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dc2071afc
DEMO MANUAL DC2071A
To change the default settings for the LTC2373-18 se-
quencer in PScope, click on the Set Demo Bd Options
button in the PScope tool bar shown in Figure 8. This will
open the Configure Sequencer menu of Figure 9. In this
menu it is possible to set the number of sequences up to
16, the channel configuration, format and gain compres-
sion setting for each sequence. There is also a button to
return PScope to the default DC2071 settings which are
optimized for the default hardware settings of the DC2071A.
There are a number of scenarios that can produce mislead-
ing results when evaluating an ADC. One that is common
is feeding the converter with an input frequency that is
a sub-multiple of the sample rate and which will only
exercise a small subset of the possible output codes.
The proper method is to pick an M/N frequency for the
input sine wave frequency. N is the number of samples
in the FFT. M is a prime number between one and N/2.
Multiply M/N by the sample rate to obtain the input sine
wave frequency. Another scenario that can yield poor
results is if you do not have a signal generator capable of
ppm frequency accuracy or if it cannot be locked to the
clock frequency. You can use an FFT with windowing to
reduce the leakage, or spreading of the fundamental, to
get a close approximation of the ADC performance. If an
amplifier or clock source with poor phase noise is used,
the windowing will not improve the SNR.
Figure 8. PScope Tool Bar
DC2071A SETUP
Figure 9. PScope Configure Sequencer Menu
