LVDS接口的电气特性标准

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### LVDS接口的电气特性标准 #### 一、概述 LVDS（Low Voltage Differential Signaling）是一种低电压差分信号技术，广泛应用于高速数据传输领域。TIA/EIA-644-A是关于LVDS接口电路电气特性的标准文档，由美国电信行业协会（Telecommunications Industry Association，简称TIA）发布，于2001年2月正式推出。该标准旨在为LVDS接口的设计、制造和使用提供统一的技术规范，确保不同厂商的产品之间能够实现良好的互操作性。 #### 二、标准制定背景与目的 随着计算机和通信技术的发展，对于高速数据传输的需求日益增长。LVDS作为一种高效的数据传输方式，其低功耗、高带宽、抗干扰等特性备受青睐。为了满足这一需求并确保LVDS接口的一致性和兼容性，TIA/EIA制定了LVDS接口的电气特性标准——TIA/EIA-644-A。 该标准的主要目的是： 1. **消除误解**：通过标准化电气特性参数，减少制造商和用户之间的沟通障碍。 2. **促进产品互换性**：规定统一的技术指标，使得来自不同制造商的产品可以相互连接和替换。 3. **提升产品质量**：通过对关键性能参数进行规范，帮助制造商提高产品设计水平。 4. **协助用户选择合适的产品**：明确产品的性能特点和技术规格，帮助用户快速准确地选择所需产品。 5. **确保安全合规**：虽然标准不涵盖所有安全问题，但它鼓励用户在使用前评估相关的安全健康实践和法规限制。 #### 三、LVDS电气特性关键指标 根据TIA/EIA-644-A标准，LVDS接口的电气特性主要包括以下几个方面： 1. **工作电压**：LVDS信号的工作电压通常在0.25V到0.5V之间，相较于传统信号技术（如TTL）具有更低的功耗。 2. **差分信号幅度**：标准规定了LVDS信号的典型差分电压幅度为350mV，允许的范围为200mV至400mV。 3. **输出阻抗**：LVDS发送器的输出阻抗应保持在100Ω左右，以匹配接收端的输入阻抗，从而减少信号反射和失真。 4. **数据速率**：LVDS支持从几Mbps到2Gbps甚至更高的数据传输速率，适用于各种应用场景。 5. **共模电压**：LVDS信号的共模电压（即两条信号线的平均电压）应保持在一个稳定的水平，通常为1.2V。 6. **信号完整性和抗干扰能力**：由于采用差分信号传输方式，LVDS接口具有较强的信号完整性和对噪声的免疫力。 #### 四、标准的应用范围 TIA/EIA-644-A标准不仅适用于电信领域的设备，还广泛应用于其他多个行业，包括但不限于： - **计算机硬件**：如服务器主板、图形卡、存储系统等。 - **消费电子**：如高清电视、DVD播放器、数字视频录制设备等。 - **工业控制**：如自动化控制系统、测试测量仪器等。 - **汽车电子**：如车载信息系统、娱乐系统等。 #### 五、结语 TIA/EIA-644-A标准作为LVDS接口电气特性的权威指南，对于确保产品间良好的互操作性和提高整体系统的可靠性具有重要意义。随着技术的进步和市场需求的变化，LVDS技术将继续发展和完善，而TIA/EIA-644-A标准也将适时更新，以适应新的挑战。
TIA/EIA
STANDARD
Electrical Characteristics of Low
Voltage Differential Signaling (LVDS)
Interface Circuits
TIA/EIA-644-A
(Revision of TIA/EIA-644)
FEBRUARY 2001
TELECOMMUNICATIONS INDUSTRY ASSOCIATION
The Telecommunications Industry Association
Represents the Communications Sector of
ANSI/TIA/EIA-644-A-2001
Approved: January 30, 2001
TIA/EIA-644-A
NOTICE
TIA/EIA Engineering Standards and Publications are designed to serve the public interest through
eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and
improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the
proper product for his particular need. Existence of such Standards and Publications shall not in any
respect preclude any member or nonmember of TIA/EIA from manufacturing or selling products not
conforming to such Standards and Publications, nor shall the existence of such Standards and
Publications preclude their voluntary use by those other than TIA/EIA members, whether the standard is
to be used either domestically or internationally.
Standards and Publications are adopted by TIA/EIA in accordance with the American National
Standards Institute (ANSI) patent policy. By such action, TIA/EIA does not assume any liability to any
patent owner, nor does it assume any obligation whatever to parties adopting the Standard or
Publication.
This Standard does not purport to address all safety problems associated with its use or all applicable
regulatory requirements. It is the responsibility of the user of this Standard to establish appropriate
safety and health practices and to determine the applicability of regulatory limitations before its use.
(From Standards Proposal No. 4584, formulated under the cognizance of the TIA TR-30.2 Subcommittee
on DTE-DCE Interfaces Protocols.)
Published by
TELECOMMUNICATIONS INDUSTRY ASSOCIATION 2001
Standards and Technology Department
2500 Wilson Boulevard
Arlington, VA 22201
PRICE: Please refer to current Catalog of
EIA ELECTRONIC INDUSTRIES ALLIANCE STANDARDS and ENGINEERING
PUBLICATIONS or call Global Engineering Documents, USA and Canada
(1-800-854-7179) International (303-397-7956)
All rights reserved
Printed in U.S.A.
ELECTRICAL CHARACTERISTICS OF LOW VOLTAGE DIFFERENTIAL SIGNALING
(LVDS) INTERFACE CIRCUITS
(From TIA/EIA Standard TIA/EIA-644 and Standards Proposal
No. 4584 formulated under the cognizance of TIA
Subcommittee TR-30.2 on Data Transmission Interfaces and Protocols)
Contents Page
1 SCOPE ................................................................................................................................. 1
2 DEFINITIONS, SYMBOLS AND ABBREVIATIONS ..................................................... 2
2.1 Data signaling rate................................................................................................ 2
2.2 DTE......................................................................................................................... 2
2.3 DCE........................................................................................................................ 2
2.4 LVDS...................................................................................................................... 2
2.5 Star (*) .................................................................................................................... 2
3 APPLICABILITY................................................................................................................... 3
3.1 General applicability............................................................................................. 3
3.2 Data signaling rate................................................................................................ 3
4 ELECTRICAL CHARACTERISTICS............................................................................... 5
4.1 Generator characteristics..................................................................................... 5
4.1.1 Full load test measurements............................................................................... 6
4.1.2 Offset voltage and balance measurements........................................................ 7
4.1.3 Short-circuit measurements................................................................................. 8
4.1.4 Output signal waveform ........................................................................................ 8
4.1.5 Dynamic output signal balance............................................................................ 9
4.2 Load characteristics ...........................................................................................10
4.2.1 Receiver input current - voltage measurements...............................................11
4.2.2 Receiver input balance measurements ............................................................11
4.2.3 Terminating receiver input current - voltage measurements and input
impedance measurements ................................................................................12
4.2.4 Receiver input sensitivity measurements .........................................................14
4.2.5 Media termination...............................................................................................15
4.3 Interconnecting media electrical characteristics..............................................16
4.3.1 Cable media........................................................................................................17
4.3.1.1 Maximum dc loop resistance (DCR):................................................................17
4.3.1.2 Characteristic impedance:.................................................................................17
TIA/EIA-644-A
ii
4.3.1.3 Additional parameters........................................................................................17
4.3.2 PC Board trace media .......................................................................................17
4.3.3 Other media.........................................................................................................17
4.4 System parameters.............................................................................................17
4.4.1 Multiple receiver operation.................................................................................17
4.4.2 Failsafe operation...............................................................................................19
4.4.3 Total load limit......................................................................................................19
5 ENVIRONMENTAL CONSTRAINTS.............................................................................20
6 CIRCUIT PROTECTION...................................................................................................21
7 OPTIONAL GROUNDING ARRANGEMENTS.............................................................22
7.1 Signal common (ground)....................................................................................22
7.1.1 Configuration "A".................................................................................................22
7.1.2 Configuration "B".................................................................................................23
7.2 Shield ground - cable applications....................................................................23
A.1 INTERCONNECTING CABLE........................................................................................24
A.1.1 Length...................................................................................................................24
A.1.2 Typical cable characteristics..............................................................................25
A.1.2.1 Parallel interface cable .......................................................................................25
A.1.2.1.1 Parallel cable, physical characteristics..........................................................25
A.1.2.1.2 Parallel cable, electrical characteristics ........................................................25
A.1.2.2 Serial interface cable..........................................................................................26
A.1.2.2.1 Serial cable, physical characteristics.............................................................26
A.1.2.2.2 Serial cable, electrical characteristics...........................................................26
A.1.3 Cable termination................................................................................................26
A.2 CABLE LENGTH VS. DATA SIGNALING RATE GUIDELINES...............................27
B.1 COMPATIBILITY WITH OTHER INTERFACE STANDARDS...................................28
B.1.1 Compatibility with IEEE 1596.3.........................................................................28
B.1.2 Inter-operation with other interface standards..................................................28
B.2 RELATED TIA/EIA STANDARDS..................................................................................29
B.3 OTHER RELATED INTERFACE STANDARDS .........................................................29
TIA/EIA-644-A
iii
FOREWORD
(This foreword is not part of this Standard)
This Standard was formulated under the cognizance of TIA Subcommittee TR-30.2 on
Data Transmission Interfaces.
This Standard was developed in response to a demand from the data communications
community for a general-purpose high-speed interface standard for use in high throughput
DTE-DCE interfaces.
The voltage levels specified in this Standard were specified such that maximum flexibility
would be provided, while providing a low power, high speed, differential interface.
Generator output characteristics are independent of power supply, and may be designed
for standard +5 V, +3.3 V or even power supplies as low as +2.5 V. Integrated circuit
technology may be BiCMOS, CMOS, or GaAs technology. The low voltage (330 mV)
swing limits power dissipation, while also reducing radiation of EMI signals. Differential
signaling provides multiple benefits over single-ended signaling, notably common-mode
rejection, and magnetic canceling.
Additional specifications for multidrop applications have been incorporated into TIA/EIA-
644-A. A full load test measurement for the generator and a balance test of receiver input
current have been added to this revision. A survey of devices conforming to TIA/EIA-644
currently available are able to meet the additional requirements of TIA/EIA-644-A.
This Standard includes two Annexes, both are informative only. Annex A provides
guidelines for application, addressing data signaling rate and cable length issues. Annex B
provides comparison information with other interface standards, and related standards.

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