Triple Differential Receiver with Adjustable Line Equalization:AD8123

The AD8123 is a triple high speed, differential receiver/equalizer that compensates for the transmission losses of unshielded twisted pair (UTP) and coaxial cables up to 300 meters. Various gain stages are summed together to best approximate the inverse frequency response of the cable. Logic circuitry inside the AD8123 controls the gain functions of the individual stages so that the lowest noise can be achieved at short to medium cable lengths. This technique optimizes its performance for low noise and for short to medium range applications, while at the same time providing the high gain bandwidth required for long cable equalization (up to 300m). Each channel features a high impedance differential input that is ideal for interfacing directly to the cable.

The AD8123 has three control pins for optimal cable compensation, as well as an output offset adjust pin. Two voltage controlled pins are used to compensate for different cable lengths; the V_PEAK pin controls the amount of high frequency peaking, and the V_GAIN pin adjusts the broadband flat gain, which compensates for the low frequency flat cable loss. For added flexibility, an optional pole adjustment pin, V_POLE, allows movement of the pole locations, allowing for the compensation of different gauges and types of cable as well as variations between different cables and/or equalizers. The V_OFFSET pin allows the dc voltage at the output to be shifted by up to ¡À2.5 V, adding flexibility for dc-coupled systems.

The AD8123 is available in a 6 mm 6 mm 40-lead LFCSP package and is rated to operate over the extended temperature range of -40¡ãC to +85¡ãC.