[SI-LIST] Re: HW Debugging
- From: steve weir <weirsi@xxxxxxxxxx>
- To: olaney@xxxxxxxx
- Date: Fri, 02 Nov 2007 13:47:12 -0700
Orin on probes, the Tek P6150 offers a higher b/w than the 54006A, and
is in some cases easier to use. The 54006A offers 20:1 that the P6150
does not. They both do 10:1, and the P6150 does 1:1 which isn't going
to help looking at DDR but is fine for power delivery.
Best Regards,
Steve.
olaney@xxxxxxxx wrote:
> A 1 GHz o'scope would be fine if you were dealing with 600 MHz sine
> waves, but for digital signals you need enough harmonics to adequately
> represent the rise and fall times, overshoot, ringing, etc. The maximum
> pattern rate will be 300 MHz (10101010...), and the 1 GHz scope will give
> you the third harmonic, which is at least enough to read the bit pattern,
> but a 2 GHz scope will get you (barely) to the 7th harmonic, at which
> point you can start to believe that what you see onscreen represents
> what's happening at the probe tip. Speaking of probes, do not make the
> mistake of matching scope and probe bandwidths -- a 1 GHz probe on a 1
> GHz scope yields a cascaded bandwidth around 707 MHz. A 1 GHz scope with
> a 2 GHz probe gives 894 MHz in cascade, etc. My personal choice is an HP
> 54006A probe that offers a 6 GHz bandwidth. (986 MHz on a 1 GHz scope,
> 1.9 GHz on a 2 GHz scope). The bugaboo of high speed probes is getting
> an adequate ground. That makes you a fan of topside ground planes or
> strategically located bypass caps. If you have the luxury of building in
> coaxial test points that can directly accept 50 ohm cable, life can be
> good - just use a cable instead of a probe. The tiny (and cheap) SMT
> connectors designed for cell phones, for instance, can be sprinkled
> around for debug and production test if you are foresighted enough, and
> pay for themselves in ease of test. The trick is to place a resistor in
> series so that the presence of the probe does not affect normal
> operation, lest you wind up with a circuit that works perfectly only
> while test equipment is attached. The 54006A probe uses a 450 ohm
> resistor for 10:1 voltage division into a 50 ohm scope input. The total
> of 500 ohms at the tip is high enough for probing typical 50 ohm signal
> traces with minimal disturbance. Of course, the resistor has to be
> properly implemented to get good fidelity.
>
> That's all about using a scope, which is often a primitive tool. Others
> on this list can chime in with more advice. I see a few other answers
> have already flowed in.
>
> Orin
>
> On Fri, 2 Nov 2007 13:04:54 +0100 "Santos Fernandez, Jesus"
> <jsantosfernandez@xxxxxxxx> writes:
>
>> Hello all,
>>
>>
>> We are designing a PCB with fastest transmission clock speed of
>> 600MHz.
>>
>> We have 1GHz oscilloscopes (and below)
>>
>>
>>
>> Do you think we will need additional test equipment for any required
>> design testing?
>>
>> If you think so, will you, please, suggest which minimum equipment
>> will
>> be necessary?
>>
>>
>>
>> Thank you in advance,
>>
>> J. Santos
>>
>>
>>
>>
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