AD8323

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 75Output Impedance Power-Up and Power-Down Condition Upper Bandwidth: 100 MHz (Full Gain Range) 5 V Supply Operation Supports SPI Interfaces

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

*Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

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.