DEM-ADS1216 EVALUATION FIXTURE www.ti.com FEATURES DESCRIPTION ● PROVIDES FAST AND EASY PERFORMANCE TESTING FOR ADS1216 ● SEPARATE ANALOG AND DIGITAL POWER ● PC PRINTER PORT CONTROL ● WINDOWS® 95/98 SOFTWARE 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. Windows is a registered trademark of Microsoft Corp. 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. 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/VREF 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 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. FIGURE 1. Time Plot. 2 FIGURE 2. FFT Frequency Plot. 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 = VREF 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. LSB_1st EN_Buff VREF_HI EN_VREF 0 1 Send MSB First No Input Buffer VREF = 1.25V VREF OFF Send LSB First Input Buffer Enabled VREF = 2.5V VREF ON TABLE I. Control Bits. FIGURE 4. Configuration Window. DEM-ADS1216 SBAU038 3 Unipolar/Bipolar The results of the unipolar/bipolar selection are shown in Table II. ANALOG INPUT DIGITAL OUTPUT Bipolar +FSR Zero -FSR 0x7FFFFF 0x000000 0x800000 Unipolar +FSR Zero -FSR 0xFFFFFF 0x000000 0x000000 Calibrate Internal Temp Sensor The Calibrate Temp button opens the Internal Temp Sensor Calibration window for calibration of the internal temperature diode. This allows you to force the temperature readout to match the temperature you enter. This is not intented to give a high-accuracy temperature readout, but will give a reading that is reasonable for a single diode voltage measurement. TABLE II. Unipolar/Bipolar Selection Results. Settling Mode Three Sinc filters can be selected. When the input changes, the fast settling filter settles in one data output interval, Sinc2 settles in two periods, and Sinc3 takes three periods to fully settle. However, the Sinc3 filter has the highest resolution. The desired filter can be selected. Auto mode selects the fast settling filter when the input changes, then it changes to the Sinc2 filter for the second period, and on the third data out period it will use the output of the Sinc3 filter. This gives fast settling when the input channel changes, but the same highresolution results after the necessary number of conversion periods. OK Selecting OK will save the selected setup. FIGURE 6. Temperature Calibration. SET IDACS/PGA/VREF The screen shown in Figure 7 provides the means to observe the interaction of the IDAC settings, REXT and VREF. Additionally, the PGA can be set from this screen. SELECT INPUT CHANNELS Figure 5 gives a graphical method to select the multiplexer channel. This also shows the full flexibility of the ADS1216 multiplexer, which allows any input to be selected as the positive or negative input for a measurement. The mouse selects which switch to close. Additionally, the internal diode can be connected, which turns on the burn out current sources. By measuring the voltage on the diode, a temperature measurement can be made. IDAC1 can also drive this sensing diode. FIGURE 7. PGA Settings. FIGURE 5. Input Multiplexer. 4 DEM-ADS1216 SBAU038 TEST SCREENS Opcode Test. The screen in Figure 8 allows the opcodes to be tested and the results observed. FIGURE 8. Opcode Control. One convenient way to test the communications and operations of the ADS1216 Demo software is to go to this screen, select “Reset”, and then “Read all Regs”. You should end up with a register dump that looks like Figure 9. FIGURE 10. Ram Test. Noise Test This test provides an automated means to verify the performance of the ADS1216 across various decimation ratio values, PGA settings and with averaging of the results. With all the options selected, this test can take a long time to complete. The results are displayed in a tabular format, which shows the PGA settings, Decimation Rate, Average Output, Standard Decmiation, and Effective number of bits, as shown in Figure 11. FIGURE 9. Reset Condition. You can observe that the reset state of the registers are: F6, 10, 00, 00, 00, 00, 00, FF, F0, 00, 00, 00, 00, 22, 90, 67. This screen also shows the state of the digital control signals. Any opcode can be entered and tested to observe the results RAM R/W Test The test screen in Figure 10 provides tools for testing RAM. Various simple operations have been assigned to a button. Additionally, a full RAM test can be executed with the “Test Ram” button. This clears RAM, generates random data, writes to the RAM and verifies that the contents matches the random data. FIGURE 11. Noise Test Results. The “File” menu selection gives you the option to save your data. All data is saved in a comma delimited format so that it can be imported into a spreadsheet for further analysis. DEM-ADS1216 SBAU038 5 FIGURE 12. Schematic. 6 DEM-ADS1216 SBAU038 TOP (TRACES AND GND PLANE) FIGURE 13. Top Layer. BOTTOM (TRACES AND GND PLANE) FIGURE 14. Bottom Layer. DEM-ADS1216 SBAU038 7 COMPONENT LIST PART NUMBER DESCRIPTION REF. DES. QTY VENDOR PART NUMBER MANUFACTURER ADS1216 20-BIT A/D Converter U1 1 ADS1216 Burr-Brown CK05BX104K CAP, 0.10µF, 50V, 10%, CERAMIC X7R C0-1,C2-3,C4-5,C6-7 4 CK05BX104K KEMET CK05BX470K CAP, 47pF, 200V, 10%, CERAMIC X7R C0,C1,C2,C3,C4,C5 9 CK05BX470K KEMET * C6,C7,CC1 CRCW12061001F RES, 1.0KΩ, 0.125W, 1%, CHIP-THICK-FILM R10 1 CRCW12061001F DALE CRCW12062000F RES, 200Ω, 0.125W, 1%, CHIP-THICK-FILM R12,R13,R14,R15,R16 13 CRCW12062000F DALE * R21,R22,R23,R24,R25 * R26,R27,R28 C1206C100K1GAC CAP, 10pF, 100V, 10%, CHIP-CERAMIC COG C28 1 C1206C100K1GAC KEMET C1206C104K5RAC CAP, 0.10µF, 50V, 10%, CHIP-CERAMIC X7R C14,C15,C16,C20,C22 9 C1206C104K5RAC KEMET C1206C220K1GAC CAP, 22pF, 100V, 10%, CHIP-CERAMIC COG C18,C19 2 C1206C220K1GAC KEMET ED 120/10 OST 10-Pin TERM BLK;0.2 OC P1 1 ED 120/10 ED 300/2 C23,C25,C26,C27 8 ED 300/2 2 PIN TERMINAL BLK; 5MM PITCH P2,P3 2 HC49 2.4576MHz CRYSTAL;CTS;Cell HC18U Y1 1 HC49 P6KE6.8A ZENER 6.8V D1,D2 2 P6KE6.8A REG1117-5 +5V Regulator Q1 1 REG1117-5 Burr-Brown RN55C49R9F RES, 49.9Ω, 0.125W, 1%, METAL-FILM R0,R1,R2,R3,R4,R5 9 RN55C49R9F DALE * R6,R7,RC1 RN55C1000F RES, 100Ω 0.125W, 1%, METAL-FILM R11 1 RN55C1000F DALE TSW-1-S01-06-S 1-Pin TERMINAL; CELL TP042 T3,T4,T5,T6,T7,T8 28 TSW-1-S01-06-S * T9,T10,T15,T16,T17 * T18,T19,T20,T21,T22 * T24,T25,T26,T27,T28 * T29,T30,T31,T32,T33 * T34,T35 TSW-102-07-L-S CONN, 2 POS .1 CTR .025 SQ. POST T1,T2,T36,T37 4 TSW-102-07-L-S T491B105K350AS CAP, 1µF, 35V, 10%, TANTALUM CHIP-MOLDED C17 1 T491B105K035AS KEMET T491D106K035AS CAP, 10µF, 35V, 10%, TANTALUM CHIP-MOLDED C21,C24 2 T491D106K035AS KEMET 74hct04d IC, Inverter, hex U3 1 74hct04d 74hct74d IC, Flip Flop, Dual J-K with clear & preset U4 1 74hct74d 74hct245dw IC, Bus Transceiver, Octal, 3-state outputs U2 1 74hct245dw 747842-6 25 Pin Right Angle Male D Conn P4 1 747842-6 DEM-ADS1216 SBAU038 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. 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