The
Communications
Company
TM
O V E R V I E W
Asymmetric digital subscriber line (ADSL) technology provides a viable solution
to meet the emerging need for high-bandwidth communications to the home while
utilizing existing twisted-pair copper infrastructure. LSI Logic's SpeedREACH
analog front ends (AFEs) meet this need by boosting the performance of customer
premise and central office equipment, creating new market opportunities for
OEMs. To simplify the design and reduce deployment costs, LSI Logic has
developed SpeedREACH AR8101, which is designed to perform all of the analog
functions of the receive (RX) and transmit (TX) paths, both full-rate and G.lite, for
customer premise modems. By integrating the line driver, AR8101 represents a
significant cost reduction for ADSL modem manufacturers, while maintaining the
excellent linearity performance of the DPS8001. The chip requires no external
circuitry beyond a pair of precision resistors and bypass/coupling capacitors.
The RX portion of the chip consists of a low-noise programmable gain
amplifier (PGA) having a gain range of -6 dB to +38 dB in 0.25 dB steps, an
anti-aliasing filter, and a 16-bit analog-to-digital converter (ADC). The TX portion
consists of a 16-bit digital-to-analog converter (DAC), a transmit low-pass filter,
and a programmable attenuation amplifier (PAA) with an attenuation of 0 dB to
-24 dB. To simplify the overall system design, DAC droop compensation is
handled internally, removing this burden from the back-end signal processing.
SpeedREACH
TM
AR8101 -- ADSL
AFE for CPE with +5 V Line Driver
F E A T U R E S
ADSL CPE AFE with full RX and TX
analog signal path including integrated
upstream TX line driver
Fully monolithic: only 2 precision
resistors, 2 non-critical resistors, and
decoupling capacitors required
Compatible with both ITU G.992.1
(G.dmt) and G.992.2 (G.lite) standards
Integrated line driver capable of
driving +13 dBM onto the line using a
4.25:1 transformer
Power: 1W (driving +13 dBm DMT
signal onto the line)
Line driver total harmonic distortion for
138 kHz sinewave at 7.4 V peak-to-
peak differential with either (a) 11
W
resistance load or (b) 5.5
W resistance
and 4.25:1 transformer: -85 dB
14-bit linear 4.4 MS/s ADCs and
14-bit linear 4.4 MS/s DACs
Entire RX channel linearity: 80 dB MTPR
Entire TX channel linearity: 80 dB MTPR
RX path noise floor: -160 dBm/Hz
12-bit DAC to support external VCXO
4th-order low-pass filters for RX/TX paths,
with 5% cutoff frequency accuracy
TX channel: support for 138 kHz and
276 kHz (for ADSL over ISDN)
RX channel: support for both 552 kHz
(G.lite) and 1.104 MHz (G.dmt)
DAC
4.4MHz
16
TX LPF
138kHz/
276kHz
DAC
4.4MHz
TX Out
16
PAA and Line Driver
TX LPF
138kHz/
276kHz
Support Blocks
VCXO DAC
G.hs wakeup detector
D
I
G
I
T
A
L
I/F
4
TX
4
EC
MCLK
35.328 MHz
Echo Out
PAA
ADC
4.4MS/s /
2.2 MS/s
RX In
16
Fine PGA
Low-Noise Coarse PGA
RX LPF
1.1MHz/
552kHz
4
RX
Figure 1. Block diagram of the SpeedREACH AR8101.
The
Communications
Company
TM
SpeedREACH
TM
AR8101
This device includes an integrated TX line driver and, with an appropriate
4.25:1 step up transformer, can drive +13 dBm onto the twisted pair line, as
required for the upstream channel in both G.992.1 and G.992.2. Integrating the
+5 V line driver eliminates the need for a +12 V supply which is required to
power an external line driver. Total harmonic distortion of the entire TX channel
including line driver is better than -80 dB at full power (+13 dBm on the line).
Apart from the primary signal paths, the chip also contains support circuitry
for other functions required in an ADSL modem. To assist in timing recovery, a
12-bit DAC is present to drive an off-chip voltage controlled crystal oscillator
(VCXO).
A 4-wire serial port provides a simple DSP interface. The serial port is used
to modify internal register values, which in turn control attenuation/gain settings,
filter bandwidths and the power down of individual blocks. The chip is powered
off a +5 V supply while all digital I/Os run off a +3.3 V supply. The AR8101 is
available in a 80-pin LQFP plastic package. The operating temperature range
is between -40 C and +85 C.
For more information please call:
LSI Logic Corporation
North American Headquarters
Milpitas, CA
Tel: 800 574 4286
LSI Logic Europe Ltd.
European Headquarters
United Kingdom
Tel: 44 1344 426544
Fax: 44 1344 481039
LSI Logic KK Headquarters
Tokyo, Japan
Tel: 81 3 5463 7165
Fax 81 3 5463 7820
LSI Logic web site
www.lsilogic.com
LSI Logic logo design, is a registered trademark
and SpeedREACH is a trademark of LSI Logic
Corporation. All other brand and product names
may be trademarks of their respective companies.
LSI Logic Corporation reserves the right to make
changes to any products and services herein at any
time without notice. LSI Logic does not assume any
responsibility or liability arising out of the
application or use of any product or service
described herein, except as expressly agreed to in
writing by LSI Logic; nor does the purchase, lease,
or use of a product or service from LSI Logic
convey a license under any patent rights,
copyrights, trademark rights, or any other of the
intellectual property rights of LSI Logic or of third
parties.
Copyright 2001 by LSI Logic Corporation.
All rights reserved.
Order No. R200026
101.1k.JG.TP - Printed in USA
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