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AD8370 Dataheets PDF



Part Number AD8370
Manufacturers Analog Devices
Logo Analog Devices
Description Digitally Controlled VGA
Datasheet AD8370 DatasheetAD8370 Datasheet (PDF)

Data Sheet FEATURES Programmable low and high gain (<2 dB resolution) Low range: −11 dB to +17 dB High range: 6 dB to 34 dB Differential input and output 200 Ω differential input 100 Ω differential output 7 dB noise figure @ maximum gain Two-tone IP3 of 35 dBm @ 70 MHz −3 dB bandwidth of 750 MHz 40 dB precision gain range Serial 8-bit digital interface Wide input dynamic range Power-down feature Single 3 V to 5 V supply APPLICATIONS Differential ADC drivers IF sampling receivers RF/IF gain stage.

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Data Sheet FEATURES Programmable low and high gain (<2 dB resolution) Low range: −11 dB to +17 dB High range: 6 dB to 34 dB Differential input and output 200 Ω differential input 100 Ω differential output 7 dB noise figure @ maximum gain Two-tone IP3 of 35 dBm @ 70 MHz −3 dB bandwidth of 750 MHz 40 dB precision gain range Serial 8-bit digital interface Wide input dynamic range Power-down feature Single 3 V to 5 V supply APPLICATIONS Differential ADC drivers IF sampling receivers RF/IF gain stages Cable and video applications SAW filter interfacing Single-ended-to-differential conversion GENERAL DESCRIPTION The AD8370 is a low cost, digitally controlled, variable gain amplifier (VGA) that provides precision gain control, high IP3, and low noise figure. The excellent distortion performance and wide bandwidth make the AD8370 a suitable gain control device for modern receiver designs. For wide input, dynamic range applications, the AD8370 provides two input ranges: high gain mode and low gain mode. A vernier, 7-bit, transconductance (gm) stage provides 28 dB of gain range at better than 2 dB resolution and 22 dB of gain range at better than 1 dB resolution. A second gain range, 17 dB higher than the first, can be selected to provide improved noise performance. The AD8370 is powered on by applying the appropriate logic level to the PWUP pin. When powered down, the AD8370 consumes less than 4 mA and offers excellent input to output isolation. The gain setting is preserved when operating in a power-down mode. LF to 750 MHz, Digitally Controlled VGA AD8370 FUNCTIONAL BLOCK DIAGRAM VCCI 3 VCCO VCCO 11 6 PWUP 4 ICOM 2 INHI 1 INLO 16 PRE AMP BIAS CELL TRANSCONDUCTANCE OUTPUT AMP 5 VOCM 7 OCOM 8 OPHI 9 OPLO ICOM 15 SHIFT REGISTER AND LATCHES 14 13 12 DATA CLCK LTCH Figure 1. 10 OCOM AD8370 03692-001 70 CODE = LAST 7 BITS OF GAIN CODE (NO MSB) 60 HIGH GAIN MODE 50 LOW GAIN MODE 40 HIGH GAIN MODE 30 40 30 20  GAIN  0.409  CODE 10 0 VOLTAGE GAIN (dB) VOLTAGE GAIN (V/V) 03692-002 20 –10 10 LOW GAIN MODE  GAIN  0.059  CODE –20 0 –30 0 10 20 30 40 50 60 70 80 90 100 110 120 130 GAIN CODE Figure 2. Gain vs. Gain Code at 70 MHz Gain control of the AD8370 is through a serial 8-bit gain control word. The MSB selects between the two gain ranges, and the remaining 7 bits adjust the overall gain in precise linear gain steps. Fabricated on the ADI high speed XFCB process, the high bandwidth of the AD8370 provides high frequency and low distortion. The quiescent current of the AD8370 is 78 mA typically. The AD8370 amplifier comes in a compact, thermally enhanced 16-lead TSSOP package and operates over the temperature range of −40°C to +85°C. Rev. B 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 rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners. 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 © 2005-2011 Analog Devices, Inc. All rights reserved. AD8370 TABLE OF CONTENTS Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Functional Block Diagram .............................................................. 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 5 ESD Caution.................................................................................. 5 Pin Configuration and Function Descriptions............................. 6 Typical Performance Characteristics ............................................. 7 Theory of Operation ...................................................................... 13 Block Architecture...................................................................... 13 Preamplifier................................................................................. 13 Transconductance Stage ............................................................ 13 Output Amplifier........................................................................ 14 Digital Interface and Timing .................................................... 14 Applications..................................................................................... 15 REVISION HISTORY 12/11—Rev. A t.


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