[SI-LIST] Re: Measuring Power supply Ripple and Noise
- From: David Instone <dave.instone@xxxxxxxxxx>
- To: DAVID CUTHBERT <telegrapher9@xxxxxxxxx>
- Date: Fri, 14 Nov 2008 09:37:59 +0000
A 450 ohm surface mount resistor tombstoned of the 'hot' point in
series with the coax gives a 10:1 probe which only loads the PSU with
500 ohms and reduces the dissipation in the scopes 50 ohm load There
will be some frequency response effects - which can be very small.
Other values can of course be used if you don't have 450 to hand.
My probe of preference is always an active differential probe, providing
it has the bandwidth and can take the voltage.
Regards
Dave Instone
+44 (0)1235 824963
OXFORD SEMICONDUCTOR LIMITED
25 MILTON PARK
ABINGDON
OXFORDSHIRE
OX14 4SH
Registered in England no 2733820
Registered Address: As above
DAVID CUTHBERT wrote:
> Jaiso,
> soldering a coaxial cable directly to the board works very well. The
> common-mode noise rejection is good. Set the 'scope to 50 ohms.
>
> Power supply boards commonly have CM noise on them and this is a real
> problem with single-ended X10 probes. An active differential probe can work
> well.
>
> Dave Cuthbert
>
> On Wed, Nov 12, 2008 at 11:46 PM, Jaison Fernandez
> <jaisonf@xxxxxxxxxxxxxxx>wrote:
>
>
>> Hai all,
>> I am trying to characterize the power integrity of of a board (that having
>> a
>> system clock running at 400Mhz and DDR memory)
>> What is the type of probe (Single ended or differential) is best suited for
>> measuring power supply ripple and noise in the board.(I am using Tek GHz
>> Oscilloscope for this purpose)
>> Can any one give any document regarding measuring power integrity of a
>> board.
>>
>>
>>
>>
>> With Warm Regards,
>>
>> JAISON FERNANDEZ
>>
>>
>>
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