[SI-LIST] Re: Driver slew rates
- From: steve weir <weirsi@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 25 Nov 2013 04:43:21 -0800
Reflection is a function of an impedance discontinuity. If you do not
want old signal energy rattling around in your transmission channel then
you need to reduce channel Q. IE you need to absorb energy. The
cleanest results occur when you absorb energy at one end of the line or
the other or preferably both.
Quarter wave structures make wonderful resonators and couplers. They do
not absorb energy per-se.
Steve.
On 11/25/2013 4:21 AM, ravikumar potluri wrote:
> Hello everyone, The problem was with the length of the TL with respect to
> the rise time of the driver. The length of TL has to be some multiples of
> quarter wavelengths inorder to reduce the reflections. There is no problem
> with the IBIS files. I thank you all very much for helping me to understand
> the problem.
> Regards,
> Ravi
>
>
> On Sun, Nov 24, 2013 at 8:41 AM, Muranyi, Arpad
> <Arpad_Muranyi@xxxxxxxxxx>wrote:
>
>> Ravi,
>>
>> Slew rate usually refers to the slope of the voltage (dV/dt) on
>> the output of a driver. For that reason a receiver doesn't have
>> slew rate.
>>
>> Reflections are caused by impedance discontinuities (mismatches)
>> in the channel. If you have a lot of reflections and not much
>> loss (damping), you can get a lot of ringing (reflections bouncing
>> back and forth in the T-line). But ringing can also be caused by
>> LC effects even if there are no T-lines lines present between the
>> driver and receiver. Check if your models have lumped RLC package
>> models.
>>
>> I hope this helps,
>>
>> Arpad
>> ====================================================================
>>
>> -----Original Message-----
>> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>> On Behalf Of ravikumar potluri
>> Sent: Saturday, November 23, 2013 9:49 AM
>> To: si-list@xxxxxxxxxxxxx
>> Subject: [SI-LIST] Driver slew rates
>>
>> Hello friends,
>> If the slew rate of driver is much higher than the slew rate of receiver
>> does this cause reflections on the transmission line?
>>
>>
>> I am simulating ADS62P49, 250 MSPS ADC chip (Driver) with Spartan 3A-DSP
>> (Reciever). I see lot of ringing at the output even when the chips are
>> connected directly with termination in between and with no transmission
>> line.
>>
>> Could someone explain this?
>>
>> Thanks and Regards,
>> Ravi
>>
>>
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