In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V
and -0.7V.
In my design with C6713, maximum overshoot and undershoot on input pins is 4.4V
and -1V.
Violation is 0.4V, is it dangerous for my design?
How can I reduce overshoot and undershoot without any change in trace delay?
Regards
Zahra
Overshoot on data bus
Started by ●May 18, 2008
Reply by ●May 18, 20082008-05-18
Zahra-
> In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V and -0.7V.
> In my design with C6713, maximum overshoot and undershoot on input pins is 4.4V and -1V.
>
> Violation is 0.4V, is it dangerous for my design?
Which pins?
Does the 4.4V figure come from simulation of your layout? If from simulation, are
you using IBIS models?
> How can I reduce overshoot and undershoot without any change in trace delay?
You can use series R. I thought you were already using these?
-Jeff
> In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V and -0.7V.
> In my design with C6713, maximum overshoot and undershoot on input pins is 4.4V and -1V.
>
> Violation is 0.4V, is it dangerous for my design?
Which pins?
Does the 4.4V figure come from simulation of your layout? If from simulation, are
you using IBIS models?
> How can I reduce overshoot and undershoot without any change in trace delay?
You can use series R. I thought you were already using these?
-Jeff
Reply by ●May 19, 20082008-05-19
I used IBIS model for DSP, SDRAM, flash also series resistor in data bus, and
address bus.
Overshoot is on data bus when SDRAM is driver and C6713 is load.
Maximum overshoot and undershoot on input pins is 4.4V and -1V in data bus (0-31).
Regards
Zahra
In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V and -0.7V.
>In my design with C6713, maximum overshoot and undershoot on input pins is 4.4V and -1V.
>
>Violation is 0.4V, is it dangerous for my design?
>How can I reduce overshoot and undershoot without any change in trace delay?
>
>Regards
>Zahra
Overshoot is on data bus when SDRAM is driver and C6713 is load.
Maximum overshoot and undershoot on input pins is 4.4V and -1V in data bus (0-31).
Regards
Zahra
In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V and -0.7V.
>In my design with C6713, maximum overshoot and undershoot on input pins is 4.4V and -1V.
>
>Violation is 0.4V, is it dangerous for my design?
>How can I reduce overshoot and undershoot without any change in trace delay?
>
>Regards
>Zahra
Reply by ●May 19, 20082008-05-19
Zahra,
how did you measure overshots? With a standard oscilloscope probe the
overshot may be caused mainly by the probe GND connection (the "pigtail"),
and not by your layout! A reliable measurement requires to use a GND clip
on the probe.
Overshots are efficiently dampened by series resistors (22..47 ohms),
located close to the source. This will add only a few picoseconds delay.
Also make sure to use a good low impedance GND plane without too many
separations. Keep the PCB traces to blocking capacitors as short as
possible: the inductance of these traces is significant for high switching
frequencies, even if the trace length is only a few millimeters.
Regards,
Adolf Klemenz, D.SignT
At 05:19 18.05.2008 -0400, z...@yahoo.com wrote:
>In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V
>and -0.7V.
>In my design with C6713, maximum overshoot and undershoot on input pins is
>4.4V and -1V.
>
>Violation is 0.4V, is it dangerous for my design?
>How can I reduce overshoot and undershoot without any change in trace delay?
>
>Regards
>Zahra
how did you measure overshots? With a standard oscilloscope probe the
overshot may be caused mainly by the probe GND connection (the "pigtail"),
and not by your layout! A reliable measurement requires to use a GND clip
on the probe.
Overshots are efficiently dampened by series resistors (22..47 ohms),
located close to the source. This will add only a few picoseconds delay.
Also make sure to use a good low impedance GND plane without too many
separations. Keep the PCB traces to blocking capacitors as short as
possible: the inductance of these traces is significant for high switching
frequencies, even if the trace length is only a few millimeters.
Regards,
Adolf Klemenz, D.SignT
At 05:19 18.05.2008 -0400, z...@yahoo.com wrote:
>In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V
>and -0.7V.
>In my design with C6713, maximum overshoot and undershoot on input pins is
>4.4V and -1V.
>
>Violation is 0.4V, is it dangerous for my design?
>How can I reduce overshoot and undershoot without any change in trace delay?
>
>Regards
>Zahra
Reply by ●May 19, 20082008-05-19
Zahra,
On 5/19/08, z...@yahoo.com wrote:
>
> I used IBIS model for DSP, SDRAM, flash also series resistor in data
> bus, and address bus.
> Overshoot is on data bus when SDRAM is driver and C6713 is load.
> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data bus
> (0-31).
>
What happens if you increase the data bus series resistors 20-25%??
What value resistor did you start with??
Are you modeling a board with a ground plane or a 2 layer board??
mikedunn
Regards
> Zahra
>
> In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V
> and -0.7V.
> >In my design with C6713, maximum overshoot and undershoot on input pins is
> 4.4V and -1V.
> >
> >Violation is 0.4V, is it dangerous for my design?
> >How can I reduce overshoot and undershoot without any change in trace
> delay?
> >
> >Regards
> >Zahra
--
www.dsprelated.com/blogs-1/nf/Mike_Dunn.php
On 5/19/08, z...@yahoo.com wrote:
>
> I used IBIS model for DSP, SDRAM, flash also series resistor in data
> bus, and address bus.
> Overshoot is on data bus when SDRAM is driver and C6713 is load.
> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data bus
> (0-31).
>
What happens if you increase the data bus series resistors 20-25%??
What value resistor did you start with??
Are you modeling a board with a ground plane or a 2 layer board??
mikedunn
Regards
> Zahra
>
> In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V
> and -0.7V.
> >In my design with C6713, maximum overshoot and undershoot on input pins is
> 4.4V and -1V.
> >
> >Violation is 0.4V, is it dangerous for my design?
> >How can I reduce overshoot and undershoot without any change in trace
> delay?
> >
> >Regards
> >Zahra
--
www.dsprelated.com/blogs-1/nf/Mike_Dunn.php
Reply by ●May 19, 20082008-05-19
Zahra-
> I used IBIS model for DSP, SDRAM, flash also series resistor in data bus, and address bus.
> Overshoot is on data bus when SDRAM is driver and C6713 is load.
> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data bus (0-31).
Mike's questions to you are good ones. Also I would ask where you placed the series R -- maybe close to the DSP? If
so, try placing in the middle of the trace.
** Please don't cut out text from my reply when you answer. If you do that, the thread is not usable by others in the
future, and I can no longer help you. **
-Jeff
> In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V and -0.7V.
>>In my design with C6713, maximum overshoot and undershoot on input pins is 4.4V and -1V.
>>
>>Violation is 0.4V, is it dangerous for my design?
>>How can I reduce overshoot and undershoot without any change in trace delay?
>>
>>Regards
>>Zahra
> I used IBIS model for DSP, SDRAM, flash also series resistor in data bus, and address bus.
> Overshoot is on data bus when SDRAM is driver and C6713 is load.
> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data bus (0-31).
Mike's questions to you are good ones. Also I would ask where you placed the series R -- maybe close to the DSP? If
so, try placing in the middle of the trace.
** Please don't cut out text from my reply when you answer. If you do that, the thread is not usable by others in the
future, and I can no longer help you. **
-Jeff
> In C6713' datasheet, maximum overshoot and undershoot on input pins is 4V and -0.7V.
>>In my design with C6713, maximum overshoot and undershoot on input pins is 4.4V and -1V.
>>
>>Violation is 0.4V, is it dangerous for my design?
>>How can I reduce overshoot and undershoot without any change in trace delay?
>>
>>Regards
>>Zahra
Reply by ●May 20, 20082008-05-20
Mikdunn-
>Zahra,
>On 5/19/08, z...@yahoo.com wrote:
>>
>> I used IBIS model for DSP, SDRAM, flash also series resistor in data
>> bus, and address bus.
>> Overshoot is on data bus when SDRAM is driver and C6713 is load.
>> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data bus
>> (0-31).
>>
>What happens if you increase the data bus series resistors 20-25%??
some data bus(D0-15 and D24-31) with 33ohm series resistor damped overshoot.
but in D16-23, overshoot damped with 42ohm series resistor.
I want to use series resistor with same value.
>What value resistor did you start with??
I start with 33 ohm
>Are you modeling a board with a ground plane or a 2 layer board??
I have 6 layer board include 3 plane(GND, 1.26V, 3.3V).
>mikedunn
Regards
-Zahra
Jeff-
>> I used IBIS model for DSP, SDRAM, flash also series resistor in data bus, and address
bus.
>> Overshoot is on data bus when SDRAM is driver and C6713 is load.
>> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data bus (0-31).
>Mike's questions to you are good ones. Also I would ask where you placed >the series R --
>maybe close to the DSP? If
>so, try placing in the middle of the trace.
first, Series R placed close to the DSP, and had high overshoot.
then I placed series R in middle of the trace but had overshoot.
then I placed series R close to the SDRAM(0.1 inch). with this placement, overshoot limited in D0-15 and D24-31.
>** Please don't cut out text from my reply when you answer. If you do >that, the thread is not
>usable by others in the
>future, and I can no longer help you. **
I dont cut out text from your reply, when i post a fallowup, these deleted automaticly.
>-Jeff
regards
Zahra
>Zahra,
>On 5/19/08, z...@yahoo.com wrote:
>>
>> I used IBIS model for DSP, SDRAM, flash also series resistor in data
>> bus, and address bus.
>> Overshoot is on data bus when SDRAM is driver and C6713 is load.
>> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data bus
>> (0-31).
>>
>What happens if you increase the data bus series resistors 20-25%??
some data bus(D0-15 and D24-31) with 33ohm series resistor damped overshoot.
but in D16-23, overshoot damped with 42ohm series resistor.
I want to use series resistor with same value.
>What value resistor did you start with??
I start with 33 ohm
>Are you modeling a board with a ground plane or a 2 layer board??
I have 6 layer board include 3 plane(GND, 1.26V, 3.3V).
>mikedunn
Regards
-Zahra
Jeff-
>> I used IBIS model for DSP, SDRAM, flash also series resistor in data bus, and address
bus.
>> Overshoot is on data bus when SDRAM is driver and C6713 is load.
>> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data bus (0-31).
>Mike's questions to you are good ones. Also I would ask where you placed >the series R --
>maybe close to the DSP? If
>so, try placing in the middle of the trace.
first, Series R placed close to the DSP, and had high overshoot.
then I placed series R in middle of the trace but had overshoot.
then I placed series R close to the SDRAM(0.1 inch). with this placement, overshoot limited in D0-15 and D24-31.
>** Please don't cut out text from my reply when you answer. If you do >that, the thread is not
>usable by others in the
>future, and I can no longer help you. **
I dont cut out text from your reply, when i post a fallowup, these deleted automaticly.
>-Jeff
regards
Zahra
Reply by ●May 20, 20082008-05-20
Zahra,
On Tue, May 20, 2008 at 2:00 AM, wrote:
> Mikdunn-
>>Zahra,
>
>>On 5/19/08, z...@yahoo.com wrote:
>>>
>>> I used IBIS model for DSP, SDRAM, flash also series resistor in data
>>> bus, and address bus.
>>> Overshoot is on data bus when SDRAM is driver and C6713 is load.
>>> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data
>>> bus
>>> (0-31).
>>>>What happens if you increase the data bus series resistors 20-25%??
>
> some data bus(D0-15 and D24-31) with 33ohm series resistor damped overshoot.
> but in D16-23, overshoot damped with 42ohm series resistor.
> I want to use series resistor with same value.
Don't we all. Did you simulate with all 42 ohm??
What exactly is on your databus??
my guess is...
?? D0-15 = DSP+SDRAM+FLASH
?? D16-23= DSP+SDRAM
?? D24-31=DSP+SDRAM+"something else"
mikedunn
>
>>What value resistor did you start with??
>
> I start with 33 ohm
>>Are you modeling a board with a ground plane or a 2 layer board??
> I have 6 layer board include 3 plane(GND, 1.26V, 3.3V).
>
>>mikedunn
>
> Regards
>
> -Zahra
>
> Jeff-
>
>>> I used IBIS model for DSP, SDRAM, flash also series resistor in data bus,
>>> and address
> bus.
>>> Overshoot is on data bus when SDRAM is driver and C6713 is load.
>>> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data
>>> bus (0-31).
>
>>Mike's questions to you are good ones. Also I would ask where you placed
>> >the series R --
>>maybe close to the DSP? If
>>so, try placing in the middle of the trace.
> first, Series R placed close to the DSP, and had high overshoot.
> then I placed series R in middle of the trace but had overshoot.
> then I placed series R close to the SDRAM(0.1 inch). with this placement,
> overshoot limited in D0-15 and D24-31.
>
>>** Please don't cut out text from my reply when you answer. If you do
>> >that, the thread is not
>>usable by others in the
>>future, and I can no longer help you. **
>
> I dont cut out text from your reply, when i post a fallowup, these deleted
> automaticly.
>
>>-Jeff
> regards
> Zahra
--
www.dsprelated.com/blogs-1/nf/Mike_Dunn.php
On Tue, May 20, 2008 at 2:00 AM, wrote:
> Mikdunn-
>>Zahra,
>
>>On 5/19/08, z...@yahoo.com wrote:
>>>
>>> I used IBIS model for DSP, SDRAM, flash also series resistor in data
>>> bus, and address bus.
>>> Overshoot is on data bus when SDRAM is driver and C6713 is load.
>>> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data
>>> bus
>>> (0-31).
>>>>What happens if you increase the data bus series resistors 20-25%??
>
> some data bus(D0-15 and D24-31) with 33ohm series resistor damped overshoot.
> but in D16-23, overshoot damped with 42ohm series resistor.
> I want to use series resistor with same value.
Don't we all. Did you simulate with all 42 ohm??
What exactly is on your databus??
my guess is...
?? D0-15 = DSP+SDRAM+FLASH
?? D16-23= DSP+SDRAM
?? D24-31=DSP+SDRAM+"something else"
mikedunn
>
>>What value resistor did you start with??
>
> I start with 33 ohm
>>Are you modeling a board with a ground plane or a 2 layer board??
> I have 6 layer board include 3 plane(GND, 1.26V, 3.3V).
>
>>mikedunn
>
> Regards
>
> -Zahra
>
> Jeff-
>
>>> I used IBIS model for DSP, SDRAM, flash also series resistor in data bus,
>>> and address
> bus.
>>> Overshoot is on data bus when SDRAM is driver and C6713 is load.
>>> Maximum overshoot and undershoot on input pins is 4.4V and -1V in data
>>> bus (0-31).
>
>>Mike's questions to you are good ones. Also I would ask where you placed
>> >the series R --
>>maybe close to the DSP? If
>>so, try placing in the middle of the trace.
> first, Series R placed close to the DSP, and had high overshoot.
> then I placed series R in middle of the trace but had overshoot.
> then I placed series R close to the SDRAM(0.1 inch). with this placement,
> overshoot limited in D0-15 and D24-31.
>
>>** Please don't cut out text from my reply when you answer. If you do
>> >that, the thread is not
>>usable by others in the
>>future, and I can no longer help you. **
>
> I dont cut out text from your reply, when i post a fallowup, these deleted
> automaticly.
>
>>-Jeff
> regards
> Zahra
--
www.dsprelated.com/blogs-1/nf/Mike_Dunn.php
