EVAL-AD7891-2CB Datasheet, PDF (10/12 Pages) Analog Devices – Evaluation Board for Single Supply, 12-Bit 500 kSPS ADC

EVAL-AD7891-2CB
fundamental frequency. The counter is increased by clicking on
the SigBins "+" button and decreased by pressing on the SigBins
"-" button. As the counter is changed, the SNR is re-calculated
and displayed. For a blackman-harris window, the power in the
central peak plus the power in four bins each side of the central
peak is normally used for SNR calculations. In a coherent
sampled data system, all the power from the sine wave is
contained in one frequency bin. In such a case the SigBins
counter shoud be set to zero.
The number of low frequency bins that are replaced by average
noise in the SNR calculation, is controlled by the DcBins
counter. The range of valid values is 0 to 9. The counter is
increased by clicking on the DcBins "+" button and decreased
by pressing on the DcBins "-" button. As the counter is
changed, the SNR is re-calculated and displayed. For a
blackman-harris window, the first three to five bins are normally
replaced by average noise in the SNR calculation. In a coherent
sampled data system, all the dc power is contained in the first
frequency bin. In such a case the SigBins counter shoud be set
to one.
APPENDIX A: CONFIGURATION FILE DESCRIPTION
There are two configuration files on the distribution disk that
comes with the AD7891-2 evaluation board. They are
AD7891IN.CFG, which is used when the EVAL-CONTROL
BOARD provides the CONVST signal, and AD7891EX.CFG,
which is used when an externally provided CONVST signal is
used. They provide initial configuration information to the
AD7891-2.EXE program. Normally no changes need to be
made to the .CFG files. However sometimes it may be desired
to change the initial configuration. This is done by editing the
file to make the changes and then saving the changes before
running the AD7891-2.EXE program. Here is a listing of the
contents of the AD7891IN.CFG file.
[DemoController]
Use69=FALSE
AFlags=TRUE
Sports=FALSE
Voltage=5
There are three main sections to the configuration file. The
name of each section is given in square brackets in the file
listing. These sections are [DemoController], [EvalBoard] and
[AnalogInput]. Comments are included in the listing by
preceeding the comment with a semi-colon.
[DemoController] section
This section controls some of the settings of the EVAL-
CONTROL BOARD card. These settings should not be
changed.
[EvalBoard] section
This section tells the AD7891-2.EXE program the name of the
part being evaluated, the .HIP program that needs to be
downloaded to the ADSP-2111, the number of bits of the ADC,
the maximum sampling frequency, the default sampling
frequency, the default number of samples to be taken and the
form of coding used by the ADC.
The sampling frequencies are in Hertz. There are three valid
types of binary coding. These are TwosComplement, Binary
and OffsetBinary. Binary and OffsetBinary are interpreted in
the same manner in the AD7891-2.EXE program and may be
used interchangeably.
[AnalogInput] section
InputRange gives the default voltage range of the input channel.
Valid values for InputRange for the AD7891-2 are 5V (for the
± 2.5V and 0 to 5V ranges) and 2.5 V (for the 0 to 2.5V range).
InputOffset is the input voltage that returns a code of zero from
the AD7891-2.
[EvalBoard]
Part=AD7891-2
Program=ad7891in.hip
NumBits=12
MaxFrequency=600000
DefaultFrequency=200000
DefaultNsamp=256
BinaryCoding=TwosComplement
;BinaryCoding=Binary
;BinaryCoding=DffsetBinary
[AnalogInput]
InputRange=10
InputOffset=0
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