AD8321AR

The AD8321AR  is a low cost digitally charged variable gain amplifier optimized for coaxial line driving applications such as cable modems that are designed to the DOCSIS* (upstream) standard. An 8-bit serial word determines the desired output gain over a 53.4 dB range, resulting in gain changes of 0.75 dB/LSB. The AD8321AR makes up a digit ally controlled variable attenuatorof 0 dB to 53.4 dB.The AD8321AR is preceded by a low noise, fixed gain buffer and followed by a low distortion high power amplifier. The AD8321AR allows a differential or single-ended input sign al. The output is specified for driving a 75 W load, such as coaxial cable, although the AD8321 can drive other loads. Performance of 53 dBc is achieved with an output level up to 11 dBm at 42 MHz bandwidth using a 9 V supply.

The AD8321AR has the following features:(1)linear in dB gain response over >53 dB range;(2)drives low distortion >11 dBm signal into 75 V Load:53 dBc SFDR at 42 MHz;(3)very Low output noise level;(4)maintains constant 75 V output impedance,power-up and power-down condition,no line transformer required;(5):upper bandwidth is 235 MHz (min gain);(6):9 V single supply operation;(7)power-down functionality;(8):supports SPI interface;low cost.

It also has some outstanding absolute maximum ratings and specifications.absolute maximum ratings:(1):supply voltage is +11 V(Pins 7, 8, 9, 17, 20);(2):input voltages is ±0.5 V(Pins 18, 19);input voltages is 0.8 V to +5.5 V(Pins 1, 2, 3, 6);(3):internal power dissipation:small outline is 0.90 W;(4):operating temperature ranges from40°C to +85°C;(5):storage temperature ranges from65°C to +150°C;(6):lead temperature at soldering 60 seconds is +300°C.specifications:(1)input characteristics:specified AC voltage is 0.137 V p-p typ when output is 11 dBm and max gain,noise figure is 15 dB typ when max gain and f is 10 MHz,input resistance is 820 of single-ended input.(2):gain conrtol interface:gain range is 52.4dB min, 53.4dB typ and 54.4 dB max,maximum gain is 25.25dB min, 26dB typ and 26.75 dB max,minimum gain is28.15dB min, 27.4dB typ and 26.4 dB max.(3)output characteristics: ban dwidth (3 dB) is 120 MHz typ of   all gain codes,bandwidth roll-off is 0.8 dB typ when f is 65 MHz;bandwidth peak ing is 0 dB when f is 65 MHz;output offset voltage is ±30 mV typ of all gain codes and full temperature range.