LXT318 AN036 PE68646 PE-65839 PE65839

Transceiver Line Interface Design Guide Application Note January 2001 Order Number: 249152-001 As of January 15, 2001, this

LXT318 LXT318 Long-Haul E1 Transceiver Line Interface Design Guide Application Note January 2001 Order Number: 249152-001 As of January 15, 2001, this document replaces the Level One document known as AN036 AN036. 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 LXT318 LXT318 Long-Haul E1 Transceiver 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. Application Note LXT318 LXT318 Long-Haul E1 Transceiver Line Interface Design Guide Contents 1.0 General Description . 5 1.1 1.2 1.3 Transmit Line Interface. 5 1.1.1 Twisted-Pair Cable (120 ) . 5 1.1.2 Coaxial Cable (75 ) . 5 Circuit Modifications . 5 Receive Line Interface.6 1.3.1 Twisted-Pair Cable (120 W) . 6 1.3.2 Coaxial Cable (75 W) . 6 Figures 1 Application Note Receive Line Interface Diagram . 6 3 LXT318 LXT318 Long-Haul E1 Transceiver Line Interface Design Guide 1.0 General Description This application note describes a standard line interface for the LXT318 LXT318 transceiver in a long-haul E1 environment. The interface uses two Pulse Engineering transformers designed specifically for this transceiver. The design is simple and robust and will reduce in-house engineering and testing time. Refer to the current LXT318 LXT318 data sheet for complete information on the LXT318 LXT318 transceiver. 1.1 Transmit Line Interface The transmit line interface uses the following parts: 1. Pulse Engineering transformer, P/N PE68646 PE68646 - 1:1.58:2 (one per transceiver) 2. 15 resistors (two per transceiver) Connect them to the Transmit Tip and Ring inputs (pins 13 and 16) of the transceiver as shown above. 1.1.1 Twisted-Pair Cable (120 ) For a twisted-pair cable, use the full 1:2 step-up ratio provided at the end tap. This gives the required 120 impedance. Z = x (step-up ratio)2 = (l5 + l5 ) x 22 = 120 1.1.2 Coaxial Cable (75 ) For a coaxial cable, connect the circuit at the transformer center tap. The 1:1.58 step-up ratio gives a value within 0.2% of the 75 impedance required. Z = x (step-up ratio)2 = (l5 + l5 ) x 1.582 = 74.89 1.2 Circuit Modifications · · · · · Application Note Provides correct impedance match for both 75 coaxial and 120 twisted-pair cables Meets 3 kV isolation requirement of many PTT ministries Standard interface requires one-time design Laboratory engineered and proven design requires minimal in-house testing Readily available parts make building fast and easy 5 LXT318 LXT318 Long-Haul E1 Transceiver Line Interface Design Guide 1.3 Receive Line Interface Figure 1. Receive Line Interface Diagram 1.26 for 75 Coax TRx LXT318 LXT318 RTIP 1.0 for 120 TWP 19 120 1.0 E1 Receive Input From Line 20 RRING P/N PE-65839 PE-65839 The receive line interface uses the following parts: 1. Pulse Engineering transformer, P/N PE65839 PE65839 - 1:1:1.26 (one per transceiver) 2. 120 resistors (one per transceiver) Connect them to the Receive Tip and Ring inputs (pins 19 and 20) of the transceiver as shown above. 1.3.1 Twisted-Pair Cable (120 ) For a twisted-pair cable, use the 1:1 step-down ratio provided at the center tap. This gives the required 120 impedance Z= = 120 = 120 (set-down ratio)2(1)2 1.3.2 Coaxial Cable (75 ) For a coaxial cable, connect the circuit at the transformer center tap. The 1:1.26 step-down ratio gives a value within 1% of the 75 impedance required. Z= 6 = 120 = 75.59 (set-down ratio)2(1.26)2 Application Note