REV. 0

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AD9875

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781/329-4700

www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 2001

a

Broadband Modem

Mixed-Signal Front End

FUNCTIONAL 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

CLOCK GEN

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.

MxFE is a trademark of Analog Devices, Inc.

TxDAC+ is a registered trademark of Analog Devices, Inc.

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.

FEATURES

Low Cost 3.3 V-CMOS Mixed-Signal Front End (MxFE™)

Converter for Broadband Modems

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