REV. A

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A

AD9876

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

www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 2002

a

2

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

12

12

12

AD9876

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 AD9876 is a single-supply broadband modem mixed-signal

front end (MxFE) IC. The device contains 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 provides all required

clocks from a single crystal or clock input. The AD9876 provides

12-bit converter performance on both the Tx and Rx path.

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 12-bit DAC provides

differential current outputs for optimum noise and distortion

performance. The DAC full-scale current can be adjusted from

2 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 PGA has

a gain range of –6 dB to +36 dB, programmable in 2 dB steps,

adding 42 dB of dynamic range to the receive path. The receive

MxFE is a trademark of Analog Devices, Inc.

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

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 12-bit ADC uses

a multistage differential pipeline architecture to achieve excellent

dynamic performance with low power consumption.

The AD9876 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 six bits and are clocked at a frequency of twice the

12-bit word rate.

The AD9876 ADC and/or DAC can also be used at sampling

rates as high as 64 MSPS in a 6-bit resolution nonmulti-

plexed mode.

The AD9876 is pin compatible with the 10-bit AD9875. 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