TEXAS INSTRUMENTS DEM-ADS1216 Technical data
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DEM-ADS1216
EVALUATION FIXTURE
FEATURES
● PROVIDES FAST AND EASY
PERFORMANCE TESTING FOR ADS1216
● SEPARATE ANALOG AND DIGITAL
POWER
● PC PRINTER PORT CONTROL
● WINDOWS® 95/98 SOFTWARE
Windows is a registered trademark of Microsoft Corp.
DESCRIPTION
The DEM-ADS1216 demo board is designed for ease
of use when evaluating the ADS1216 high resolution
analog-to-digital converter. The ADS1216 offers
24-bits no missing codes performance. It has 8 input
channels that can be configured as up to 8 differential
channels. The multiplexer is followed by a programmable gain amplifier with selectable gains of up to
128.
Hardware options include user defined clock frequency,
internal or external reference, and input biasing.
All of the features and functionality of the ADS1216
can be exercised using the pull-down menus available
from the DEM-ADS1216 software.
Copyright © 2001, Texas Instruments Incorporated SBAU038 Printed in U.S.A. February, 2001
INITIAL CONFIGURATION
WINDOWS SOFTWARE
The DEM-ADS1216 is designed to be operational without any
user configuration except connecting the power supplies and the
communications cable to the PC printer port. To use the internal
reference voltage, jumpers T1 and T2 should be installed.
POWER SUPPLY
The analog and digital supplies should be connected together at the power supply. That means that a pair of wires
should go from VCC and AGND to the power supply and a
separate pair of wires should go from VDD and DGND to the
same +5Vpower supply.
VOLTAGE REFERENCE
With jumpers T1 and T2 installed the DEM-ADS1216 Demo
Board will use the internal reference. These jumpers can be
replaced and connections made to the pins, to use an external
reference.
CLOCK
A 2.4576MHz crystal is connected to the XIN and XOUT
pins to provide a convienient frequency for 60Hz rejection.
PC BOARD LAYOUT
The DEM-ADS1216 demo board consists of a 2-layer PC
board. To achieve the highest level of performance, surfacemount components are used wherever possible. This reduces
the trace length and minimizes the effects of parasitic capacitance and inductance. The demo board has a divided ground
with all the analog signals over one portion and the digital
signals in the other. Keep in mind that this approach may not
necessarily yield optimum performance results when designing the ADS1216 into different individual applications. In any
case, thoroughly bypassing the power supply and reference
pins of the converter is strongly recommended.
The breadboard area is provided so that input filters can be
added. As shipped, the board includes an R-C filter (49.9Ω
and 47pF) on each input with 0.1µF differential capacitor
between adjacent channels.
The ADS1216 uses registers and a 1-byte opcode to control
the operation. The evaluation software provides a convenient method to issue the commands and receive the results.
It also can display the results of acquired data, as shown in
Figure 1, and perform a frequency analysis, as shown in
Figure 2.
The program is organized with pull-down menus as follows:
File
Display Data List
Save Data
Save FFT Data
Print Data
Exit
Configuration
Configure Digital Filter
Select Input Channel
Set IDACs/PGA/V
Tests
Opcode Test
RAM R/W Test
Noise Test
Options
Data List Format
Voltage
Raw Hex
Raw Decimal
Set FFT Window
Rectangular
Hamming
Blackman
Blackman Harris
Continuous 5th Derivative
FFT Harmonic Bins
Number of Harmonic Bins
Number of DC Bins
Help
About ADS1216 Demo SW
REF
FIGURE 1. Time Plot. FIGURE 2. FFT Frequency Plot.
2
DEM-ADS1216
SBAU038
SAVE DATA
The Save Data List shown in Figure 3 displays the individual
data values as well as the mean and standard decimation of
the data.
FIGURE 3. Data List.
CONFIGURATION
The Configure Digital Filter opens a window that provides
many options, as shown in Figure 4.
Filter Decimation Ratio
The Filter Decimation Ratio box allows you to adjust the
decimation ratio with the scroll bar or by entering the value
in the box at the bottom. Additionally, as you change the
decimation ratio, you can observe the resulting data rate.
Calibration Registers
The current values of the Offset, Full-Scale Output Data
registers can be read and displayed. Additionally, these
values can be changed by entering a new HEX value in the
field and pushing the set button.
Calibration
Five types of calibration can be performed. When the button
is pushed the ADS1216 performs the calibration then it
reads back and displays the results in the calibration registers. The five types of calibration are:
1) Selfcal—Both Offset and Gain Calibration
2) Selfocal—Only Offset Calibration
3) Selfgcal—Only Gain Calibration
4) Sysocal—Offset Calibration, Input = 0V
5) Sysgcal—Gain Calibration, Input = V
REF
Set I/O Direction
The eight pins of I/O can be individually set for output or
input. The output pins will be set to the HEX value entered
in the “Write I/O” field when the “Write I/O” button is
selected. The value of all pins will be displayed in the box
next to the “Read I/O” button when it is selected.
Status
The various control bits can be set and monitored in the
status box. Additionally, the revision ID of the ADS1216
will be displayed. The status bits and their functions are
shown in Table I.
01
st
LSB_1
EN_Buff No Input Buffer Input Buffer Enabled
V
_HI V
REF
EN_V
REF
Send MSB First Send LSB First
= 1.25V V
REF
V
OFF V
REF
REF
REF
= 2.5V
ON
TABLE I. Control Bits.
FIGURE 4. Configuration Window.
DEM-ADS1216
SBAU038
3
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