The AD9868 is a functional application IC for mixed-signal front-end (MxFE ®) transceivers requiring Tx channels and receive paths with data rates up to 80 MSPS.At a lower cost, pin-compatible version of the AD9865, the AD9868 removes the current amplifier (IAMP) IOUTP function, limiting the PLL VCO operating range to 80 MHz to 200 MHz.
The device is also ideal for half- and full-duplex applications.The digital interface is very flexible, allowing the back end of a simple digital interface to support half-duplex or full-duplex data transmission, often making the AD9868 an alternative to discrete ADC and DAC solutions.Power-down modes include the ability to reduce power consumption on unused blocks for individual functional blocks or falling half-duplex applications.A serial interface (SPI) enables the programming of various functional blocks of the software.The on-chip PLL clock multiplier and synthesizer provide all the necessary internal clocks, as well as two clocks from a single crystal or external clock source.
The TX signal path consists of a 2x/4x low-pass filter, a 10-bit TxDAC, and line drivers.The transmission bandwidth of the path signal can be up to 34 MHz at an 80 MSPS input data rate.The TxDAC family provides a differential peak signal that leads directly to an external load or an internal low distortion current amplifier current output (IAMP) to deliver 17 dBm of power.The transmit power can be digitally controlled in 0.5 dB steps in the 19.5 dB range.
The receive path consists of a programmable amplifier (RxPGA), an adjustable low-pass filter (LPF), and a 10-bit ADC.The low-noise RxPGA has -12 dB programmable to +48 dB gain in a 1 dB range.Its input-referenced noise is less than 3 nanovolts after the gain is set to 36 dB/√Hz.The low-pass filter cutoff frequency can be set to the receive channel from 15 MHz to 35 MHz or simply bypassed.The 10-bit ADC achieves superior power performance over a span of 80 MSPS.Both RxPGA and ADC offer scalability, allowing for power consumption/performance optimization.
The AD9868 provides a highly integrated solution for many broadband modems.It is available in a space-saving package, 16-pin LFCSP package, and is available in the commercial temperature range (-40°C to +85°C).
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