LTC5532
13
5532f
APPLICATIO S I FOR ATIO
WUUU
Figure 2. Mobile Phone Tx Power Control Application Diagram with a Capacitive Tap
Applications
The LTC5532 can be used as a self-standing signal strength
measuring receiver for a wide range of input signals from
–32dBm to 10dBm for frequencies from 300MHz to 7GHz.
Operation at higher frequencies, to 12GHz or above, is
achievable with reduced performance. The smaller DFN
package version is recommended for these applications
because of its lower parasitics. Figure 1 plots the output
voltage as a function of RF power of a 12GHz CW input
signal.
The LTC5532 can be used as a demodulator for AM and
ASK modulated signals with data rates up to 2MHz.
Depending on specific application needs, the RSSI output
can be split between two branches, providing AC-coupled
data (or audio) output and DC-coupled RSSI output for
signal strength measurements and AGC.
The LTC5532 can be used for RF power detection and
control. Figure 2 is an example of a transmitter power
controller, using the LTC5532 with a capacitive tap to the
power amplifier. A 0.5pF capacitor (C1) followed by a
200Ω resistor (R1) form a coupling circuit with about
20dB loss at 900MHz referenced to the LTC5532 RF input
pin. In the actual product implementation, component
values for the capacitive tap may be different depending on
parts placement, PCB parasitics and parameters of the
antenna.
The LTC5532 can be configured as a comparator for RF
power detection and RF power alarms. The characteriza-
tion data includes a plot of the LTC5532 output delay in
response to a positive input step of varying RF level.
RF
IN
GND
V
OS
V
CC
V
OUT
V
M
LTC5532ES6
1
2
3
6
5
4
0.1µF
R2
R3
5532 F02
Li-Ion
CELL BAND
PCS BAND
VPC
MOBILE
PHONE
DSP
OFFSET
ADJUSTMENT
DIPLEXER
TX PA
MODULE
R1
200Ω
1%
C1
0.5pF
±0.05pF
BSE
RF INPUT POWER (dBm)
–32
0
V
OUT
OUTPUT VOLTAGE (mV)
400
1200
1600
2000
–8 –4 0 4
3600
5532 F01
800
–28 –24 –20 –16 –12 8
2400
2800
3200
T
A
= 25°C
Figure 1. Typical Detector Characteristics,
12GHz, Gain = 2, V
OS
= 0V (DFN Package)
