AFE1302 Datasheet, PDF (1/13 Pages) Texas Instruments – ADSL ANALOG FRONT-END

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AFE1302
AFE1302
ADSL ANALOG FRONT-END
FEATURES
q NOISE FLOOR: –144dBm/Hz
q MULTIRATE COMPATIBLE
q VCXO CIRCUITRY AND DAC
q 8.8M TO 1.1MWords/s WORD RATE
q FIVE GENERAL-PURPOSE OUTPUTS
q 570mW POWER DISSIPATION
q TQFP-48 PACKAGE
DESCRIPTION
Burr-Brown’s Analog Front-End from Texas Instru-
ments reduces the size and cost of an ADSL-compliant
system by providing the active analog circuitry needed
to connect an ADSL Digital Signal Processor (DSP) to
an external line driver, receiver, TX/RX filters, hy-
brid, transformer, and POTS filter. The AFE1302 is
designed for downstream data rates of 4Mbps and
higher, and operation at a clock rate of 35.328MHz,
with an output word rate of up to 8.832MWords/s.
Functionally, this unit consists of a transmit (TX) chan-
nel, a receive (RX) channel, a VCXO (Voltage Con-
trolled Crystal Oscillator) control Digital-to-Analog
Converter (DAC), and VCXO active circuitry. The TX
section converts, filters, and buffers outgoing Discrete
Multi Tone (DMT) data from the ADSL DSP.
The receive section amplifies, filters, and digitizes the
DMT data received on the twisted pair line.
This IC operates on a single 5V supply. The digital
circuitry in the unit can be connected to a supply voltage
ranging from 3.3V to 5V. The chip uses only 570mW.
The AFE1302 is designed to be used with external
amplifiers and filters for noise reduction and dynamic-
range improvement.
The RX channel consists of a low-noise PGA, a switched
capacitor low-pass filter, and fourth-order delta-sigma
Analog-to-Digital Converter (ADC). The delta-sigma
modulator operating at a 32X oversampling ratio pro-
duces a 16-bit output at word rates up to 8832kHz.
The TX channel consists of a fourth-order delta-sigma
DAC, switched-capacitor low-pass filter, program-
mable attenuator, and buffer. The buffer drives off-
chip into a low-noise line driver configured as a 3-pole
active filter to produce an overall low-noise high-drive
TX output signal on a twisted pair line.
Patents Pending
AFE1302
Interpolation
Filter
Digital
Loopback
Decimation
Filter
16-Bit
DAC
16-Bit
ADC
LP
Filter
Atten
Buffer
TX Output
LP
Filter
PGA
Analog
Loop Back
RX Input
From DSP
Digital
Interface
VCXO
DAC
VCXO
Active Ckts
General Purpose ⁵
Digital Output
Copyright © 2000, Texas Instruments Incorporated
SBWS014
Printed in U.S.A. December, 2000