DEMO MANUAL DC2063A LTC2875 60V Fault Protected 3.3V or 5V High Speed CAN Transceiver Description Demonstration circuit 2063A is a robust high speed, low power, ISO 11898-2 compliant CAN transceiver featuring the LTC(R)2875. The demo circuit operates on 3.3V or 5V supplies and features 60V overvoltage fault protection on the data transmission lines during all modes of operation. The demo circuit contains all the components necessary to demonstrate the features of the LTC2875 in a CAN network, including a terminated SMB jack for TXD data input, jumper selectable CAN bus termination (supporting either single or split termination configurations), and a jumper selectable variable slew rate control. Design files for this circuit board are available at http://www.linear.com/demo/DC2063A L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Performance Summary Specifications are at TA = 25C SYMBOL PARAMETER CONDITIONS MIN TYP MAX VCC Input Supply Range 3.3V VCC Range 3.0 3.3 3.6 5V VCC Range 4.5 5.0 5.5 fMAX Maximum Data Rate JP3 in `MAX' position Interface I/O: CANH, CANL Bus Differential Voltage (CANH-CANL) 4 -60 JP2 in `SINGLE' or `SPLIT' position UNITS V V Mbps 60 V 10 V operating principles The LTC2875 is enabled by pulling the RS pin low. The slew rate of the transmitter can be controlled by pulling RS low with a resistor 200k, with the slew rate decreasing with increasing resistor value. The DC2063A provides two jumper positions to enable the LTC2875. With a jumper in the JP3:MAX position, the RS pin is grounded and the LTC2875 operates at its maximum slew rate. With a jumper in the JP3:ADJ position, the transmitter slew rate can be varied from its minimum to maximum using 200k variable resistor RV1. When no jumper is placed on JP3, the RS pin in the LTC2875 is pulled up by an internal 250k resistor, putting the chip in the shut-down state. The data input signal can be applied to the LTC2875 TXD pin through either the TXD turret or the SMB jack J1. To apply the TXD signal through the SMB jack J1, place a jumper on the JP1:SMB position. The SMB input is terminated to GND by a 50 resistor. To apply the TXD signal through the TXD turret, place a jumper on the JP1:TURRET position. The TXD turret input contains a 100 series resistor but is not terminated. Jumpers may be applied to both JP1:SMB and JP1:TURRET to enable applying a signal from a pulse generator through the SMB jack J1 and monitoring the signal with a scope probe on the TXD turret. dc2063af 1 DEMO MANUAL DC2063A operating principles When TXD is low, the LTC2875 drives the dominant state onto the CANH and CANL bus lines, with CANH pulled high and CANL pulled low. When TXD is high, the LTC2875 is in the recessive state, with both CANH and CANL drivers in the high impedance state, and the differential voltage on the CAN bus lines is returned to near zero by the termination resistors. The TXD pin is pulled high by an internal 500k resistor when it is left floating. The CAN bus must be terminated at both ends by resistors matched to the impedance of the bus cable, typically 120, while all other nodes on the CAN bus must be unterminated. The DC2063A provides three jumper selectable termination configurations: split termination, single termination, and no termination. The split termination is selected by placing two jumpers on JP2 in the SPLIT (vertical) configuration. This provides 120 termination consisting of two series 60 resistors with the LTC2875 SPLIT pin and a 4.7nF decoupling capacitor biasing the termination center point. This configuration lowers the EME of the transmitted signal by reducing common mode voltage fluctuations. The single termination is selected by placing two jumpers on JP2 in the SINGLE (horizontal) configuration. This provides 120 termination consisting of two series 60 resistors with no biasing of the center point. No termination may be selected by removing both jumpers from JP2. The LTC2875 receiver senses the differential voltage on the CAN bus lines and produces a digital output on the RXD pin. When a dominant state is sensed on the bus lines, the RXD output will pull low. When a recessive state is sensed on the bus lines, the RXD output will pull high. When the LTC2875 is in the shutdown state, the RXD pin is pulled high by an internal 500k resistor. The LTC2875 RXD pin is connected directly to the DC2063A RXD turret. Quick Start Procedure Demonstration circuit 2063A is easy to set up and evaluate the performance of the LTC2875. 1. Verify the jumpers are in the following default positions: JP1:SMB ON; JP1:TURRET OFF JP2: SPLIT JP3:MAX ON; JP3:ADJ OFF 2. With power off, connect the input power supply to VCC and GND turrets. NOTE: Make sure the input voltage does not exceed 6V. 4. Connect a function generator to SMB jack J1 and set to square wave with a low of 0V, high = VCC. Set frequency to 100kHz (200kbps). Enable output of function generator. 5. Connect oscilloscope to pin RXD and observe 100kHz waveform. This demonstration shows that data applied to TXD is transmitted to the CAN bus, looped back through the receiver, and outputted on RXD. 3. Turn on the power at the input. 2 dc2063af DEMO MANUAL DC2063A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER IC, CAN Transceiver LINEAR LTC2875IDD Required Circuit Components 1 1 U1 Hardware/Components (For Demo Board Only) 2 1 C1 Capacitor, 2.2F, 10%, 0603, 10V, X7R Murata/GRM188R71A225KE15D 3 1 C2 Capacitor, 4700pF 20% 0603, 100V, X7R AVX/06031C472MAT2A 4 1 C3 Capacitor, Tantalum, 6.8F, 10%, 3216, 16V AVX/TAJA685K016RNJ 5 2 E1, E2 Turret Mill Max/2308-2-00-80-00-00-07-0 6 2 E3, E4 Turret Mill Max/2501-2-00-80-00-00-07-0 7 1 J1 Connector, SMB Male Jack, Straight, 50 Amphenol/142138 8 1 J2 Terminal Block, 3 Position, Side Entry 3.5mm TE Connectivity/284391-3 9 3 JP1-3 Header, 2 x 2 0.1" Samtec/TSW-102-07-G-D 10 1 R1 Resistor, 49.9, 1%, 1210 Panasonic/ERJ-14NF49R9U 11 1 R2 Resistor, 100, 5%, 1206 AAC/CR10-101JM 12 2 R3, R4 Resistor 60.4, 1%, 1210 Vishay/CRCW121060R4FKEA 13 1 RV1 Trimmer, 200k, 1-Turn Panasonic/EVM-3VSX50B25 14 4 Standoff, Snap-on Keystone/8833 Schematic Diagram dc2063af 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. 3 DEMO MANUAL DC2063A 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 (c) 2004, Linear Technology Corporation 4 dc2063af Linear Technology Corporation LT 1014 * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com LINEAR TECHNOLOGY CORPORATION 2014