Circuit Note

CN-0187

Circuits from the Lab™ reference circuits are engineered and

tested for quick and easysystemintegrationto helpsolve today’s

analog, mixed-signal, and RF design challenges. For more

informationand/orsupport,visitwww.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

Rev.0

Circuitsfromthe Lab™circuitsfromAnalog Deviceshave been designedandbuiltbyAnalogDevices

engineers. Standard engineering practices have been employed in the design and construction of

eachcircuit,andtheirfunctionandperformancehavebeentestedandverifiedinalabenvironmentat

room temperature. However, you are solely responsible for testing the circuit and determining its

suitabilityandapplicabilityforyouruseandapplication.Accordingly,innoeventshallAnalogDevices

be liable for direct, indirect, special, incidental, consequential or punitive damages due to any cause

whatsoeverconnectedtotheuseofanyCircuitsfromtheLabcircuits. (Continuedonlastpage)

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781.329.4700

www.analog.com

Fax: 781.461.3113

©2011 Analog Devices, Inc. All rights reserved.

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.

U3-A

U3-D

U1

COMM

ENBL

VA1

VA2

VB1

VB2

0.47µF

27Ω

27Ω

27Ω

AGND

DGND

10kΩ

10kΩ

0.47µF

220Ω

220Ω

220Ω

442Ω

75Ω

+3.3V

+3.3V

0.01µF

0.01µF

RFIN

0.01µF

0.1µF

1000pF

+3.3V

+3.3V

AVDD DVDD

VDRIVE

CS

DOUTA

SCLK

ADP121

ADL5502

AD7266

+5.5V

+3.3V

1µF

VIN

FLTR

VPOS

RFIN

VRMS

PEAK

CNTL

VOUT

EN

GND

1µF

SDP

BOARD

AND

SUPPORT

CIRCUITS

NOTE: U2 AND U3 ARE ADA4891-4

CONTROL

(HIGH RESET;

LOW PEAK HOLD)

U5

U6

+1.25V

+1.25V

+2.5V

*

*

*

*

*SEE TEXT

8

4

1

2

3

7

6

5

U2-B

U3-B

27Ω

U2-D

10kΩ

10kΩ

0.47µF

220Ω

220Ω

220Ω

442Ω

+3.3V

U3-D

U3-A

0.47µF

+2.5V

U2-A

U2-C

U3-C

Figure 1. High Speed, Low Power, Crest Factor, Peak, and RMS Power Measurement System (Simplified Schematic: All connections and Decoupling Not Shown)