AD9875 Datasheet, PDF (1/24 Pages) Analog Devices – Broadband Modem Mixed-Signal Front End

a
Broadband Modem
Mixed-Signal Front End
AD9875
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
FUNCTIONAL BLOCK DIAGRAM
PWR DN
AD9875
Tx QUIET
GAIN
Tx [5:0]
Tx SYNC
Tx ¹⁰
MUX
10
Kx INTERPOLATION
LPF/BPF
TxDAC+
Tx+
Tx–
CLK-A
CLK-B
Rx SYNC
PLL-A
؋L
CLOCK GEN
PLL-B
؋ M/N
V_REF
VRC
GATE
FB
OSCIN
XTAL
Rx [5:0]
Rx
MUX ₁₀
ADC
PGA
Rx+
LPF
PGA
Rx–
SPORT ³
REGISTER
CONTROL
PRODUCT DESCRIPTION
The AD9875 is a single supply Broadband modem mixed-
signal front end (MxFE) IC. The devices contain a transmit
path Interpolation Filter and DAC, and a receive path PGA,
LPF 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.
The AD9875 provides 10-bit converter performance on both
the Tx and Rx paths.
The TxDAC+ 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.
The transmit path signal bandwidth can be as high as 26 MHz
at an input data rate of 64 MSPS. The 10-bit DAC provides
differential current outputs for optimum noise and distortion
performance. The DAC full-scale current can be adjusted
from 2 mA to 20 mA by a single resistor, providing 20 dB of
additional gain range.
The receive path consists of a PGA, LPF, and ADC. The 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.
The receive path LPF cutoff frequency can be programmed to either
12 MHz or 26 MHz. The filter cutoff frequency can also be tuned
or bypassed where filter requirements differ. The 10-bit ADC uses
a multistage differential pipeline architecture to achieve excellent
dynamic performance with low power consumption.
The 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.
The 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.
The 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.
The AD9875 is pin-compatible with the 12-bit AD9876. Both are
available in a space-saving 48-lead LQFP package. They are speci-
fied over the industrial (–40°C to +85°C) temperature range.
MxFE is a trademark of Analog Devices, Inc.
TxDAC+ is a registered trademark of Analog Devices, Inc.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
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© Analog Devices, Inc., 2001