EVAL-AD7891-1CB Datasheet, PDF (8/12 Pages) Analog Devices – Evaluation Board for Single Supply, 12-Bit 454 kSPS ADC

EVAL-AD7891-1CB
Digital Storage Oscilliscope.
When samples of data are captured, they are displayed on the
Digital Storage Oscilliscope. If the blackman-harris button is
turned on then the windowed data is also displayed on the
oscilliscope. The 'scope has been designed to act in a similar
way as a conventional oscilliscope. To the right of the
oscilliscope are several buttons that control the manner in which
data is displayed on the 'scope. The timebase for the
oscilliscope is automatically chosen by the software if the Time/
Div "Auto" button is on. The user can also select the timebase
by clicking in the Time/Div window and scrolling up and down
through the possible timebases. Similarly, the vertical scale of
the oscilliscope is chosen automatically if the Volt/Div "Auto"
button is on. The user also has the option of selecting the
desired vertical scale in a similar manner to selecting the
timebase.
The other buttons associated with the oscilliscope are:
grid This button toggles the grid display of the oscilliscope
on and off.
axis This button toggles the axis display of the oscilliscope
on and off
text This button toggles the text displayed on the
oscilliscope screen on and off.
line When the line button is on, the displayed samples are
joined together by lines. When this button is off, the
samples are displayed as points.
ac
When this button is on, the dc component of the
sampled signal is removed and the signal is displayed.
This has the effect of centering the signal vertically on
the oscilliscope screen. When this button is on, the dc
component is not removed and the signal is displayed
with its horizontal axis corresponding to a code of 0.
The ac display option is useful for zooming in on a
low-level signal that has a large dc offset.
dual When the "dual" button is on, the oscilliscope screen is
divided into two parts with the sampled data display
centered on one horizontal axis and the windowed data
display centered on another. When the "dual" button
is off, both traces are centered on the same horizontal
axis.
1
This button toggles the sampled data trace on and off
2
This button toggles the windowed data trace on and
off.
Histogram Analyzer
The histogram analyzer counts the number of occurrences of
each code in the captured samples and displays a histogram of
these counts. The most frequently occurring code is displayed
in the center of the histogram. The analyzer is normally used
with a dc input signal and calculates the mean and the standard
deviation of the sampled data. The mean and standard devia-
tion are displayed in both volts and in units of the lsb size of the
converter. The histogram gives a good indication of the dc
noise performance of the ADC. The standard deviation shows
directly the noise introduced in the conversion process.
–8–
REV. A