50 MHz to 4 GHz
TruPwr™ Detector
ADL5501
5
1
FEATURES
True rms response
Excellent temperature stability
Up to 30 dB input dynamic range at 4 GHz
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
0.1
APPLICATIONS
Measurement of CDMA2000-, W-CDMA-, and QPSK-/QAM-
based OFDM, and other complex modulation waveforms
RF transmitter or receiver power measurement
0.03
–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 power detector for use
in high frequency receiver and transmitter signal chains from
50 MHz to 4 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 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 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 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
VPOS
FLTR
ADL5501
INTERNAL FILTER
CAPACITOR
i
2
x
RFIN
TRANS-
CONDICTANCE
CELLS
ERROR
AMP
i
2
x
BUFFER
VRMS
100Ω
BAND-GAP
REFERENCE
ENBL
COMM
Figure 2.
Rev. 0
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