GENERAL DESCRIPTION
The AD8323 is a low-cost, digitally controlled, variable gain amplifier optimized for coaxial line driving applications such as cable modems that are designed to the MCNS-DOCSIS upstream standard. An 8-bit serial word determines the desired output gain over a 53.5 dB range resulting in gain changes of 0.7526 dB/LSB. The AD8323 comprises a digitally controlled variable attenuator of 0 dB to –53.5 dB, which is preceded by a low noise, fixed gain buffer and is followed by a low distortion high power am plifier. The AD8323 accepts a differential or single-ended input signal. The output is specified for driving a 75 Ω load, such as coaxial cable.

FEATURES
Supports DOCSIS Standard for Reverse Path Transmission
Gain Programmable in 0.75 dB Steps Over a 53.5 dB Range
Low Distortion at 60 dBmV Output
  –56 dBc SFDR at 21 MHz
  –55 dBc SFDR at 42 MHz
Output Noise Level
  –48 dBmV in 160 kHz
Maintains 75
Output Impedance Power-Up and Power-Down Condition
Upper Bandwidth: 100 MHz (Full Gain Range)
5 V Supply Operation
Supports SPI Interfaces

APPLICATIONS
Gain-Programmable Line Driver
HFC High-Speed Data Modems
Interactive Set-Top Boxes
PC Plug-in Modems
General-Purpose Digitally Controlled Variable Gain Block

ABSOLUTE MAXIMUM RATINGS*
Supply Voltage +VS
Pins 5, 9, 10, 19, 20, 23, 27 . . . . . . . . . . . . . . . . . . . . . . 6 V
Input Voltages
   Pins 25, 26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±0.5 V
   Pins 1, 2, 3, 6, 7 . . . . . . . . . . . . . . . . . . . . . –0.8 V to +5.5 V
Internal Power Dissipation
   TSSOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.9 W
Operating Temperature Range . . . . . . . . . . . –40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Lead Temperature, Soldering 60 seconds . . . . . . . . . . . 300°C