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From: John Devereux
Subject: Re: Help: Why 1.5V output in Samsung SRAM K6R1016C1C(KM6161002C) ?
Date: Fri, 27 Dec 2002 22:31:45 +0000
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NNTP-Posting-Date: 27 Dec 2002 22:31:18 GMT
"Zhong Pan" wrote:
>"John Devereux" wrote in message
>> If you've switched the scope to 50 ohms it will be a big
>> load! So don't do that :)
>I guess I AM using 50 ohms! All our coaxial cables are 50 ohms with SMA
>We are just using a home-made probe connecting to the cable. The reason is
>that we need
>to measure from several Mb/s to 10Gb/s digital signal using the DCA. Do you
>we can buy the right probe which can be connected to SMA?
>In terms of the DCA itself, I am not sure if it is 50 ohms terminated. But I
>we did have problem measuring ECL signals 'cause ECL is current output
>instead of voltage.
I would just use a normal scope to diagnose any RAM problem,
until you work out what is going on... If you can't tell how
this "DCA" thing is terminated it's more trouble than it's
worth right now. (If the DCA can measure dc voltages, you
should be able to measure the termination resistance using
a multimeter on ohms applied to the probe tip and earth
Can you solder a 470 ohm resistor in series with the "probe"
tip? This will effectively be a ~10:1 probe with an
impedance high enough for most digital signals. If your 5V
supply now only measures 0.5V, you know the termination is
Use a chip resistor or carbon composition (non-inductive)
for high frequencies.
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