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3
1.0 Introduction
The ADC122S655EB/RoHS Design Kit (consisting
of the ADC122S655 Evaluation Board and this
User's Guide) is designed to ease evaluation and
design-in of the National Semiconductor
ADC122S655 12-bit Analog-to-Digital Converter.
This ADC has two analog input channels that are
sampled simultaneously and can operate at
speeds up to 500 kSPS. The converter’s digital
outputs are available on single or dual data ouput
pins.
The evaluation board can be used in either of two
modes. In Stand Alone, suitable test equipment
such as a logic analyzer can be used with the
board to evaluate the ADC122S655’s
performance.
In the Computer mode, data capture and
evaluation is simplified by connecting the
evaluation board to National Semiconductor's
Data Capture Board (order number WAVEVSN
BRD 4.1 or higher) which connects to a personal
computer through a USB port and runs
WaveVision 4 software revision 4.4 or higher.
The latest version of the WaveVision 4 software
should be downloaded from the web at
http://www.national.com/adc
.
Note: WaveVision software version 4.4 or higher
is required to evaluate this part with the WV4
Evaluation System.
The WaveVision 4 software operates under
Microsoft Windows. The signal at the analog
input is digitized, captured, and displayed on a PC
monitor in the time and frequency domains.
The software will perform an FFT on the captured
data upon command. This FFT plot shows the
dynamic performance in the form of SNR, SINAD,
THD, SFDR, and ENOB. A software histogram of
the captured data is also available.
The signals at analog input J3 are digitized by U5,
the ADC122S655. The ADC122S655 either uses
a crystal oscillator (Y2) which is provided on this
board or an externally supplied clock at TP15.
Figure 1 Component and Test Point Locations
JP8: VREF
J1: INPUT
JP12: CLK
JP11: VA
