National Semiconductor ADC081C021, Руководство пользователя, Страница: 5 / 21

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The LM4050-4.1 Precision, Micropower, Shunt
Voltage Reference is included on the
ADC121C02XEB as a clean reference solution for
the ADC. To evaluate the ADC using the
LM4050, simply short pins 1 & 2 of JP7, and move
the VA_SELECT jumper to pins 7 & 8 of JP5
(
Figure 5
).
Figure 5: LM4050 Jumper Configuration
3.0 Quick Start
The ADC121C02XEB evaluation board may be
used in the Stand Alone mode to capture data
with a logic analyzer or third party equipment, or it
may be used in the Computer Mode with a
WaveVision 4 Data Capture Board, referenced
throughout the remainder of this document as
WV4. In both cases, the data may be analyzed
with the WaveVision software.
3.1 Stand Alone Mode
Refer to
Figure 1
for locations of test points and
major components.
1. The I
2
C interface signals (SCL and SDA) may
be driven directly at
J1
or with wires soldered
to VIA1 and VIA2 (step 7). A fully-compliant
I
2
C interface analyzer should be used to drive
SCL and SDA while monitoring the data
output (SDA).
2. The board provides the option of adding 2k Ω
pull-up resistors to the I
2
C bus, SCL and SDA.
To enable the pull-up resistors, short pins 1 &
2 of
JP2
. Assuming the I
2
C analyzer has
built-in pull-up resistors, the jumper at
JP2
must be removed to disable the on-board pull-
up resistors. If the I
2
C analyzer doesn’t have
built-in pull-up capability, leave
JP2
shorted.
3. Connect a clean analog (not switching) +5.0V
power source with a 300mA current limit to
power connector
TP7
. Ground
TP6
.
4. Move the shorting jumper at
JP5 to pins 9 &
10.
NOTE: only two consecutive pins may be
shorted on JP5 at a time.
5. Turn on the power supply.
6. Connect the input signal to the test-point at
J2. The input signal return can be connected
to ground at TP3. Please note the evaluation
board is assembled for a DC-coupled input
source. The board is designed for an AC
coupled input as well. Modifying the board for
an AC coupled input is described above in
Section 2.0
. If the source has a 50 ohm output
impedance, install a 51 ohm resistor at R3.
To accurately evaluate the dynamic
performance of the ADC121C021, the source
must be better than 90dB THD.
7. If evaluating the ADC121C027, configure the
I
2
C slave address. The address is controlled
by VIA5. With VIA5 left floating, the slave
address of the ADC121C027 will be set to
50hex. Grounding VIA5 sets the address to
51hex. Connecting VIA5 to V
A
sets the
address to 52hex.
8. If evaluating the ADC121C021, the slave
address is permanently set to 54hex.
9. If evaluating the ADC121C021, the ALERT
pin can be monitored at VIA5.
3.2 Computer Mode
Refer to
Figure 1
for locations of test points and
major components. The board comes configured
for “plug-and-play” WaveVision evaluation.
1. Run the WaveVision 4 program, version 4.4 or
higher is required to interface to the WV4
board. While the program is loading, continue
below.
2. Connect a USB cable between the WV4
board and the PC running the WaveVision 4
software.
3. Make the following required jumper
connections, see
table 1
for more details:
•
JP1
- pins 1 & 2
•
JP2
- pins 1 & 2
•
JP5
- pins 3 & 4 (All other pins of JP5
must be left open)