
REV. 0
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AD9875
Tel: 781/329-4700Fax: 781/326-8703
Analog Devices, Inc., 2001a
Broadband Modem
Mxed-Signal Front End
FUNCT IONAL BLOCK DIAGRAM
REGISTER
CONTROL
Rx
MUX
ADC
PGA
LPF
PGA
TxDAC+
Kx INTERPOLATION
LPF/BPF
Tx
MUX
PLL-A
L
PLL-B
M/N
VRC
3
10
10
10
AD9875
Tx+
Tx–
GATE
FB
OSCIN
XTAL
Rx+
Rx–
PWR DN
Tx QUIET
GAIN
Tx [5:0]
Tx SYNC
CLK-A
CLK-B
Rx SYNC
Rx [5:0]
SPORT
V
REF
CLOCK GEN
PRODUCT DE SCRIPT ION
T he AD9875 is a single supply Broadband modem mixed-
signal front end (MxFE) IC. T he devices contain a transmit
path Interpolation Filter and DAC, and a receive path PGA,
L PF and ADC supporting a variety of Broadband modem
applications. Also on-chip is a PLL clock multiplier that pro-
vides all required clocks from a single crystal or clock input.
T he AD9875 provides 10-bit converter performance on both
the T x and Rx paths.
T he T xDAC+ uses a selectable digital 2
×
or 4
×
interpolation
low-pass or band-pass filter to further oversample transmit
data and reduce the complexity of analog reconstruction filtering.
T he transmit path signal bandwidth can be as high as 26 MHz
at an input data rate of 64 MSPS. T he 10-bit DAC provides
differential current outputs for optimum noise and distortion
performance. T he DAC full-scale current can be adjusted
from 2 mA to 20 mA by a single resistor, providing 20 dB of
additional gain range.
T he receive path consists of a PGA, LPF, and ADC. T he two-stage
PGA has a gain range of –6 dB to +36 dB, and is programmable
in 2 dB steps, adding 42 dB of dynamic range to the receive path.
MxFE is a trademark of Analog Devices, Inc.
T xDAC+ is a registered trademark of Analog Devices, Inc.
T he receive path LPF cutoff frequency can be programmed to either
12 MHz or 26 MHz. T he filter cutoff frequency can also be tuned
or bypassed where filter requirements differ. T he 10-bit ADC uses
a multistage differential pipeline architecture to achieve excellent
dynamic performance with low power consumption.
T he AD9875 provides a voltage regulator controller (VRC) that
can be used with an external power MOSFET transistor to form
a cost-effective 1.3 V linear regulator.
T he digital transmit and receive ports are each multiplexed to a
bus width of 5/6 bits and are clocked at a frequency of twice the
10-bit word rate.
T he AD9875 ADC and/or DAC can also be used at higher
sampling rates as high as 64 MSPS in a 5-bit resolution non-
multiplexed mode.
T he AD9875 is pin-compatible with the 12-bit AD9876. Both are
available in a space-saving 48-lead LQFP package. T hey are speci-
fied over the industrial (–40
°
C to +85
°
C) temperature range.
FEATURES
Low Cost 3.3 V-CMOS Mixed-Signal Front End (
MxFE
)
Converter for Broadband Modems
10-/12-Bit D/A Converter (TxDAC+
)
64/32 MSPS Input Word Rate
2 /4 Interpolating LPF or BPF Transmit Filter
128 MSPS DAC Output Update Rate
Wide (26 MHz) Transmit Bandwidth
Power-Down Mode
10-/12-Bit, 50 MSPS A/D Converter
Fourth Order Low-Pass Filter 12 MHz or 26 MHz
with Bypass
–6 dB to +36 dB Programmable Gain Amplifier
Internal Clock Multiplier (PLL)
Clock Outputs
Voltage Regulator Controller
48-Lead LQFP Package
APPLICATIONS
Powerline Networking
Home Phone Networking
xDSL
Broadband Wireless
Home RF