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EMI filters for hsync and vsync.
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Topic: EMI filters for hsync and vsync. (Read 834 times)
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fabiodl
Frequent Contributor
Posts: 282
EMI filters for hsync and vsync.
«
on:
February 24, 2022, 10:00:36 am »
I noticed that the dreamcast vga box (pics here
https://shmups.system11.org/viewtopic.php?p=867369#p867369
)
use emi filters in series with the hsync and vsync lines of the VGA.
I am replicating the circuit. What EMI filter would you use?
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Terry Bites
Super Contributor
Posts: 2471
Country:
Recovering Electrical Engineer
Re: EMI filters for hsync and vsync.
«
Reply #1 on:
February 24, 2022, 11:46:12 am »
Hi
Your link is to a whole blog- no chance of finding the specific schematic.
Are you referring to the pull-up reistors and diodes on the sync lines?
They are simply there to clamp the DC levels of the sync pulses.
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fabiodl
Frequent Contributor
Posts: 282
Re: EMI filters for hsync and vsync.
«
Reply #2 on:
February 24, 2022, 01:12:18 pm »
The link is to the post which contains pictures of the board.
The H and V lines are, indeed, protected by a diode.
One EMI filter is in series, just before the vga connector, of each of the h and v lines.
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Terry Bites
Super Contributor
Posts: 2471
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Recovering Electrical Engineer
Re: EMI filters for hsync and vsync.
«
Reply #3 on:
February 24, 2022, 04:41:39 pm »
I tried you link again. Takes me to a page full of stuff that I'm not going to bother sieving.
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dmills
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Re: EMI filters for hsync and vsync.
«
Reply #4 on:
February 25, 2022, 07:23:52 pm »
I also got a page of rather confused discussion of prehistoric game console video outputs...
The sync outputs are likely driven by some sort of digital logic output which will have a rather fast edge rate in comparison to the output of whatever video DAC the thing uses, I think I would probably throw some filtering on there if I was designing it.
Probably just some sort of small ferrite bead and a 100pF cap, should be fine.
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fabiodl
Frequent Contributor
Posts: 282
Re: EMI filters for hsync and vsync.
«
Reply #5 on:
February 26, 2022, 07:26:50 am »
There's no DAC in the device itself, it goes straight into the monitor.
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