ch1-Introduction to LVDS
需积分: 5 78 浏览量
2024-04-18
15:22:53
上传
评论
收藏 395KB PDF 举报
Chapter 1
Introduction to LVDS
1
LVDS Owner’s Manual
1.0.0 INTRODUCTION TO LVDS
LVDS stands for Low Voltage Differential Signaling. It is a way to communicate data using a very low
voltage swing (about 350mV) differentially over two PCB traces or a balanced cable.
1.1.0 THE TREND TO LVDS
Consumers are demanding more realistic, visual information in the office and in the home. This is driving
the need to move video, 3-D graphics and photo-realistic image data from camera to PCs and printers
through LAN, phone, and satellite systems to home set top boxes and digital VCRs. Solutions exist
today to move this high-speed digital data both very short and very long distances: on a printed circuit
board (PCB) and across fiber or satellite networks. Moving this data from board-to-board or box-to-box,
however, requires an extremely high-performance solution that consumes a minimum of power, generates
little noise (must meet increasingly stringent FCC/CISPR EMI requirements), is relatively immune to noise
and is inexpensive. Unfortunately existing solutions are a compromise of these four basic ingredients:
performance, power, noise, and cost.
1.2.0 GETTING SPEED WITH LOW NOISE AND LOW POWER
LVDS is a low swing, differential signaling technology which allows single channel data transmission at
hundreds or even thousands of Megabits per second (Mbps). Its low swing and current-mode driver out-
puts create low noise and provide very low power consumption across frequency.
1.2.1 How LVDS Works
Simplified Diagram of LVDS Driver and Receiver Connected via 100Ω Differential Impedance Media
National’s LVDS outputs consist of a current source (nominal 3.5mA) which drives the differential pair line.
The basic receiver has high DC input impedance, so the majority of driver current flows across the 100Ω
termination resistor generating about 350mV across the receiver inputs. When the driver switches, it
changes the direction of current flow across the resistor, thereby creating a valid "one" or "zero" logic state.
Receiver
100Ω
≈350mV
Driver
Current
Source
≈3.5mA
www.national.com/appinfo/lvds/
资源评论
