AD8323

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 amplifier. The AD8323 accepts a differential or single-ended input signal. The output is specified for driving a 75 load, such as coaxial cable.

Distortion performance of 56 dBc is achieved with an output level up to 60 dBmV at 21 MHz bandwidth. A key performance and cost advantage of the AD8323 results from the ability to maintain a constant 75 output impedance during power-up and power-down conditions. This eliminates the need for external 75 termination, resulting in twice the effective output voltage when compared to a standard operational amplifier. In addition, this device has a sleep mode function that reduces the quiescent current to 4 mA.

The AD8323 is packaged in a low-cost 28-lead TSSOP, operates from a single 5 V supply, and has an operational temperature range of 40°C to +85°C.