CN-0187 Datasheet, PDF (1/7 Pages) Analog Devices – Crest Factor, Peak, and RMS RF Power Measurement Circuit Optimized for High Speed, Low Power, and Single 3.3 V Supply

Circuit Note
CN-0187
Circuits from the Lab™ reference circuits are engineered and
tested for quick and easy system integration to help solve today’s
analog, mixed-signal, and RF design challenges. For more
information and/or support, visit www.analog.com/CN0187.
Devices Connected/Referenced
ADL5502 450 MHz to 6 GHz Crest Factor Detector
AD7266
Differential/Single-Ended Input, Dual,
Simultaneous Sampling, 2 MSPS, 12-Bit,
3-Channel SAR Analog-to-Digital Converter
ADA4891-4
Low Cost, Quad, CMOS, High Speed, Rail-to-
Rail Amplifier
ADP121
150 mA, Low Quiescent Current, CMOS Linear
Regulator in 5-Lead TSOT or 4-Ball WLCSP
Crest Factor, Peak, and RMS RF Power Measurement Circuit Optimized for
High Speed, Low Power, and Single 3.3 V Supply
EVALUATION AND DESIGN SUPPORT
Circuit Evaluation Boards
CN-0187 Circuit Evaluation Board (EVAL-CN0187-SDPZ)
System Demonstration Platform (EVAL-SDP-CB1Z)
Design and Integration Files
Schematics, Layout Files, Bill of Materials
CIRCUIT FUNCTION AND BENEFITS
The circuit shown in Figure 1 measures peak and rms power
at any RF frequency from 450 MHz to 6 GHz over a range of
approximately 45 dB. The measurement results are converted
to differential signals in order to eliminate noise and are
provided as digital codes at the output of a 12-bit SAR ADC
with serial interface and integrated reference. A simple two-
point calibration is performed in the digital domain.
+3.3V
*SEE TEXT
1000pF 0.1µF
8
C_FLTR*
ENBL
1
0.01µF
FLTR _U1 VRMS
ADL5502
7
2 VPOS
PEAK 6
0.01µF
RFIN
0.01µF
3 RFIN
CNTL 5
COMM
75Ω
4
U2-B
*
*
*
*
U3-B
CONTROL
(HIGH RESET;
LOW PEAK HOLD)
NOTE: U2 AND U3 ARE ADA4891-4
442Ω
220Ω
+3.3V
U2-A
220Ω
220Ω
+1.25V ^U2-D
10kΩ
0.47µF
10kΩ
+5.5V
1µF
VIN VOUT
U5
ADP121
EN
GND
+3.3V
1µF
442Ω
220Ω
+3.3V
UU33--AA
220Ω
220Ω
+1.25V ^UU33--DD
10kΩ
0.47µF
10kΩ
+3.3V +3.3V
27Ω
27Ω
+2.5V
U2-C
0.47µF
AVDD DVDD
VA1
U6
AD7266
VDRIVE
VA2
D_CAPA
CS
DOUTA
SCLK
27Ω
VB1
27Ω
+2.5V
U3-C
VB2
D_CAPB
AGND DGND
0.47µF
SDP
BOARD
AND
SUPPORT
CIRCUITS
Figure 1. High Speed, Low Power, Crest Factor, Peak, and RMS Power Measurement System (Simplified Schematic: All connections and Decoupling Not Shown)
Rev.0
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