Untitled Document
LXT400
All Rate Extended Range Switched 56/DDS Transceiver
Datasheet
General Description
The LXT400 is an integrated line interface circuit for Switched 56 (SW 56) and Digital Data
Service (DDS), compatible with any combination of 19 to 26 AWG cable. The LXT400
operates at any of 17 preset data rates from 2.4 kbps to 72.0 kbps, providing appropriate transmit
pulse shaping, receive signal detection and timing recovery at the metallic interface between the
carrier and the customer installation. The LXT400 offers a variety of diagnostic features
including loopback, line status and equalizer monitor outputs, while conforming to AT&T, ANSI
and Bellcore specifications.
The LXT400 transmit section includes switched capacitor filters, continuous reconstruction
filters, and a 50% AMI encoder. The AMI pulse is synchronized with the transmit clock.
The LXT400 receive section performs line equalization, data extraction and timing recovery.
The LXT400 has a BER of less than 10
-7
with up to 49 dB of cable attenuation at the Nyquist
frequency for 56, 64 and 72 kbps, and 40 dB at the lower rates. The LXT400 is an advanced
CMOS device which requires only a single +5 V power supply.
Product Features
s
Enhancements:
-- Three new data rates: 38.4, 51.2, and
64.0 kbps
-- Improved accuracy in line attenuation
reporting
-- Simplified transmit digital timing
s
Integrated transmitter, receiver and timing
recovery on a single CMOS chip
s
Transparent to framing and coding
s
Receive equalizer filters allow data
recovery from signals with up to 40 dB of
attenuation at the Nyquist frequency at line
rates below 56 kbps, and up to 49 dB at the
56, 64 and 72 kbps line rates
s
Single 4.096 MHz crystal or master clock
input
s
Digital back-end loopback (CSU
Loopback)
s
Equalizer output monitor pin
s
Line status (loop length, RLOS, etc.)
information available for maintenance
purposes
s
Low power consumption (200 mW typical)
s
Available in 28-pin plastic DIP and PLCC
s
Single 5 V only CMOS technology
As of January 15, 2001, this document replaces the Level One document
Order Number: 249027-001
LXT400 -- All Rate Extended Range Switched 56/DDS Transceiver.
January 2001
Datasheet
Information in this document is provided in connection with Intel
products. No license, express or implied, by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Intel's Terms and Conditions of Sale for such products, Intel assumes no liability
whatsoever, and Intel disclaims any express or implied warranty, relating to sale and/or use of Intel products including liability or warranties relating to
fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. Intel products are not
intended for use in medical, life saving, or life sustaining applications.
Intel may make changes to specifications and product descriptions at any time, without notice.
Designers must not rely on the absence or characteristics of any features or instructions marked "reserved" or "undefined." Intel reserves these for
future definition and shall have no responsibility whatsoever for conflicts or incompatibilities arising from future changes to them.
The LXT400 may contain design defects or errors known as errata which may cause the product to deviate from published specifications. Current
characterized errata are available on request.
Contact your local Intel sales office or your distributor to obtain the latest specifications and before placing your product order.
Copies of documents which have an ordering number and are referenced in this document, or other Intel literature may be obtained by calling 1-800-
548-4725 or by visiting Intel's website at http://www.intel.com.
Copyright Intel Corporation, 2001
*Third-party brands and names are the property of their respective owners.
Datasheet
3
All Rate Extended Range Switched 56/DDS Transceiver -- LXT400
Contents
1.0
Pin Assignments And Signal Descriptions ......................................................................... 8
2.0
Functional Description...................................................................................................... 10
2.1
Introduction.......................................................................................................... 10
2.2
Initialization.......................................................................................................... 10
2.2.1
Reset ......................................................................................................10
2.3
Transmission ....................................................................................................... 12
2.4
Reception ............................................................................................................13
2.4.1
Changes in Received Signal Strength.................................................... 13
2.4.2
Receive Loss of Signal........................................................................... 14
2.4.3
Timing Recovery .................................................................................... 16
2.4.4
Data Extraction ....................................................................................... 16
2.5
Loopback Operation ............................................................................................ 16
2.6
Serial Port Operation........................................................................................... 16
3.0
Application Information..................................................................................................... 19
3.1
Introduction.......................................................................................................... 19
3.2
Crosstalk ............................................................................................................. 19
3.3
PCB Layout ......................................................................................................... 20
4.0
Test Specifications ........................................................................................................... 23
5.0
Mechanical Specifications ................................................................................................ 27
Figures
1
LXT400 Block Diagram ......................................................................................... 7
2
LXT400 Pin Assignments ...................................................................................... 8
3
C-Message Weighting .........................................................................................12
4
Step Changes in Received Signal Strength = 20 log10(A2/A1) dB..................... 14
5
Conditions Based on Changes in Received Signal Strength .............................. 15
6
RLOS Timing for a True Loss of Signal...............................................................15
7
RLOS Timing for a Drop in Signal Strength > 6 dB ............................................. 15
8
Typical Serial Port Output for Receive Activation @ 72 kbps ............................. 17
9
Typical Application Circuit for 72 kbps Operation................................................ 20
10
Suggested LXT400 PCB Layout ......................................................................... 21
11
Receive Digital Timing.........................................................................................25
12
Transmit Digital Timing........................................................................................ 25
13
LS Serial Port Timing - 8-Bit Word ...................................................................... 26
14
LS Serial Port Timing - 16-Bit Word .................................................................... 26
15
MCLK and RESET Timing................................................................................... 26
16
LXT400NE Package Specification ...................................................................... 27
17
LXT400PE Package Specification....................................................................... 28
LXT400 -- All Rate Extended Range Switched 56/DDS Transceiver
4
Datasheet
Tables
1
LXT400 Signal Descriptions.................................................................................. 8
2
Data Rate Programming ..................................................................................... 11
3
Ones Density Requirements ............................................................................... 11
4
Notch Filter Attenuation....................................................................................... 13
5
Frequency Limits per Data Rate ......................................................................... 14
6
LS Word Bit Assignments ................................................................................... 17
7
LS Loop Length Bits LL3 - LL0............................................................................ 18
8
External Component Recommendations ............................................................ 22
9
Absolute Maximum Ratings ................................................................................ 23
10
Recommended Operating Conditions and Characteristics ................................. 23
11
DC Electrical Characteristics (Under Recommended Operating Conditions) ..... 23
12
AC Electrical Characteristics ............................................................................... 24
13
Timing Characteristics......................................................................................... 24
Datasheet
5
All Rate Extended Range Switched 56/DDS Transceiver -- LXT400
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