500 MHz, Linear-in-dB VGA with AGC Detector AD8367 FEATURES FUNCTIONAL BLOCK DIAGRAM VPSI VPSO ENBL Broad-range analog variable gain: 2.5 dB to +42.5 dB 12 11 2 3 dB cutoff frequency of 500 MHz AD8367 ICOM 1 14 ICOM Gain up and gain down modes INPT 3 9-STAGE ATTENUATOR BY 5dB BIAS 9 DECL Linear-in-dB, scaled 20 mV/dB 13 HPFL Resistive ground referenced input g m 10 VOUT CELLS Nominal Z = 200 IN On-chip, square-law detector SQUARE GAUSSIAN INTERPOLATOR LAW Single-supply operation: 2.7 V to 5.5 V DETECTOR ICOM 7 8 OCOM APPLICATIONS 4 5 6 MODE GAIN DETO Cellular base stations Figure 1. Broadband access Power amplifier control loops Complete, linear IF AGC amplifiers High speed data I/O GENERAL DESCRIPTION The AD8367 is a high performance 45 dB variable gain The analog gain-control input is scaled at 20 mV/dB and runs amplifier with linear-in-dB gain control for use from low from 50 mV to 950 mV. This corresponds to a gain of 2.5 dB frequencies up to several hundred megahertz. The range, to +42.5 dB, respectively, when the gain up mode is selected and flatness, and accuracy of the gain response are achieved using +42.5 dB to 2.5 dB, respectively, when gain down mode is Analog Devices X-AMP architecture, the most recent in a selected. The gain down, or inverse, mode must be selected series of powerful proprietary concepts for variable gain when operating in AGC in which an integrated square-law applications, which far surpasses what can be achieved using detector with an internal setpoint is used to level the output to competing techniques. 354 mV rms, regardless of the crest factor of the output signal. A single external capacitor sets up the loop averaging time. The input is applied to a 9-stage, 200 resistive ladder network. Each stage has 5 dB of loss, giving a total attenuation of 45 dB. The AD8367 can be powered on or off by a voltage applied to At maximum gain, the first tap is selected at progressively the ENBL pin. When this voltage is at a logic LO, the total lower gains, the tap moves smoothly and continuously toward power dissipation drops to the milliwatt range. For a logic HI, higher attenuation values. The attenuator is followed by a the chip powers up rapidly to its normal quiescent current of 42.5 dB fixed gain feedback amplifieressentially an 26 mA at 25C. The AD8367 is available in a 14-lead TSSOP operational amplifier with a gain bandwidth product of package for the industrial temperature range of 40C to +85C. 100 GHzand is very linear, even at high frequencies. The output third order intercept is +20 dBV at 100 MHz (+27 dBm, re 200 ), measured at an output level of 1 V p-p with VS = 5 V. Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 02710-001AD8367 TABLE OF CONTENTS Features .............................................................................................. 1 Noise and Distortion.................................................................. 12 Applications....................................................................................... 1 Output Centering ....................................................................... 12 Functional Block Diagram .............................................................. 1 RMS Detection ........................................................................... 13 General Description ......................................................................... 1 Applications..................................................................................... 14 Revision History ............................................................................... 2 Input and Output Matching...................................................... 14 Specifications..................................................................................... 3 VGA Operation .......................................................................... 15 Absolute Maximum Ratings............................................................ 5 Modulated Gain Mode .............................................................. 15 ESD Caution.................................................................................. 5 AGC Operation .......................................................................... 15 Pin Configuration and Function Descriptions............................. 6 Modifying the AGC Setpoint.................................................... 16 Typical Performance Characteristics ............................................. 7 Evaluation Board........................................................................ 19 Theory of Operation ...................................................................... 11 Characterization Setup and Methods ...................................... 20 Input Attenuator and Gain Control ......................................... 11 Outline Dimensions ....................................................................... 21 Input and Output Interfaces...................................................... 11 Ordering Guide .......................................................................... 21 Power and Voltage Metrics........................................................ 12 REVISION HISTORY 7/05Rev. 0 to Rev. A Changes to Format .............................................................Universal Changes to General Description .................................................... 1 Changes to Table 1............................................................................ 3 Changes to Table 3............................................................................ 6 Changes to Figure 8.......................................................................... 7 Changes to Figure 9, Figure 12, and Figure 14 ............................. 8 Changes to Input and Output Interfaces Section ....................... 11 Changes to Output Centering Section and Figure 31................ 12 Changes to RMS Detection Section ............................................. 13 Changes to Figure 32, Table 4, and Table 5 ................................. 14 Changes to Figure 33, Figure 34, and AGC Operation Section................................................................. 15 Changes to the Modifying the AGC Set Point Section.............. 16 Changes to Figure 38...................................................................... 17 Changes to Figure 42...................................................................... 19 Changes to Table 7.......................................................................... 20 Moved Table 7 to Page ................................................................... 20 Moved Characterization Setup and Methods Section to Page . 20 Moved Figure 45 to Page ............................................................... 20 Changes to Ordering Guide .......................................................... 21 Updated Outline Dimensions ....................................................... 21 10/01Revision 0: Initial Version Rev. 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