[SI-LIST] Re: VGA/VIDEO: IMPEDANCE & LENGTH

The HSYNC and VSYNC signals have TTL levels.  I often see 300-1k ohm
series resistors on them.  

The analog R,G and B should be 75ohms.  The maximum voltage should be 
0.700 Volts + 0.07 Volts/-0.035 Volts

You can get the VSIS standard from 

Video Electronics Standards Association
920 Hillview Court, Suite 140
Milpitas, CA 95035
408-957-9270


> -----Original Message-----
> From: Chandan [SMTP:chandan_career@xxxxxxxxx]
> Sent: Wednesday, August 01, 2001 9:24 AM
> To:   SI FORUM
> Subject:      [SI-LIST] VGA/VIDEO: IMPEDANCE & LENGTH
> 
> 
> Hi everybody,
> 
> The video interface between a motherboard & a monitor
> typically consists of the following signals:
> 1. RED, GREEN & BLUE
> 2. HSYNC, VSYNC etc.
> 
> My questions: 
> 1. Are there specifications for the characteristic
> impedance of these signals? For e.g., the USB
> specification defines the characteristic impedance
> with which the USB signals must be routed with.
> I'm not too sure, but I think that the RED, GREEN &
> BLUE lines must be routed with a characteristic
> impedance of 37.5 ohms, whereas the HSYNC & VSYNC
> signals must be routed with a trace of characteristic
> impedance of 40 ohms. Could someone clarify please.
> 
> 2. Are there specifications for the maximum length of
> these signals? 
> As of now, I think that the length on the motherboard
> really does not matter. This is because, after the
> signals leave the motherboard, the cable that connects
> to the monitor is at least a foot in length. PLease
> comment.
> 
> Thanks,
> Chandan 
> 
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