dictated by the
RC constant of this lowpass filter when its corner fre-
quency is less than 30MHz.
When a large signal (e.g., –2dBm) is present at the RF
input port, the output voltage swing can be as high as 2.4V.
To assure proper operation of the chip, the minimum
resistive load at the output termination should be greater
than 18kΩ.
L
, the slew rate is then limited to 200µA/(C
V
CC
FROM RF DETECTORS
OUTPUT CURRENTS
C5 (pF)
Figure 4. Simplified Circuit Schematic
of the Output Interface
1.5
10
20
5
–
+
C
C
+
R2 (kΩ)
200µA
2.5
5
4
2
5534 F04
L
+ 1.5pF). For
LT5534
V
OUT
5534fa
7
L
=