Resistive terminations are more desirable because they absorb energy
rather than transfer it to a different part of the line. The energy
from the driver eventually has to be dissipated in a resistance somewhere.
regards,
Larry
> From: [email protected]
> X-Lotus-FromDomain: NATURAL MICROSYSTEMS
> To: [email protected]
> cc: [email protected]
> Date: Wed, 10 Jun 1998 09:06:17 -0400
> Subject: Re: [SI-LIST] : Diode Termination of Transmission Lines
> Mime-Version: 1.0
>
>
> My experience with Diode termination:
>
> ? Schottky Diode Termination
> In some cases it can be expedient to use Schottky diodes or
> fast-switching silicon diodes to terminate lines. The diode
> switching time must be at least four times as fast as the signal
> rise time. Where line impedances are not well defined, as in
> breadboards and backplanes, the use of diode termination is
> convenient and can save time.
> The Schottky diode's low forward voltage, V(subscript: f)
> (typically 0.3 to 0.45V), clamps the input signal to a V
> (subscript: f) below ground (lower diode) and V(subscript: cc)+V
> (subscript: f) (upper diode). This significantly reduces signal
> undershoot and overshoot. Some applications may not require both
> diodes.
> ? The advantages of diode termination are:
> 1. Impedance matched lines are not required
> 2. The diodes replace terminating resistors or RC termination
> 3. The diodes' clamping action reduces overshooting and undershooting
> 4. Although diodes cost more than resistors, the total cost of layout
> might be less because a precise, controlled transmission-line
> environment is not required
> 5. If ringing is discovered to be a problem during system debug, the
> diodes can be easily added.
>
> Wojciech
>
>
>
>
>
> [email protected] on 06/10/98 06:09:39 AM
>
> To: [email protected]
> cc: (bcc: Wojciech Babij)
> Subject: [SI-LIST] : Diode Termination of Transmission Lines
>
>
>
>
>
>
> Hi,
>
> Might anyone be able to point me in the direction of some PRACTICAL
> application information on using Diode Termination on Transmission
> Lines. In particular for PCB1/Ribbon Cable/PCB2 interconnection as
> well as one side of a PCB to the other side.
>
> Most of the information that I have seen so far doesn't do anything
> more than give a brief overview. I was hoping on getting information
> on the diodes used and any of the pitfalls.
>
> Thanks
>
> Peter Baxter
>
>
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