overkill but done for curiosity

mctrivia

Was curious how close i could make the 12 parallel traces to exactly the same length.

The traces are for hdmi data. I managed to get them to within 3.6pS of each other. kind of silly though since the maximum transfer speed of the controller is 350MHz. and this with tight coupling to the ground plane 5mil below it should be able to do 3GHz.

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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

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SRLM

Shouldn't the bottom set of traces also be curved to some extent? Graphically, if they can be straight then so can the upper traces. Right?

mctrivia

the upper pads are closer together then the bottom pads. without bending the traces like this the bottom trace will arrive 8.3pS before the top trace. with bending like this the bottom trace will arive 3.6pS before the top 6 traces which will all arrive at the same time. Do to space limitations it is not possible to get all 12 traces to arrive at the same time.

this is all a mute point because I forgot i need to put resisters in the middle of each trace and I can easily handle a 33pS delay between first and last bit arriving.

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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.

PJAllen

mctrivia said...
this is all a mute point...

It's moot, not mute.

mctrivia

good point. spell check does not find real words used wrong [noparse]:([/noparse] now if only someone could make a spell check that corrects based on what the word should be.

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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.

WBA Consulting

I'll have to post a pic of one of the boards we do at work that has an insane amount of matching going on with the traces. Makes you think the designer has a DUI on his record (designing under the influence).

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010

mctrivia

I know what you mean. I worked at a high tech video company for a year that made brodcast quality hd hardware. the products with dvi outputs had very funky looking traces to match length and impedance exactly.

On this board I match the HDMI outputs to length exactly but that was easy by placing the driver chip in the right spot. pinout is almost the same as the hdmi header.

I am thinking I will have to drop the 10ohm series resisters do to lack of space. They are intended to help reduce reflections but the only way I can fit them in is to place them on the bottom and use vias which will increase the reflections.

I also need to leave the chip in 12 bit double edge mode which will hopefully work.

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propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.

PJAllen

mctrivia said...
I will have to drop the 10ohm series resisters do to lack of space.

It's " ...due to lack of space," not "do to lack of space."