OPEN BASE STATION ARCHITECTURE INITIATIVE

Transcription

1 OPEN BASE STATION ARCHITECTURE INITIATIVE Clock and Control Module (CCM) Specification Version.0 Issue.0 ()

2 Preface OBSAI Specification documents are developed within the Technical Working Groups of the Open Base Station Architecture Initiative Special Interest Group (OBSAI SIG). Members of the OBSAI TWG serve voluntarily and without compensation. The specifications developed within OBSAI represent a consensus of the broad expertise on the subject within the OBSAI SIG. Use of an OBSAI Specification is wholly voluntary. The existence of an OBSAI Specification does not imply that there are no other ways to produce, test, measure, purchase, market, or provide other goods and services related to the scope of the OBSAI Specification. Furthermore, the viewpoint expressed at the time a specification is approved and issued is subject to change brought about through developments in the state of the art and comments received from users of the specification. Every OBSAI Specification is subjected to review in accordance with the Open Base Station Architecture Initiative Rules And Procedures. Implementation of all or part of an OBSAI Specification may require licenses under third party intellectual property rights, including without limitation, patent rights (such a third party may or may not be an OBSAI Member). The Promoters of the OBSAI Specification are not responsible and shall not be held responsible in any manner for identifying or failing to identify any or all such third party intellectual property rights. The information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This document is intended for the use of OBSAI Member s customers only for the purposes of the agreement under which the document is submitted, and no part of it may be reproduced or transmitted in any form or means without the prior written permission of OBSAI Management Board. The document has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility when using it. OBSAI Management Board, Marketing Working Group and Technical Working Group welcome customer comments as part of the process of continuous development and improvement of the documentation. The information or statements given in this document concerning the suitability, capacity, or performance of the mentioned hardware or software products cannot be considered binding but shall be defined in the agreement made between OBSAI members. However, the OBSAI Management Board, Marketing Working Group or Technical Working Group have made all reasonable efforts to ensure that the instructions contained in the document are adequate and free of material errors and omissions. OBSAI liability for any errors in the document is limited to the documentary correction of errors. OBSAI WILL NOT BE RESPONSIBLE IN ANY EVENT FOR ERRORS IN THIS DOCUMENT OR FOR ANY DAMAGES, INCIDENTAL OR CONSEQUENTIAL (INCLUDING MONETARY LOSSES), that might arise from the use of this document or the information in it. This document and the product it describes are considered protected by copyright according to the applicable laws. OBSAI logo is a registered trademark of Open Base Station Architecture Initiative Special Interest Group. Issue.0 ()

3 0 0 Other product names mentioned in this document may be trademarks of their respective companies, and they are mentioned for identification purposes only. Copyright Open Base Station Architecture Initiative Special Interest Group. All rights reserved. Users are cautioned to check to determine that they have the latest edition of any OBSAI Specification. Interpretations: Occasionally questions may arise regarding the meaning of portions of standards as they relate to specific applications. When the need for interpretations is brought to the attention of OBSAI, the OBSAI TWG will initiate action to prepare appropriate responses. Since OBSAI Specifications represent a consensus of OBSAI Member s interests, it is important to ensure that any interpretation has also received the concurrence of a balance of interests. For this reason OBSAI and the members of its Technical Working Groups are not able to provide an instant response to interpretation requests except in those cases where the matter has previously received formal consideration. Comments on specifications and requests for interpretations should be addressed to: Peter Kenington Chairman, OBSAI Technical Working Group Linear Communications Consultants Ltd. pbk@linearcomms.com Issue.0 ()

4 Contents Summary of changes... Scope... General.... Topology and Dimensioning Requirements.... Hot Insertion and Removal.... Signal Naming Conventions...0. Connector Naming and Orientation... CCM Interfaces.... Signal List.... Signal Specification..... Common Signals..... CCM Specific Signals..... Redundancy Signals..... CCM Unspecified Signals..... CCM Power Signals... CCM Pin Assignments.... J Data Connector.... J Data Connector.... Power Connector... Glossary.... Abbreviations.... Definition of Terms... References.... OBSAI.... IEEE.... ANSI... Issue.0 ()

5 Figures Figure - BTS Reference Architecture... Figure - Signal Direction Definition... Figure - Connector Positions and Naming (Module Rear View)... Figure - T OUT_SYNC Timing... Figure - Redundancy Connection Scheme... Issue.0 ()

6 List of Tables Table - CCM Signal Abbreviations...0 Table - CCM Interface signal list... Table - Reference Clock Electrical Parameters... Table - PPS Clock Electrical Parameters... Table - Aux Clock Electrical Parameters... Table - System Clock Electrical Parameters...0 Table - System Synchronization Signal Electrical Parameters... Table - Data Connector J Pin Assignment (module rear view)... Table - Data Connector J Pin Assignment (rear view)... Table - CCM power connector P Pin Assignment... Table - CCM optional power connector P Pin Assignment... Issue.0 ()

7 Summary of changes Version Approved by Date 0.0 Draft -Dec Draft -Dec Draft -Feb Draft -Feb Draft -Mar Draft -Mar Draft -Apr Draft -May Draft -May Draft -June Draft -June-00.0 OBSAI Management Board th July 00 Issue.0 ()

8 Scope This document specifies the base transceiver system (BTS) internal interfaces (i.e., System Interfaces) of the OBSAI Clock and Control Module (CCM). It defines the CCM s physical implementation of OBSAI reference point RP and the required interconnection scheme to other BTS modules as illustrated in Figure - below. RP RP Iub or Abis Transport Block BaseBand Block RF Block Power RP Proprietary Block RP Control and Clock Block Control Traffic Clock Power Figure - BTS Reference Architecture Issue.0 ()

9 General This specification focuses on the physical interface requirements of the CCM. The actual BTS and CCM designs are out of the scope of this document. Guidelines for implementation are given where appropriate.. Topology and Dimensioning Requirements The BTS internal interface provided by the CCM supports the following functions: Ä Ä Internal Networking functions via RP Synchronization functions via RP 0 Internal Networking functions are based on LAN concepts using Ethernet as the Layer protocol. Each module in the shelf has a dedicated link to the fabric. The CCM distributes system clocks and synchronization bursts to other modules in one shelf using a star topology. Clock and Control Module redundancy is supported optionally by a second CCM, forming the center of a second clock and synchronization network (double star topology). See section.. for details on redundancy. The CCM optionally supports shelf extension, with a point-to-point connection to a clock and synchronization network in a second shelf. See the OBSAI RP Specification [OBSAI RP] for details on shelf extension. 0. Hot Insertion and Removal All signals shall support hot insertion and removal. Hot insertion is supported on the module by delayed (insertion) and early (removal) switch on/off of the power supply by means of a last mating enable pin at the power connector. Every source and sink of a signal shall survive without any damage, if the connected signal is within its specified operating voltage range. Issue.0 ()

10 . Signal Naming Conventions All signal names start with a --letter abbreviation that describes the general function of the signal group. Abbreviation Full Name Comment MA Module Address - SA Shelf Address - MNC Module Not Connected Not Connected on Module FP Fabric Port - SCLK System Clock - RCLK Reference Clock - SYNC Synchronization Signal - PPSCLK PPS Clock - AUXCLK Auxiliary Clock - CCMUS CCM Unspecified - RC Redundancy Control - RCL Redundancy Communication Link - GND Ground Digital Ground BPNC Backplane Not Connected Not Connected on Backplane Table - CCM Signal Abbreviations 0 The signal name abbreviation is followed by a numerical index to distinguish between instances of a signal inside a signal group. The index starts with the value 0. Additionally a direction indication is attached for signal groups with receive (_RX), transmit (_TX), or bidirectional (_BI) signals, if there is a need to distinguish between them. The direction is derived from the physical characteristics at the module boundary. The direction of signals not explicitly indicated by the signal name is specified in the signal list (section.), or left unspecified intentionally. Issue.0 0 ()

11 Module RX TX BI Figure - Signal Direction Definition A signal group supporting more than one differential pair (e.g. 000 Base-T) uses alphabetic letters starting with DA (e.g. DA, DB, DC, ). Finally, differential pair signals are denoted by a trailing + (positive) or (negative) symbol. The following rule applies: Signal Name Abbreviation [Numerical Index] [_RX;_TX;_BI][DPair Index] [+;-] Issue.0 ()

12 . Connector Naming and Orientation Definitions: Ä Ä Ä Ä Female connectors use the reference designator prefix J Male connectors use the reference designator prefix P Mechanical guiding pins use the reference designator prefix G Mechanical guiding holes use the reference designator prefix H A numerical index follows the designator prefix. The following rule applies to the module: Prefix [Module Index] 0 This concept also applies to the backplane connectors. Although this is not within the scope of this specification, it is nevertheless recommended to follow this guidance. In addition to the module index, the backplane has a slot index, which references the slot position. The following rule applies to the backplane: Prefix [Module Index] [Slot Index] Figure - shows the module connector naming. Issue.0 ()

13 PCB P P Optional Power Connector Power Connector J Data Connector (with Guide) J Optional Data Connector Figure - Connector Positions and Naming (Module Rear View) Issue.0 ()

14 CCM Interfaces. Signal List The CCM signal groups and the expected peer modules are listed below: No Signal Group Peer Module Comment Direction Technology Common Signals SA[0..] Not applicable Shelf address ( bit) I - MA[0..] Not applicable Module address ( bit) I - FP[0..]_TX[+,-] TM Fabric Port 0 and O 00 Base-TX FP[0..]_RX[+,-] TM Fabric Port 0 and I 00 Base-TX BPNC Not applicable Proprietary test and debug signals unspecified unspecified GND Not applicable Digital Ground - - CCM Specific Signals RCLK[0..][+,-] TM[0..] khz Reference Clock I LVDS RA[+,-] CCM Redundancy Communication Link RB[+,-] CCM Redundancy Communication Link unspecified unspecified 00 Ohm diff. 00 Ohm diff. 0 RC[0..] CCM Redundancy Control unspecified unspecified RD[0..] CCM Redundancy Control unspecified unspecified SCLK[0..0][+,-] Not identified System Clock Port O LVDS SYNC[0..0][+,-] Not identified Synchronization Port O LVDS PPSCLK[0..][+,-] PM Pulse-per-second I LVDS Issue.0 ()

15 AUXCLK[0..][+,-] Not identified 0MHz Auxiliary Clock I LVDS GND Not applicable Digital Ground - - MNC Not applicable No Connection on Module - - CCM Unspecified Signals CCMUS[0..] Not applicable Proprietary Signals unspecified - CCM Power Signals PWR_POS Not applicable Supply Positive - Power 0 PWR_NEG Not applicable Supply Negative - Power PWR_ENA Not applicable Power Enable I - GND Not applicable Digital Ground - - Table - CCM Interface signal list Note : Could be any other module Note : Peer is the backup CCM module in the protection group. Issue.0 ()

16 . Signal Specification This chapter specifies the CCM interface signals at the CCM boundary. The data and power connector signals are differentiated in groups: Ä Ä Ä Ä Common Signals CCM Specific Signals CCM Unspecified Signals Power If necessary, additional requirements for the implementation are given in the relevant signal subchapter... Common Signals Common signals are common to all modules and shall be supported. Common Signals are assigned to fixed pin positions within the data connector J, which is present in all modules. Since the CCM sources the System Clocks and Synchronization Signals to other modules, these are not included in the Common signal group of the CCM.... Module and Shelf address The module (MA[0..]) and shelf address signals (SA[0..]) are used to give the module a unique hardwired address related to the shelf and slot position of the module. The CCM shall pull the address pins up. An address bit logic one is indicated by leaving the address pin unconnected on the backplane. A logic zero is indicated through connecting the respective pin to logic ground on the backplane. The address signals are static.... Ethernet Fabric Ports The common fabric ports 0 and are available on every module in the shelf. On the CCM module these ports are Fast Ethernet [00Base-TX] according to [IEEE 0.] clause... CCM Specific Signals CCM specific signals are specific to the CCM and shall be supported. CCM specific signals are assigned to fixed pin positions at the data connector J. Issue.0 ()

17 0... Reference Clock Inputs The Transport Modules in the shelf can provide.000khz reference clock signals to the CCM. These clocks can be used as frequency references for the system clock. The reference clock links in the system are point-to-point. The CCM shall have two differential clock inputs - one from each of the two TMs, which together form a redundant pair. The reference clock timing parameters are specified according to the OBSAI RP Specification [OBSAI RP]. The maximum jitter and wander of the Reference Clock is determined by those qualities of the external network connected to the TM. The electrical receiver characteristic of the CCM Reference Clock input shall follow the LVDS standard ANSI/TIA/EIA--A [ANSI]. The CCM shall terminate these backplane clock links with a differential impedance of 00 Ä Å 0%. Parameter Symbol Min Typical Max Unit Receiver Input Threshold V TH - - Å 00 mv Differential Input Voltage V ID Å 00 - Å 00 mv Input Current (Power On) I IN_ON - - Å 0 ua Input Current (Power Off) I IN_OFF - - Å 0 ua Input Voltage Range V IN 0 -. V Differential Input Impedance Z IN Ä Table - Reference Clock Electrical Parameters 0 In the CCM power-down state the receiver input shall be in a high impedance state.... PPS Clock Inputs Proprietary Modules in the shelf can provide pulse-per-second clocks for the CCM module. This clock can be used as a time reference for Synchronization Bursts as well as a frequency reference for System Clocks. The pulse-per-second clock links (PPSCLK) are point-to-point. Issue.0 ()

18 The CCM shall have two differential PPSCLK inputs - for up to two PM's, which together could form a redundant pair. The pulse-per-second clock timing parameters are specified according to the RP Specification [OBSAI RP]. PPS timing is referenced to the clock rising edge. The electrical receiver characteristic of the CCM PPSCLK input shall follow the LVDS standard ANSI/TIA/EIA--A [ANSI]. The CCM shall terminate the PPS links with a differential impedance of 00 Ä Å 0%. Parameter Symbol Min Typical Max Unit Receiver Input Threshold V TH - - Å 00 mv Differential Input Voltage V ID Å 00 - Å 00 mv Input Current (Power On) I IN_ON - - Å0 ua Input Current (Power Off) I IN_OFF - - Å0 ua Input Voltage Range V IN 0 -. V Differential Input Impedance Z IN Ä Table - PPS Clock Electrical Parameters 0 In the CCM power-down state the receiver input shall be in a high impedance state.... Auxiliary Clock Inputs This clock can be used as a frequency reference for the System Clock. The Auxiliary clock links (AUXCLK) are point-to-point. The CCM shall have two differential Aux clock inputs - for up to two sources, which together could form a redundant pair. These inputs shall support a 0MHz auxiliary clock, and may support other reference frequencies. The electrical receiver characteristics of the CCM auxiliary clock input shall follow the LVDS standard ANSI/TIA/EIA--A [ANSI]. The CCM shall terminate the Aux links with a differential impedance of 00 Ä Å 0%. 0 Issue.0 ()

19 Parameter Symbol Min Typical Max Unit Receiver Input Threshold V TH - - Å 00 mv Differential Input Voltage V ID Å 00 - Å 00 mv Input Current (Power On) I IN_ON - - Å0 ua Input Current (Power Off) I IN_OFF - - Å0 ua Input Voltage Range V IN 0 -. V Differential Input Impedance Z IN Ä Table - Aux Clock Electrical Parameters 0 In CCM power-down state the receiver input shall be in high impedance state.... System Clock Outputs The CCM shall provide a 0.MHz System Clock (SCLK) to other modules in the shelf. It can also be extended to another shelf through an extension module. This System Clock can be used as a frequency reference for other modules. While inputs khz, AUXCLK, or PPSCLK are accurate to 0.0 parts per million (PPM), the System Clock Outputs shall meet the System Clock parameters specified in the RP Specification [OBSAI RP]. In the absence of a timing reference (hold-over), the System Clock Outputs shall drift no more than 0.0 PPM in hours. The System Clocks are delivered through multiple point-to-point links. The System Clock timing parameters are specified in the RP Specification [OBSAI RP]. The electrical transmitter characteristics of the CCM System Clock output shall follow the LVDS standard ANSI/TIA/EIA--A [ANSI]. The output impedance for the System Clock signal should be 00 Ä Å 0%. Issue.0 ()

20 Parameter Symbol Min Typical Max Unit Transmitter Differential Output Voltage V OD - mv Transmitter Offset Voltage V OS. -. V Input Current (Power Off) I IN_OFF - - Å0 ua System Clock Rise/Fall time t RISE/FALL - - ns System Clock to Clock Skew t CC - - ns Table - System Clock Electrical Parameters 0 In the CCM power-down state, the transmitter output shall be in a high impedance state.... System Synchronization Signal Outputs The System Synchronization Signal (SYNC) provides frame timing and time stamping in the form of synchronization bursts. These bursts of information are synchronous to the System Clock and have timing parameters and data formatting as specified in the RP Reference Point Specification [OBSAI RP]. The System Synchronization Signals are delivered through multiple point-to-point links. The electrical transmitter characteristics of the System Synchronization Signals shall follow the LVDS standard ANSI/TIA/EIA--A [ANSI]. The output impedance for the System Synchronization Signal should be 00 Ä Å 0%. In addition to the timing and data formatting requirements indicated in [OBSAI RP], the CCM shall satisfy the T OUT_SYNC setup timing parameter as described in Figure -and Table -. Issue.0 0 ()

21 SYNC T OUT_SYNC =-.ns (min), +.ns (max) SCLK Figure - T OUT_SYNC Timing Parameter Symbol Min Typical Max Unit Transmitter Differential Output Voltage V OD - mv Transmitter Offset Voltage V OS. -. V Input Current (Power Off) I IN_OFF - - Å0 ua System Clock (SCLK) to System Synchronization Signal (SYNC) Delay t QUT_SYNC ns Table - System Synchronization Signal Electrical Parameters In the CCM power-down state the transmitter output shall be in a high impedance state. Issue.0 ()

22 0.. Redundancy Signals Redundancy Signals form a link between two peer CCM's. They comprise Redundancy Control Signals (RC[0..], RD[0..]) and Redundancy Communication Link Signals (RA+/-, RB+/-). If redundancy is supported, the interconnection scheme shown in Figure - shall be applied. It is expected that modules in a redundant pair are from the same type and vendor. Therefore, the functional and timing characteristics of the Redundancy Signals are not specified. The Redundancy Communication Link on the CCM shall be 00 Ä differential pair. The electrical characteristics of the Redundancy Signals are not specified. In the CCM power-down state, the Redundancy Control Signals shall be in a high impedance state. Issue.0 ()

23 CCM Module CCM Module RA+ RA- RB+ RB- RA+ RA- RB+ RB- RC0 RC0 RC RC RC RC RC RC RD0 RD0 RD RD RD RD RD RD Figure - Redundancy Connection Scheme 0.. CCM Unspecified Signals CCM Unspecified Signals are optional. Their functional and electrical characteristics are not specified. If present, CCM Unspecified Signals shall be assigned to fixed pin positions on the data connectors J and J. Connecting CCM Unspecified Signals may cause incompatibility with certain backplane configurations... CCM Power Signals For power requirements and limits, see the OBSAI System Reference Document [OBSAI System] Issue.0 ()

24 CCM Pin Assignments. J Data Connector The data connector is specified in the OBSAI System Reference Document [OBSAI System] Appendix C. Coding style shall be used. J f e d c b a SA0 BPNC BPNC BPNC BPNC BPNC SA BPNC BPNC BPNC BPNC BPNC SA GND GND BPNC GND GND GND MNC FP_TX+ GND MNC FP0_TX+ GND MNC FP_TX- GND MNC FP0_TX- GND MNC FP_RX+ GND MNC FP0_RX+ GND MNC FP_RX- GND MNC FP0_RX- AUXCLK+ MA MA MA MA MA0 AUXCLK- GND BPNC GND BPNC GND 0 BPNC AUXCLK0+ GND RCLK+ GND RCLK0+ BPNC AUXCLK0- GND RCLK- GND RCLK0- CCMUS0 GND PPSCLK0+ GND PPSCLK0+ GND CCMUS GND PPSCLK- GND PPSCLK- GND CCMUS CCMUS GND RB+ GND RA+ RC RC RC RB- RC0 RA- RD RD RD GND RD0 GND CCMUS CCMUS GND SYNC0+ GND SCLK0+ CCMUS GND GND SYNC0- GND SCLK0- GND SYNC+ SYNC+ GND SCLK+ SCLK+ 0 GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC+ SYNC+ GND SCLK+ SCLK+ GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC+ SYNC+ GND SCLK+ SCLK+ GND SYNC- SYNC- GND SCLK- SCLK- Table - Data Connector J Pin Assignment (module rear view) Note : Common Signals (section..) are indicated by an underline. Issue.0 ()

25 Note : These signals are not part of the common signal group, since the CCM sources SCLK and SYNC.. J Data Connector J f e d c b a GND SYNC+ SYNC+ GND SCLK+ SCLK+ GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC0+ SYNC+ GND SCLK0+ SCLK+ GND SYNC0- SYNC- GND SCLK0- SCLK- GND SYNC+ SYNC+ GND SCLK+ SCLK+ GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC+ SYNC+ GND SCLK+ SCLK+ GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC+ SYNC+ GND SCLK+ SCLK+ 0 GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC+ SYNC+ GND SCLK+ SCLK+ GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC0+ SYNC+ GND SCLK0+ SCLK+ GND SYNC0- SYNC- GND SCLK0- SCLK- GND SYNC+ SYNC+ GND SCLK+ SCLK+ GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC+ SYNC+ GND SCLK+ SCLK+ GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC+ SYNC+ GND SCLK+ SCLK+ 0 GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC+ SYNC+ GND SCLK+ SCLK+ GND SYNC- SYNC- GND SCLK- SCLK- GND SYNC0+ SYNC+ GND SCLK0+ SCLK+ GND SYNC0- SYNC- GND SCLK0- SCLK- Table - Data Connector J Pin Assignment (rear view) Issue.0 ()

26 . Power Connector CCM modules shall be equipped with a power connector P (OBSAI Sequenced), as specified in Table -. P Signal PWR_POS PWR_ENA PWR_NEG GND Table - CCM power connector P Pin Assignment For additional supply current, CCM modules may optionally be equipped with a second power connector P (OBSAI Sequenced or OBSAI Non-sequenced), as specified in Table -. P Signal PWR_POS PWR_POS PWR_NEG PWR_NEG 0 Table - CCM optional power connector P Pin Assignment Note : Pins and can only be used with the OBSAI Non-sequenced connector. Issue.0 ()

27 Glossary. Abbreviations For the purposes of the present document, the following abbreviations apply: ABBREVIATION DESIGNATION BBM Base Band Module BTS Base Transceiver Station CCM Clock and Control Module ESD Electrostatic Discharge GND Ground LVDS Low Voltage Differential Signaling OBSAI Open Base Station Architecture Initiative PM Proprietary Module RFM Radio Frequency Module RP Reference Point RP Reference Point RP Reference Point TM Transport Module 0. Definition of Terms For the purposes of the present document, the following terms and definitions apply: Common Signals: Common Signals are common to all modules and shall be supported. Common Signals are assigned to fixed pin positions within the Data Connector(s) which are present at all modules. Module Type Specific Signals: Module Type Specific Signals are specific to a certain module types (TM, CCM, BBM, RFM, PM) and shall be supported. Module Type specific Signals shall be assigned to fixed pin positions within the Data Connector(s). Issue.0 ()

28 Module Type Unspecified Signals: Module Type Unspecified Signals are optional. Their functional and electrical characteristics are not specified. If present, Module Type Unspecified Signals shall be assigned to a range of pin positions within the Data Connector(s). The range of pin positions shall be fixed for a certain module type, but may differ between module types. Signal Group: A group of signals forming a functional entity e.g. a fabric port. 0 Issue.0 ()

29 References. OBSAI [OBSAI System] OBSAI System Reference Document V.0 [OBSAI RP] OBSAI Reference Point Specification V.0 [OBSAI RP] OBSAI Reference Point Specification V.0. IEEE [IEEE 0.] IEEE Std, 0., Local and Metropolitan Area Networks, 00.. ANSI 0 [ANSI] ANSI/TIA/EIA--A, Electrical Characteristics of Low Voltage Differential Signaling (LVDS) Interface Circuits Issue.0 ()