AD9867: Broadband Modem Mixed-Signal Front End

The AD9867 is a mixed-signal front-end (MxFE) IC for transceiver applications requiring Tx and Rx path functionality with data rates up to 75 MSPS. Its flexible digital interface, power-saving modes, and high Tx-to-Rx isolation make the part well suited for half- and full-duplex applications. The digital interface is extremely flexible allowing simple interfaces to digital back ends. Power-saving modes can reduce power consumption of individual functional blocks or can power down unused blocks in half-duplex applications. A serial port interface (SPI®) allows software programming of the various functional blocks. An on-chip PLL clock multiplier and synthesizer provide all the required internal clocks, as well as two external clocks from a single crystal or clock source.

The Tx signal path consists of a bypassable 2/4 low-pass interpolation filter and a 10-bit, 250 MSPS TxDAC. The transmit path signal bandwidth can be as high as 33.6 MHz at an input data rate of 75 MSPS. The TxDAC provides differential current outputs that can be steered directly to a differential or single-ended external load. Tx power can be digitally controlled over a 7.5 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 less than 3.6 nV/rtHz for gain settings beyond 36 dB. An optional attenuator provides an additional 6 dB (or more) of attenuation (when combined with external series resistors). The receive path LPF cutoff frequency can either be set over a 22 MHz to 38 MHz range or simply bypassed. The 10-bit ADC achieves excellent dynamic performance over a 5 MSPS to 75 MSPS span. Both the RxPGA and the ADC offer scalable power consumption allowing power/performance optimization.

The AD9867 provides a highly integrated solution for broadband modems. It is available in a space-saving, 64-lead chip scale package and is specified over the commercial (40°C to +85°C) temperature range.

Applications

• Power-line networking

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