[SI-LIST] Re: Measuring Power supply Ripple and Noise
- From: steve weir <weirsi@xxxxxxxxxx>
- To: David Instone <dave.instone@xxxxxxxxxx>
- Date: Fri, 14 Nov 2008 05:11:04 -0800
Both TEK and Agilent offer 10:1 passive probes. I far prefer to use
these probes when possible rather than soldering up coax. The TEK
probes come with 1:1 50 Ohm, and 10:1 500 Ohm probe tips. The Agilent
come with 10:1 500 Ohm, and 20:1 1000 Ohm tips. I find myself using the
TEK 1:1 probes most often. The other took in the kit are 5kHz 50Ohm DC
blocks available from Sun Moon Electronics.
Steve
David Instone wrote:
> 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
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> 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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Steve Weir
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