DESCRIPTION

The AD8320 is a digitally controlled variable gain amplifier optimized for coaxial line driving applications. An 8-bit serial word determines the desired output gain over a 36 dB range (256 gain levels). The AD8320 provides linear gain response.

The AD8320 is made up of a digitally controlled variable at tenuator of 0 dB to –36 dB, which is preceded by a low noise, fixed gain buffer and followed by a low distortion high power amplifier. The AD8320 has a 220 Ω input impedance and accepts a single-ended input signal with a specified analog input level of up to 0.310 V p-p. The output is specified for driving a 75 Ω load, such as coaxial cable, although the AD8320 is capable of driving other loads. Distortion performance of –57 dBc is achieved with an output level up to 12 dBm (3.1 V p-p) at 42 MHz, while –46 dBc distortion is achieved with an output level up to 18 dBm (6.2 V p-p).

FEATURES

  8-Bit Serial Gain Control

     V/V/LSB Linear Gain Response

  36 dB Gain Range

     ±0.20 dB Gain Accuracy

  Upper Bandwidth: 150 MHz

  22 dBm 1 dB Compression Point (75 V)

  Drives Low Distortion Signals into 75 V Load:

     –57 dBc SFDR at 42 MHz and 12 dBm Out

     –46 dBc SFDR at 42 MHz and 18 dBm Out

  Single Supply Operation from 5 V to 12 V

  Maintains 75 V Output Impedance Power-Up and Power-Down Condition

  Supports SPI Input Control Standard

APPLICATIONS

  Coaxial Cable Driver

     HFC Cable Telephony Systems

     HFC High Speed Data Modems

     Interactive Set-Top Boxes

     PC Plug-In Modems

  Interfaces with AD9853 I2C Controlled Digital Modulator

  High Performance Digitally Controlled Variable Gain Block