[SI-LIST] Re: Help! SDA suffered crosstalk from SCL, Fall time increased!
- From: Tayyab Rahimkhan Pathan <Tayyab_Pathan@xxxxxxxxxxx>
- To: "imerxu@xxxxxxxxx" <imerxu@xxxxxxxxx>
- Date: Thu, 13 Sep 2012 14:02:13 +0000
Are you using any noise bypass cap on SDA/SCL like 33pF or so?
Can you elaborate the I2C bus design with CLK Freq, number of slave devices and
bus length details?
Regards,
Tayyab
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Rohit MISHRA
Sent: Thursday, September 13, 2012 6:24 PM
To: imerxu@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Help! SDA suffered crosstalk from SCL, Fall time
increased!
Hello Alvis,
There is no waveforms attached with your mail as attachment is prohibited in
si-list.
You rightly pointed out that rise/fall time depends on capacitance of line but
question is what is the total capacitance SDA line will see ?
Actually capacitance seen by SDA line is the sum of capacitance between SDA
line and ground(C1) & capacitance between SDA and SCL line(C2) and I hope you
know that when you talk about crosstalk between SDA & SCL, it's the C2 that is
the culprit for the crosstalk ( Here I assume inductive crosstalk is negligible
!)
Now when SDA and SCL lines are at same potential, SDA line will see less
capacitance (C1) (As both plates of C2 have same potential so can't be charged
!) that means fast rise/fall time but when SDA and SCL are at different
potential, SDA line will have to charge both C1 and C2 that means more
capacitance and hence more rise/fall time.
Hope that helps.
Rgds,
Rohit Mishra
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Imer Xu
Sent: Thursday, September 13, 2012 5:20 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Help! SDA suffered crosstalk from SCL, Fall time increased!
Hi all,
Here's the situation I'm facing: SDA and SCL of the same I2C device are
crosstalking with each other. But what I'm confused is that if crosstalk
happens near the fall edge of SDA, the falling will be slower, hence the fall
time will increase(from 8ns of normal to 88ns)! From my point of view, every
time SDA falls to "0", no matter when falling edge of SCL happens, we are
discharging the same capacitor(parasitic) via the same resistor (in other way,
we are driving the same MOSFET of the open drain circuit of the I2C bus), the
slew rate or fall time of the SDA falling edge should be the same. Please help
with this problem: how could crosstalk affect fall time?
You could refer to the attached waveforms I captured.
I'm a newbie for SI, many thanks to your attention and help :)
Best Regards
Alvis Xu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
**************** CAUTION - Disclaimer *****************
This e-mail contains PRIVILEGED AND CONFIDENTIAL INFORMATION intended solely
for the use of the addressee(s). If you are not the intended recipient, please
notify the sender by e-mail and delete the original message. Further, you are
not
to copy, disclose, or distribute this e-mail or its contents to any other
person and
any such actions are unlawful. This e-mail may contain viruses. Infosys has
taken
every reasonable precaution to minimize this risk, but is not liable for any
damage
you may sustain as a result of any virus in this e-mail. You should carry out
your
own virus checks before opening the e-mail or attachment. Infosys reserves the
right to monitor and review the content of all messages sent to or from this
e-mail
address. Messages sent to or from this e-mail address may be stored on the
Infosys e-mail system.
***INFOSYS******** End of Disclaimer ********INFOSYS***
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
