450 MHz to 6000 MHz

Crest Factor Detector

ADL5502

Rev. A

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FEATURES

True rms response detector

Envelope peak hold output

Excellent temperature stability

±0.25 dB rms detection accuracy vs. temperature

±0.25 dB envelope detection accuracy vs. temperature;

over the top 25 dB of the input range

Over 35 dB input power dynamic range, inclusive of crest factor

RF bandwidths from 450 MHz to 6 GHz

Envelope bandwidths of 10 MHz

500 Ω input impedance

Single-supply operation: 2.5 V to 3.3 V

Low power: 3 mA at 3 V supply

RoHS-compliant part

APPLICATIONS

Power and envelope measurement of W-CDMA, CDMA2000,

and QPSK-/QAM-based OFDM, and other complex

modulation waveforms

RF transmitter or receiver power and envelope measurement

FUNCTIONAL BLOCK DIAGRAM

COMM

RFIN

ENBL

RMS CORE

BUFFERS

100Ω

1kΩ

4nF

PEAK/

ENVELOPE

100Ω

VRMS

PEAK

CNTL

VPOS

FLTR

ADL5502

INTERNAL

FILTERING

Figure 1.

1µs/DIV

PEAK

VRMS

CNTL

PEAK HOLD

ENV TRACK

RF INPUT

Figure 2.

GENERAL DESCRIPTION

The ADL5502 is a mean-responding (true rms) power detector

in combination with an envelope detector to accurately determine

the crest factor of a modulated signal. It can be used in high

frequency receiver and transmitter signal chains from 450 MHz

to 6 GHz with envelope bandwidths over 10 MHz. Requiring

only a single supply between 2.5 V and 3.3 V, the detector draws

less than 3 mA. The input is internally ac-coupled and has a

nominal input impedance of 500 Ω.

The rms output is a linear-responding dc voltage with a conversion

gain of 1.8 V/V rms at 900 MHz. The peak envelope output with a

conversion gain of 1.2 V/V is toggled for peak hold with less

than 1% output voltage droop in over 1 ms.

The ADL5502 is a highly accurate, easy to use means of

determining the rms and peak to the average value of complex

waveforms. It can be used for crest factor measurements of both

simple and complex waveforms but is particularly useful for

measuring high crest factor (high peak-to-rms ratio) signals,

such as W-CDMA, CDMA2000, and QPSK-/QAM-based

OFDM waveforms. The peak hold function allows the capture

of short peaks in the envelope with lower sampling rate ADCs.

The crest factor detector operates from −40°C to +85°C and is

available in an 8-ball, 1.5 mm × 1.5 mm wafer-level chip scale