LTC5532

13

5532f

APPLICATIO S I FOR ATIO

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

200

Ω 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.

GND

LTC5532ES6

1

2

3

6

5

4

0.1

µF

R2

R3

5532 F02

Li-Ion

CELL BAND

PCS BAND

VPC

MOBILE

PHONE

DSP

OFFSET

ADJUSTMENT

DIPLEXER

TX PA

MODULE

R1

200

Ω

1%

C1

0.5pF

±0.05pF

BSE

RF INPUT POWER (dBm)

–32

0

400

1200

1600

2000

–8 –4

0

4

3600

5532 F01

800

–28 –24 –20 –16 –12

8

2400

2800

3200

Figure 1. Typical Detector Characteristics,