Analog.com
Analog
Dialogue
Wiki
English
Analog.com
Analog
Dialogue
Wiki
简体中文
EngineerZone
Site
Search
User
Site
Search
User
EngineerZone
Search
Log in
Site
Search
Log in
Home
Blogs ⌵
EngineerZone Spotlight
The Engineering Mind
Browse ⌵
All Groups
All Members
Support ⌵
3D ToF Depth Sensing
Amplifiers
Analog Microcontrollers
Audio
Clock and Timing
Data Converters
Design Tools and Calculators
Direct Digital Synthesis (DDS)
Embedded Vision Sensing
Energy Monitoring and Metering
FPGA Reference Designs
Industrial Ethernet
Interface and Isolation
Low Power RF Transceivers
MEMS Inertial Sensors
Motor Control Hardware Platforms
Optical Sensing
Power By Linear
Processors and DSP
Reference Circuits
RF and Microwave
Switches/Multiplexers
Temperature Sensors
Video
Wide Band RF Transceivers
Wireless Sensor Networks Reference Library
My EZ
More
Cancel
主页
浏览 ⌵
收件箱
个人设置
会员
专区列表
论坛专区 ⌵
放大器专区
精密转换器专区
音频专区
ADE电能计量专区
MEMS和传感器专区
接口和隔离专区
Power 中文专区
ADUC微处理器专区
锁相环专区
开关和多路复用器专区
温度传感器
基准电压源专区
资源库
论坛使用指南
技术支持参考库
在线研讨会
论坛社群活动
论坛激励活动
More
Cancel
Video
Q&A
Improving signal strength on AD9880
Q&A
Discussions
Documents
File Uploads
Video/Images
Tags
Managers
More
Cancel
New
Video requires membership for participation - click to join
State
Verified Answer
Replies
10 replies
Subscribers
86 subscribers
Views
292 views
Users
0 members are here
ad9880
Options
Share
More
Cancel
Related
Improving signal strength on AD9880
JamesL
on Apr 14, 2011
We're using the AD9880 in a design and we find that we are seeing issues on our prototypes which seem to be related to TMDS signal strength. An example setup which shows the problem particularly badly is:
Lenovo X301 DIsplayport output > DP to DVI adaptor > 2m DVI cable > AD9880
Running at 1080p60 (148.5MHz pixel clock) using a generic DVI cable.
We see two kinds of error, one is 'sparkles' - occasional pixels which are the wrong colour and the other is that we sometimes get vsync and hsync signals at the wrong times.
Switching the cable out for a high-quality, thick gauge alternative seems to make the problem much better, but with such a short run, I would hope that this isn't necessary.
Of the 20 units we've tested, the extent of the issue is very varied, the worst examples have such frequent sync signal errors that the image is unusable and the better ones show only a few sparkles per minute and are almost perfect. The same effect can be seen by replacing the AD9880 on a partcular PCB and seeing that the severity of the problem varies significantly, even over devices in the same batch.
Similarly, some video sources are better than others, in particular it seems that laptops with integrated graphics are bad, whether they have native Displayport or HDMI output. The Lenovo X301 is one such bad example, using the Intel GS45 chipset, but the Dell E6400 which uses the GM45 chipset and an extra Nvidia graphics processor is just fine.
We can see the errors on the output of the AD9880 using a scope, so we are fairly sure that the problem is not to do with reception of data later on in the system, but for reference, the 9880 is driving into a Xilinx Spartan 6 LXT using 1v8 I/O.
We have tried experimenting with the PLL registers 0x4D, 0x4E and 0x4F, but they don't seem to fix the problems. Are there any other register settings we can try to improve the reception quality before resorting to looking at hardware changes?
Thanks
James.