[SI-LIST] Re: Measuring Power supply noise

  • From: Zhangkun <zhang_kun@xxxxxxxxxx>
  • To: BalaKrishnan.Kesavaperumal@xxxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
  • Date: Mon, 20 Mar 2006 21:16:37 +0800

Dear Bala

I suggest that the 1M ohm should not be used because of resonance. In our 
measurement, there is the following setting

    <20MHz          1M ohm could be used for the frequency is too low for 
resonance.
    full bandwidth  50 ohm should be applied to avoid resonance.

Hope this is helpful.

Best Regards

Zhangkun
2006.3.20
----- Original Message ----- 
From: "BalaKrishnan, Kesavaperumal (IE10)" 
<BalaKrishnan.Kesavaperumal@xxxxxxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Monday, March 20, 2006 8:53 PM
Subject: [SI-LIST] Measuring Power supply noise


> Hi,
>  
> 
> To measure the noise of the power plane (We use LDO to generate 5V), 
> 
>  
> 
> I did the following
> 
> a) I built a cable using a 50?Coax cable and used the internal termination of 
> the oscilloscope.
> 
> b) Removed a CAP from the board, used these PADS to solder my probe.
> 
>  
> 
> The noise measured was around 20mV
> 
>  
> 
> To check the sanity of my measurement, Instead of my 50?probe, I used a 
> standard 1M?probe and carried out the measurement.
> 
> The measured noise was around 50mV
> 
>  
> 
> I have the following question.
> 
>  
> 
> a)       By using a 50?probe, did I create a voltage divider?
> 
>  
> 
> Thanks in advance for your time.
> 
>  
> 
> Regards,
> 
> Bala
> 
>  
> 
> 
> ------------------------------------------------------------------
> 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 FAQ wiki page is located at:
>                 http://si-list.org/wiki/wiki.pl?Si-List_FAQ
> 
> List technical documents are available at:
>                 http://www.si-list.org
> 
> List archives are viewable at:     
> //www.freelists.org/archives/si-list
> or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
> 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 FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: