50 MHz to 6 GHz

TruPwr Detector

ADL5501

Rev. B

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FEATURES

True rms response

Excellent temperature stability

Up to 30 dB input dynamic range

50 Ω input impedance

1.25 V rms, 15 dBm, maximum input

Single-supply operation: 2.7 V to 5.5 V

Low power: 3.3 mW at 3 V supply

RoHS-compliant

APPLICATIONS

Measurement of CDMA-, CDMA2000-, W-CDMA-, and QPSK-/

QAM-based OFDM, and other complex modulation

waveforms

RF transmitter or receiver power measurement

5

0.03

0.1

1

–25

–20

–15

–10

–5

0

5

10

15

INPUT (dBm)

Figure 1. Output vs. Input Level, Supply = 3 V, Frequency = 1.9 GHz

GENERAL DESCRIPTION

The ADL5501 is a mean-responding TruPwr™ power detector

for use in high frequency receiver and transmitter signal chains

from 50 MHz to 6 GHz. It is easy to apply, requiring only a single

supply between 2.7 V and 5.5 V and a power supply decoupling

capacitor. The input is internally ac-coupled and has a nominal

input impedance of 50 Ω. The output is a linear-responding dc

voltage with a conversion gain of 6.3 V/V rms at 900 MHz.

The ADL5501 is intended for true power measurement of simple

and complex waveforms. The device is particularly useful for

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

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

based OFDM waveforms. The on-chip modulation filter provides

adequate averaging for most waveforms.

The on-chip, 100 Ω series resistance at the output, combined

with an external shunt capacitor, creates a low-pass filter response

that reduces the residual ripple in the dc output voltage. For more

complex waveforms, an external capacitor at the FLTR pin can

be used for supplementary signal demodulation.

The ADL5501 offers excellent temperature stability across a

30 dB range and near 0 dB measurement error across temperature

over the top portion of the dynamic range. In addition to its

temperature stability, the ADL5501 offers low process variations

that further reduce calibration complexity.

The ADL5501 operates from −40°C to +85°C and is available in

a small 6-lead SC-70 package. It is fabricated on a proprietary

high fT silicon bipolar process.

FUNCTIONAL BLOCK DIAGRAM

RFIN

BUFFER

VPOS

VRMS

COMM

ERROR

AMP

x2

x2

i

i

TRANS-

CONDICTANCE

CELLS

ADL5501

100Ω

FLTR

BAND-GAP

REFERENCE

ENBL

INTERNAL FILTER

CAPACITOR

Figure 2.