Description

The AD9865 is a mixed-signal front end (MxFE) IC fortransceiver applications requiring Tx and Rx path functionalitywith data rates up to 80 MSPS. Its flexible digital interface,power saving modes, and high Tx-to-Rx isolation make it wellsuited for half- and full-duplex applications. The digital interfaceis extremely flexible allowing simple interfaces to digitalback ends that support half- or full-duplex data transfers, thusoften allowing the AD9865 to replace discrete ADC and DACsolutions. Power saving modes include the ability to reducepower consumption of individual functional blocks, or to powerdown unused blocks in half-duplex applications. A serial portinterface (SPI®) allows software programming of the variousfunctional blocks. An on-chip PLL clock multiplier andsynthesizer provide all the required internal clocks, as well astwo external clocks from a single crystal or clock source.The Tx signal path consists of a bypassable 2×/4× low-passinterpolation filter, a 10-bit TxDAC, and a line driver. Thetransmit path signal bandwidth can be as high as 34 MHz at aninput data rate of 80 MSPS. The TxDAC provides differentialcurrent outputs that can be steered directly to an external loador to an internal low distortion current amplifier. The currentamplifier (IAMP) can be configured as a current- or voltage-modeline driver (with two external npn transistors) capable ofdelivering in excess of 23 dBm peak signal power. Tx power canbe digitally controlled over a 19.5 dB range in 0.5 dB steps.The receive path consists of a programmable amplifier(RxPGA), a tunable low-pass filter (LPF), and a 10-bit ADC.The low noise RxPGA has a programmable gain range of−12 dB to +48 dB in 1 dB steps. Its input referred noise is lessthan 3 nV/rtHz for gain settings beyond 36 dB. The receive pathLPF cutoff frequency can be set over a 15 MHz to 35 MHzrange or simply bypassed. The 10-bit ADC achieves excellentdynamic performance over a 5 MSPS to 80 MSPS span. Boththe RxPGA and the ADC offer scalable power consumptionallowing power/performance optimization.The AD9865 provides a highly integrated solution for manybroadband modems. It is available in a space saving 64-pin chipscale package and is specified over the commercial (−40°C to+85°C) temperature range.Applications Powerline networking VDSL and HPNA