http://www.national.com
3
1.0 Introduction
This Design Kit (consisting of the ADC Evaluation
Board and this User's Guide) is designed to ease
evaluation and design-in of National
Semiconductor’s ADC121C021 family of Analog-
to-Digital Converters. The ADCs can operate at
speeds up to 188.9 kSPS. The converter features
an I
2
C interface and an Alert function. This User’s
Guide supports all three resolutions and both
package options of the ADC121C021 ADC family.
All the devices in the family (ADC121C021,
ADC121C027, ADC101C021, ADC101C027,
ADC081C021, and ADC081C027) will be referred
to as the ADC121C021 in this document. The
ADCXX1C021 options offer an ALERT output pin,
whereas, the ADCXX1C027 offers an address
selection pin. The board comes stuffed with the
ALERT option (ADCXX1C021). To evaluate the
Address Option (ADCXX1C027) with this board,
please go to
www.national.com
and order
samples. Use care when de-soldering the ADC to
ensure the pads of U3 are not damaged.
The evaluation board can be used in either of two
modes. In Stand Alone, suitable test equipment
such as a logic analyzer with a pattern generator
can be used with the board to evaluate the
ADC121C021’s performance.
In the Computer mode, data capture and
evaluation are simplified by connecting the
evaluation board to National Semiconductor's
WaveVision 4 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. WaveVision
also provides control of the ADC’s internal
registers through the WaveVision4 software.
The signal at analog input J2 is digitized by U3,
the ADC121C021.
Figure 1: Component Locations
JP1: INPUT
SELECT
JP5: VA
SELECT
J2: INPUT
JP2: I
2
C PULL-UP
Enable
J1: WV4S
Connector
JP7: 4.1V
REF Enable
U3: ADC
[ADC121C021]
U5: REF
[LM4050-4.1]
U2: AMP
[LMP7731]
