DEMO MANUAL DC2542A LTC2358-18 Isolated Industrial Data Acquisition Board DESCRIPTION Demonstration circuit 2542A is a reference design for robust industrial data acquisition applications based on the LTC2358-18. The LTC2358-18 is capable of high voltage measurements with a large input common range; however, the DC2542A implements input protection that allows up to 400V of continuous input protection. Combined with gas discharge tubes, which provide protection from surges, the DC2542A is capable of surviving extreme abuse. The digital interface is an HSMC (high-speed mezzanine connector), which is compatible with Altera Cyclone V SoCkit and other Altera FPGA evaluation boards that support 3.3V CMOS I/O. This reference design includes the LTC2358-18 SAR ADC, LTM2893-1 digital isolator, ADA4522-2 dual zero-drift operational amplifier, and an LT6658 dual-output, high current reference for sensor excitation. Design files for this circuit board are available at http://www.linear.com/demo/DC2542A This demo manual covers the basic functionality of the DC2542A. Refer to the design files for schematic and parts list/bill of materials. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Analog Devices, Inc. All other trademarks are the property of their respective owners. –16V*GND 16V ±10.24 INPUT –16V *GND 16V HSMC INTERFACE TO SoCKit BOARD (3.3V I/O) ±10.24 INPUT *THE SPLIT SUPPLY CAN BE CONNECTED FROM THE TURRETS OR FROM THE TERMINALS Figure 1. Connection Diagram dc2542af 1 DEMO MANUAL DC2542A QUICK START PROCEDURE 1) Prepare the SoCkit board and SD card image as described here: http://www.linear.com/solutions/7704 11) Enter the IP address from the SoCkit LCD screen in the SOCKIT_IP argument. Click Run. 2) Install the LinearLabTools software package from: http://www.linear.com/linearlabtools 12) If the script reports an incorrect FPGA bitstream file, log into the SoCkit board using an SSH client such as Putty on Windows, or directly from a terminal in Mac or Linux. The user name is “sockit”, and the password is “sockit”. 3) Follow the procedure for Installing Python: http://www.linear.com/docs/52543 4) Carefully mount the DC2542A to the SoCkit board via the HSMC connector, using 5 mm standoffs between the boards and tighten the mounting screws. 5) Connect the SoCkit board to a network with a DHCP server, or connect directly to host computer’s Ethernet jack or USB-Ethernet adapter. 6) Apply ±16V to the indicated terminals. Refer to Figure 1 for locations. 7) Apply a low noise, low distortion signal source to J1 and J2. 8) Power up the SoCkit board using the 12V adapter. 9) After approximately 30 seconds, the FPGA_CONF_D LED will illuminate, the board’s IP address will show in the LCD display, and LED1 and LED2 will blink at different rates. Run these commands: cd fpga_bitfiles rm default.rbf ln --symbolic DC2542A.rbf default.rbf sudo program_fpga.sh default.rbf (enter “sockit” for the password) This only needs to be done once, the correct FPGA bitstream file will be loaded automatically the next time the board boots. The script will capture data and display each channel in its own window. Figure 2 shows the captured data. 10) Open Spyder (the Anaconda Python Debugger) Click file -> open Navigate to the location where LinearLabTools is installed. Open this script: \python\llt\demo_board_examples\ ltc23xx\ltc2358\ Open ltc2358_dc2542a_a.py 2 dc2542af DEMO MANUAL DC2542A QUICK START PROCEDURE Figure 2. Screen Capture for Channel 0 CIRCUIT DESCRIPTION Input Protection The DC2542A features input protection circuits. The first line of defense is the use of a back to back depletion mode NMOS circuit. This circuit limits the input current to ±3mA up to a maximum of 400V. The second line of defense is the use of low voltage gas discharge tubes (GDT). This will protect downstream components from fast transients such as high voltage surges. Figure 3 shows the input protection circuit. IN+ LND150 ADA4522-2 LND150 + – R1 GDT DEPLETION MODE NMOS LIMIT TRANSIENT CURRENT TO ±3mA MAX UP TO 400V IN– LND150 ADC IN+ FAST TRANSIENT AND >400V PROTECTION LND150 R2 R3 + – ADC IN– ADA4522-2 GDT DC2542A F03 Figure 3. DC2542A Input Protection dc2542af 3 DEMO MANUAL DC2542A CIRCUIT DESCRIPTION Driving Sensors with LT6658 Using External References for the LTC2358 The DC2542A is fitted with an LT6658-5. The high output drive is exposed on J3 labeled VSENSOR. The LT6658 can drive up to 150mA and can be used to drive low impedance sensors such as Wheatstone bridges. Figure 4 shows how to connect the LT6658 to a number of Wheatstone bridge type sensors, but it can be used to drive other type of sensors. The DC2542 can be configured to accept external references for the LTC2358. Move JP1 from internal (INT) to external (EXT) position and connect the external reference to the turret labeled REFBUF. To use the LT6658 as the reference, stuff R14 with a 0Ω 0402 resistor. 350 V+ IN OUT2 J3 (VSENSOR) LT6658-5 SHDN BYPASS GND 120 TO ADC 1k DC2542A F04 Figure 4. Driving Low Impedance Sensors with the LT6658 4 dc2542af DEMO MANUAL DC2542A EXTERNAL CONNECTIONS Connections: Turrets: P1: (Reverse side of the board) - HSMC digital interface. 3.3V CMOS digital signals to and from the ADC, as well as auxiliary signals. It provides 3.3V power from the FPGA board to the non-isolated side of the DC2542A. E1: REFBUF - LTC2358 reference pin. J1, J2: 12-pin terminal block. IN0+/IN0– through IN3+/ IN3– on J1, IN4+/IN4– through IN7+/IN7– on J2 - provide analog input voltages to AIN0-AIN7 via the ADA4522-2. E2: +16V/+18V - Positive input for isolated analog supply. A maximum of 20V can be applied. E3: GND - Grounded input for isolated analog supply. E4: VCC - LTC2358-18 positive high voltage power supply, nominally 15.25V set by U3. J3: 12-pin terminal block. LT6658 OUT2 is connected in common to four VSENSOR terminals for sensor excitation. +16V, GND, –16V terminals for analog isolated supply. E5: VCCIO - LTC2358-18 digital supply, nominally 3.28V set by U4. J4: 14-pin connector with 3.3V logic levels. This connector is intended for advanced features which allows the FPGA to connect to demo boards with a SPI interface. Contact the factory for support. E7: -16V/-18V: Negative input for isolated analog supply. A maximum of –20V can be applied. JP1: REF - selects internal (INT) or external (EXT) reference for the ADC. The default setting is INT. JP2-JP17: GAIN - set the gain of the ADA4522-2 to either unity gain (G1) or a gain of 37 (G37). The default position is G1. Both jumpers for a given ADA4522-2 must be set to the same gain position. E6: VDD - LTC2358-18 VDD power supply, nominally 5V. E8: VEE - LTC2358-18 negative high voltage power supply, nominally –15.25V set by U6. E9: 3.3V - Supply for onboard clock and LTM2893-1 logic side. Normally supplied from the FPGA board via P1. May be powered externally by removing F1. E10: FPGA_GND - FPGA ground. JP18: EEPROM is for factory use only. The default position is WP. dc2542af Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 5 DEMO MANUAL DC2542A DEMONSTRATION BOARD IMPORTANT NOTICE Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES. The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.). No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged. This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer. Mailing Address: Linear Technology 1630 McCarthy Blvd. Milpitas, CA 95035 Copyright © 2004, Linear Technology Corporation 6 dc2542af LT 0917 • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2017