[SI-LIST] Re: VOH(AC) vs VOH(DC) DDR3 measurements
- From: Hermann Ruckerbauer <Hermann.Ruckerbauer@xxxxxxxxxxxxx>
- To: mik.nazaryan@xxxxxxxxx
- Date: Tue, 13 Nov 2012 07:50:45 +0100
Hello,
I have not checked the procedure in detail, because I don't think it
makes really sense do do the measurement in the System (I communicated
this already to Agilent ... )
Table 30 of 79-3E spec:
Voh(DC) is given for the IV curve linearity measurement
Voh(AC) is given for AC slew rate measurements when driving into an
effective test load of 25Ohm against VTT
Of course you can measure this values in a Read burst in the system
(when probing at the controller side), but this are device output
parameter and nothing one want to measure in the System.
What you would need to do is to get the input parameters of your
controller and measure Vih/Vil of your controller spec for Reads at the
controller side ...
One would need to generate 3 sets of measurement in the compliance test:
- System Write parameters for measurement at the DRAM
- System Read parameters for measurements at the Controller
- Device output parameters test for measurement of device parameters on
a special test load board.
My target was to prepare this three setups with the next compliance test
I'm doing. If anybody is interested in this three setups just contact me
directly ...
Hermann
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schrieb Mik Nazaryan:
> Hi All,
> Currently I have a project with DDR3 running at 800 MHz, and my automatic
> test equipment&software sometimes surprises me with bugs :). So I decided to
> do some measurements manually.
> I read the "measurement algorithm" for VOH (AC) and VOH (DC) from Agilent
> DDR3 Compliance Test instructions.
> Measurement algorithm VOH (AC) and VOH (DC) are the same ! ? Can't find any
> difference !!!
> Thus, the question arises. If the measurements algorithms are the same
> , sowhy the
> specification is different?
> Here is Measurement Algorithm for DC and AC as well.
> Measurement Algorithm
> 1 Acquire and split read and write burst of the acquired signal.
> 2 Take the first valid READ burst found.
> 3 Find all valid positive pulses. A valid positive pulse starts at VREF
> crossing at valid rising edge and ends at VREF crossing at the following
> valid falling edge.
> 4 Zoom in on the first valid positive pulse and perform VTOP measurement.
> Take the VTOP measurement result as VOH(AC) value.
> 5 Continue the previous step with the rest of the valid positive pulses
> that were found in the burst.
> 6 Determine the worst result from the set of VOH(AC) measured.
>
> Thanks.
>
>
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