User's Guide SBAU147 – March 2009 ADS1672EVM and ADS1672EVM-PDK User's Guide ADS1672EVM (Left) and ADS1672EVM-PDK (Right) This user's guide describes the characteristics, operation, and use of the ADS1672EVM, both by itself and as part of the ADS1672EVM-PDK. This evaluation module (EVM) is an evaluation platform for the ADS1672, a high-speed, single-channel, 24-bit, 625kHz delta-sigma analog-to-digital converter (ADC).
www.ti.com space 1 2 3 4 5 6 7 8 9 10 11 12 13 Contents EVM Overview ............................................................................................................... 3 Introduction ................................................................................................................... 3 Analog Interface.............................................................................................................. 3 Reference Buffer .................................................
EVM Overview www.ti.
Analog Interface www.ti.com Analog input signals to the THS4520/ADS1672 signal chain can be applied at connectors J1 (inverting input, –IN) and J2 (noninverting input, +IN) or P3-1 (–IN) and P3-2 (+IN). The P3 connector is an SMT plug on the top side of the PCB (as Figure 1 shows). The signal at +IN and –IN should be differential and centered at 2.5V. Figure 1.
Analog Interface www.ti.com Following the THS4520, an R-C network connects directly to the ADS1672. This R-C network (R56, R15, C18, R55, and R14) acts as a first-order, anti-aliasing filter for the ADS1672. The corner frequency of the installed first-order filter is 1/[2π × (10Ω + 10Ω) × 750pF] or 10.6MHz. Pads are available to install more resistors and capacitors, as needed.
Reference Buffer 4 www.ti.com Reference Buffer The ADS1672 reference pins have switched capacitor inputs. At a clock rate of 20MHz (X1), a charge injection in and out of the ADS1672 reference input occurs. The external reference voltage that drives the ADS1672 reference pin must settle in less than 50ns. The REF5030 (U1) generates the 3.0V reference signal (Figure 3). The output of the REF5030 is heavily filtered to remove noise.
Digital Interface www.ti.com 6 Digital Interface It is easy to interface the ADS1672EVM board to multiple control platforms. The P2 connector (Figure 4, Samtec part number SSW-110-22-S-D-VS) provides a convenient digital access to the key ADS1672 I/O pins. Consult Samtec at http://www.samtec.com or call 1-800-SAMTEC-9 for a variety of mating connector options.
Digital Interface 6.1 www.ti.com Serial Data Interface, P2 The P2 connector (Table 3) is used for the digital interface to MMB0 and ADCPro. All logic levels on P2 are 3.3V CMOS. Table 3. P2: External Digital I/O Connector 8 Pin Number Signal P2.1 CS Description Chip select, active low P2.2 OTRD Digital filter out-of-range indicator. High on rising edge of DRDY. If conversion is in range, OTRD returns low on next rising edge of DRDY. P2.3 CLKX Serial transmit clock from processor.
Clock Source www.ti.com 6.2 Digital Control Signal PIN Configuration, SW1 When using the I2C function through U5 (with or without ADCPro connected), all SW1 switches should be in the OFF position (see Figure 4). The data clock and data out communications are directed through P2. All remaining ADS1672 digital control pins are configured with SW1. Table 4 describes the settings of the digital configuration switches.
Use as a Stand-Alone EVM www.ti.com W2 5VCC EN W3 Disconnect When Using External Clock INT MCLK EXT Internal or External Modular Clock Select Figure 6. W2 and W3 Jumpers for External Modulator Clock 8 Use as a Stand-Alone EVM The ADS1672EVM can be used as a stand-alone EVM, provided that the proper control signals are applied to serial input connector P2 (top or bottom side). The required power supplies (+5VA and +3.
EVM Operation www.ti.com 9.3 ADS1672EVM-PDK Power Supply The ADS1672EVM can be powered with the J4 connector or by attaching the MMB0 board. The MMB0 board provides the 5V and 3.3V power to the ADS1672EVM. Because the circuitry is provided on the ADS1672EVM, the complete system can be powered from the supplied +6V, 3A ac adapter. 9.4 Default Jumper Settings and Switch Positions Figure 8 shows the jumpers found on the EVM and the factory default conditions for each. Figure 8.
ADS1672EVM-PDK Kit Operation 10 www.ti.com ADS1672EVM-PDK Kit Operation This section provides information on using the ADS1672EVM-PDK, including setup, program installation, and program usage. CAUTION Do not connect the ADS1672EVM-PDK before installing the ADCPro software on a suitable PC. Failure to observe this caution may cause Windows to not recognize the ADS1672EVM-PDK as a connected device. To prepare Step 1. Step 2. Step 3. Step 4. Step 5. Step 6.
ADS1672EVM-PDK Kit Operation www.ti.com 10.2 Setting Up the ADS1672EVM-PDK The ADS1672EVM-PDK contains both the ADS1672EVM and the MMB0 motherboard; however, the devices are shipped unconnected. Follow these steps to set up the ADS1672EVM-PDK: Step 1. Unpack the ADS1672EVM-PDK kit. Step 2. Set the jumpers and switches on the MMB0 as shown in Figure 9. • Set the Boot Mode switch to USB. • Connect +5V and +5VA on jumper block J13 (if +5V is supplied from J14 +5VA).
ADS1672EVM-PDK Kit Operation www.ti.com 3. Plug the ADS1672EVM into the MMB0 as Figure 10 illustrates. Figure 10. Connecting ADS1672EVM to MMB0 CAUTION Do not misalign the pins when plugging the ADS1672EVM into the MMB0. Check the pin alignment carefully before applying power to the PDK. Step 3. 14 Set the jumpers and switches on the ADS1672EVM as shown in Figure 8 (note that these settings are the factory-configured settings for the EVM).
About the MMB0 www.ti.com 11 About the MMB0 The MMB0 is a Modular EVM System motherboard. It is designed around the TMS320VC5507, a DSP from Texas Instruments that has an onboard USB interface. The MMB0 also has 16MB of SDRAM installed. The MMB0 is not sold as a DSP development board, and it is not available separately. TI cannot offer support for the MMB0 except as part of an EVM kit. For schematics or other information about the MMB0, contact Texas Instruments. 11.
About the MMB0 11.1.2 www.ti.com Connecting a Laboratory Power Supply A laboratory power supply can be connected through terminal block J14 on the MMB0, as shown in Figure 12. To use a unipolar lab power supply configuration: • Disconnect J12 on the MMB0. • Connect a +5V dc supply to the +5VD terminal on J14. • Connect ground of the dc supply to the GND terminal on J14. It is not necessary to connect a +5V dc supply voltage to the +5VA terminal on J14 if the +5V/+5VA position on J13 is shorted.
About the MMB0 www.ti.com 11.2 Running the Software and Completing the Driver Installation Note: The software is continually under development. These instructions and screen images are current at the time of this writing, but may not exactly correspond to future releases. The program for evaluating the ADS1672EVM-PDK is called ADCPro. This program uses plug-ins to communicate with the EVM. The ADS1672EVM-PDK plug-in is included in the ADS1672EVM-PDK package.
About the MMB0 www.ti.com 2. Select ADS1672EVM from the EVM drop-down menu. The ADS1672EVM-PDK plug-in appears in the left pane, as shown in Figure 14. Figure 14. ADS1672EVM-PDK Plug-In Display Window Step 2. Step 3. Step 4. 18 The ADS1672EVM-PDK plug-in window has a status area at the top of the screen. When the plug-in is first loaded, the plug-in searches for the board. You will see a series of messages in the status area that indicate this action.
About the MMB0 www.ti.com Figure 15. Found New Driver Wizard, Screen 1 Figure 16.
About the MMB0 www.ti.com Figure 17. Found New Driver Wizard, Screen 3 Figure 18.
Evaluating with the ADCPro Software www.ti.com Figure 19. Found New Driver Wizard, Screen 5 Step 5. Step 6. Step 7. When Windows installs the software driver, the plug-in downloads the firmware to the MMB0. Windows will display the installation wizard a second time. Again, accept the default settings. The status area displays a connected message. The software is now ready to use. The Found New Driver wizard sequence should not appear again, unless you connect the board to a different USB port.
Evaluating with the ADCPro Software www.ti.com Settings on the ADS1672EVM correspond to settings described in the ADS1672 data sheet; see the ADS1672 data sheet (available for download at the www.ti.com) for details.
Evaluating with the ADCPro Software www.ti.com The Data Rate of a conversion is posted in the upper left corner of the ADC1672 plug-in screen. Under the Date Rate, a power-down switch can be implemented. This power-down affects the ADS1672 on the EVM board. Figure 24 shows the power-down option. Figure 24. Power-Down Option 12.1.
Schematics and Layout 13 www.ti.com Schematics and Layout Schematics for the ADS1672EVM are appended to this user's guide. The bill of materials is provided in Table 6. Note: Board layouts are not to scale. These figures are intended to show how the board is laid out; they are not intended to be used for manufacturing ADS1672EVM PCBs. 13.1 Bill of Materials Note: All components should be compliant with the European Union Restriction on Use of Hazardous Substances (RoHS) Directive.
Schematics and Layout www.ti.com Table 6. ADS1672EVM Bill of Materials (continued) Item No.
1 2 3 4 6 5 Revision History U8 +5VCC 1 DNC 2 C9 10uF VIN 3 4 GND U1 D 7 N/C TEMP 1 4 R33 6 OUT 3 C29 47uF C54 47uF +5VCC C62 4.7uF +5VCC R18 C26 R1 R48 383 C8 R47 NI RCM 16 15 E6 C57 7.5k AVDD AGND AGND AINN AINP AGND AVDD RBIAS AGND AGND AVDD AVDD VCM DGND DGND DGND R28 C39 4.7uF C20 0.1uF U6 ADS1672PAG 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 DVDD DGND DRDY DRDY DOUT *DOUT SCLK *SCLK RSV3 OTRD *CS START DRATE0 DRATE1 DVDD FPATH C44 4.
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