Broadband Modem Mixed-Signal Front End
Low cost 3.3 V CMOS MxFE for broadband modems
12-bit DAC converter
2×/4× interpolation filter
200 MSPS DAC update rate
Integrated 17 dBm line driver with 19.5 dB gain control
12-bit, 80 MSPS, ADC converter
−12 dB to +48 dB low noise RxPGA (<3 nV/√Hz)
Third-order, programmable low-pass filter
Flexible digital data path interface
Half- and full-duplex operation
Pin compatible with the AD9866
Various power-down/reduction modes
Internal clock multiplier (PLL)
2 auxiliary programmable clock outputs
Available in a 64-lead LFCSP_VQ
Broadband wireline networking
The AD9869 is a mixed-signal front-end (MxFE®) IC for
transceiver applications requiring Tx path and Rx path
functionality with data rates up to 80 MSPS. A lower cost, pin-
compatible version of the AD9866, the AD9869 removes the
current amplifier (IAMP) IOUTP functionality and limits the
PLL VCO operating range of 80 MHz to 200 MHz.
The part is well suited for half- and full-duplex applications.
The digital interface is extremely flexible, allowing simple
interfacing to digital back ends that support half- or full-duplex
data transfers, often allowing the AD9869 to replace discrete
ADC and DAC solutions. Power-saving modes include the
ability to reduce power consumption of individual functional
blocks or 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 2×/4× low-pass interpolation
filter, a 12-bit TxDAC, and a line driver. The transmit path
signal bandwidth can be as high as 34 MHz at an input data rate
FUNCTIONAL BLOCK DIAGRAM
0 TO –7.5dB 0 TO –12dB
0 TO 6dB –6 TO +18dB –6 TO +24dB
4 REGISTER ∆ = 1dB ∆ = 6dB
∆ = 6dB
of 80 MSPS. The TxDAC provides differential current outputs
that can be steered directly to an external load or to an internal
low distortion current amplifier (IAMP) capable of delivering
17 dBm peak signal power. Tx power can be 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 12-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 nV/√Hz for gain
settings beyond 36 dB. The receive path LPF cutoff frequency
can be set over a 15 MHz to 35 MHz range or it can be simply
bypassed. The 12-bit ADC achieves excellent dynamic performance
up to an 80 MSPS span. Both the RxPGA and the ADC offer
scalable power consumption allowing power/performance
The AD9869 provides a highly integrated solution for many
broadband modems. It is available in a space-saving package, a
16-lead LFCSP, and is specified over the commercial temperature
range (−40°C to +85°C).
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