Suresh, as Cosmin pointed out, in the audio frequency range differential routing and keeping the two lines of the pair close together is done to minimize the impact of noise from internal (e.g. power supply) and external (e.g. EM radiation) sources. Depending on your system, even noise sources in the frequency range beyond audio can have an audible impact - e.g. if you have a ADC with sufficient input bandwidth (not sample rate) in your path to digitize the signal, the noise may get aliased into the audio band (think Nyquist). On the other hand, given your low frequency limit of the audio range, path impedance matching is not a concern at all - this becomes important only if your path length approaches ~1/10th of your shortest wave length: 1 GHz --> lambda ~ 15cm (stripline in FR-4) --> limit ~ 1.5cm 1 MHz --> lambda ~ 150m (stripline in FR-4) --> limit ~ 15m 100 kHz --> lambda ~ 1500m (stripline in FR-4) --> limit ~ 150m (this is your case) Wolfgang Cosmin Iorga <ci249534@xxxxxxxxx> Sent by: si-list-bounce@xxxxxxxxxxxxx 11/25/2009 08:44 AM To Suresh V <vsuresh@xxxxxxxxxxxxxxxxxxxx>, si-list@xxxxxxxxxxxxx cc Subject [SI-LIST] Re: Analog Audio Frequancy range Differential Signal Routing constriants Suresh, The main purpose of using differential routing in your uV signal low frequency application is to reduce the coupled noise: crosstalk, ground bounce, and inductive and capacitive coupling as common mode cancellation on both lines, so you need to identify/analyze the specific noise sources and the coupling paths in your application when routing these signals. Let me know offline if you need more details. Cosmin Iorga, NoiseCoupling.com http://www.noisecoupling.com ________________________________ From: Suresh V <vsuresh@xxxxxxxxxxxxxxxxxxxx> To: si-list@xxxxxxxxxxxxx Sent: Wednesday, November 25, 2009 2:06:56 AM Subject: [SI-LIST] Analog Audio Frequancy range Differential Signal Routing constriants Hi experts, In our Project, we have multi-channels hydrophone Sensor interface (µV signal level in Audio Frequency range) which are differential type signals, since these are low frequency Analog type signal is differential Routing constraints & TL impedance Matching is required?? These sensor signals are input to Pre-Amplifier and I am finding difficulties to maintain differential routing. Please let me know if any other critical SI Constraints/guidelines for Sensor Analog differential Signals Thanks in advance Regards, Suresh,v Please do not print this email unless it is absolutely necessary. Spread environmental awareness. -------------------------------------------------------DISCLAIMER------------------------------------------------------ The information transmitted herewith is confidential and proprietary information intended only for use by the individual or entity to which it is addressed. If the reader of this message is not the intended recipient, you are hereby notified that any review, retransmission, dissemination, distribution, copying or other use of, or taking of any action in reliance upon this information is strictly prohibited. If you have received this communication in error, please contact the sender and delete the material from your computer. --------------------------------------------------------------------------------------------------------------------------- ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net 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 technical documents are available at: http://www.si-list.net 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 technical documents are available at: http://www.si-list.net 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