LF to 750 MHz, Digitally Controlled VGA Data Sheet AD8370 FEATURES FUNCTIONAL BLOCK DIAGRAM Programmable low and high gain (<2 dB resolution) VCCI VCCO VCCO 3 11 6 Low range: 11 dB to +17 dB High range: 6 dB to 34 dB 4 PWUP BIAS CELL 5 VOCM Differential input and output ICOM 2 7 OCOM 200 differential input 100 differential output 1 8 INHI OPHI PRE OUTPUT TRANSCONDUCTANCE 7 dB noise figure maximum gain AMP AMP 16 9 INLO OPLO Two-tone IP3 of 35 dBm 70 MHz 3 dB bandwidth of 750 MHz ICOM 15 10 OCOM SHIFT REGISTER 40 dB precision gain range AND LATCHES Serial 8-bit digital interface AD8370 Wide input dynamic range 14 13 12 DATA CLCK LTCH Power-down feature Single 3 V to 5 V supply Figure 1. 70 40 CODE = LAST 7 BITS OF GAIN CODE APPLICATIONS (NO MSB) 60 30 Differential ADC drivers HIGH GAIN MODE IF sampling receivers 50 20 RF/IF gain stages LOW GAIN MODE Cable and video applications 40 10 GAIN 0.409 SAW filter interfacing CODE HIGH GAIN MODE 30 0 Single-ended-to-differential conversion 20 10 GENERAL DESCRIPTION GAIN 0.059 10 20 CODE The AD8370 is a low cost, digitally controlled, variable gain LOW GAIN MODE amplifier (VGA) that provides precision gain control, high IP3, 0 30 0 1020 3040 50 60 70 80 90 100 110 120 130 and low noise figure. The excellent distortion performance and GAIN CODE wide bandwidth make the AD8370 a suitable gain control Figure 2. Gain vs. Gain Code at 70 MHz device for modern receiver designs. For wide input, dynamic range applications, the AD8370 provides Gain control of the AD8370 is through a serial 8-bit gain control two input ranges: high gain mode and low gain mode. A vernier, word. The MSB selects between the two gain ranges, and the 7-bit, transconductance (gm) stage provides 28 dB of gain range remaining 7 bits adjust the overall gain in precise linear gain steps. at better than 2 dB resolution and 22 dB of gain range at better than Fabricated on the ADI high speed XFCB process, the high 1 dB resolution. A second gain range, 17 dB higher than the first, bandwidth of the AD8370 provides high frequency and low can be selected to provide improved noise performance. distortion. The quiescent current of the AD8370 is 78 mA The AD8370 is powered on by applying the appropriate logic typically. The AD8370 amplifier comes in a compact, thermally level to the PWUP pin. When powered down, the AD8370 enhanced 16-lead TSSOP package and operates over the consumes less than 4 mA and offers excellent input to output temperature range of 40C to +85C. isolation. The gain setting is preserved when operating in a power-down mode. 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 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 2005-2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. VOLTAGE GAIN (V/V) 03692-002 VOLTAGE GAIN (dB) 03692-001AD8370 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Basic Connections ...................................................................... 15 Applications ....................................................................................... 1 Gain Codes .................................................................................. 15 General Description ......................................................................... 1 Power-Up Feature ....................................................................... 15 Functional Block Diagram .............................................................. 1 Choosing Between Gain Ranges .............................................. 16 Revision History ............................................................................... 2 Layout and Operating Considerations .................................... 16 Specifications ..................................................................................... 3 Package Considerations ............................................................. 17 Absolute Maximum Ratings ............................................................ 5 Single-Ended-to-Differential Conversion ............................... 17 ESD Caution .................................................................................. 5 DC-Coupled Operation............................................................. 18 Pin Configuration and Function Descriptions ............................. 6 ADC Interfacing ......................................................................... 19 Typical Performance Characteristics ............................................. 7 3 V Operation ............................................................................. 20 Theory of Operation ...................................................................... 13 Evaluation Board and Software .................................................... 22 Block Architecture ...................................................................... 13 Appendix ......................................................................................... 25 Preamplifier ................................................................................. 13 Characterization Equipment..................................................... 25 Transconductance Stage ............................................................ 13 Composite Waveform Assumption .......................................... 25 Output Amplifier ........................................................................ 14 Definitions of Selected Parameters .......................................... 25 Digital Interface and Timing .................................................... 14 Outline Dimensions ....................................................................... 28 Applications ..................................................................................... 15 Ordering Guide .......................................................................... 28 REVISION HISTORY 12/11Rev. A to Rev. B Changes to Slew Rate Parameters, Table 1 .................................... 3 Updated Outline Dimensions ....................................................... 28 Changes to Ordering Guide .......................................................... 28 7/05Rev. 0 to Rev. A Changes to Features .......................................................................... 1 Changes to Table 1 ............................................................................ 3 Changes to Figure 11 and Figure 15 ............................................... 8 Added Figure 12 Renumbered Sequentially ................................ 8 Added Figure 16 Renumbered Sequentially ................................ 9 Changes to Evaluation Board and Software Section .................. 22 Changes to Figure 60 ...................................................................... 23 Updated Outline Dimensions ....................................................... 28 Changes to Ordering Guide .......................................................... 28 1/04Revision 0: Initial Version Rev. B Page 2 of 28