DEMO MANUAL DC241C LTC1535 Full Duplex, Isolated RS485 Transceiver with Slew Limiting DESCRIPTION Demonstration circuit 241C showcases the LTC 1535 iso- RS485 Interface lated RS485 transceiver. The LTC1535 features 2,500V The right-hand side contains the isolated RS485 section. isolation the left-half of the chip contains familiar The chip is designed for full duplex operation. So the RS485 logic functions and an isolated switching converter, receiver input A-B and driver output Y-Z are brought out and the right-half contains the RS485 transceiver. Both to small terminals. The receiver also has a local output sides include a communications section to send data back RO2. Larger terminals V and GND2 are powered from CC2 and forth across the internal capacitive isolation barrier. the transformer, and require no external power. They are The LTC1535 allows the user to break ground loops that included for the purpose of monitoring the isolated con- cause problems in large systems, and it can also handle verter output. high common mode swings relative to ground without Other DC241C Features loss of data. Both sides have green LEDs (D1, D3) for monitoring Isolation Considerations the presence of power. A 3.3k series resistor makes for The board, as constructed, is designed for 500V isolation, dim viewing, but conserves current. For accurate power limited by the CTX02-14659 transformer. A full 3750V UL supply current measurement disable the LEDs with JP1 approvable transformer is also available from Coiltronics andJP3. as CTX02-14608. Note that the LTC1535 meets only a 120, 1/4W terminations are included. They are selected 2,500V test. See the LTC1535 data sheet for additional with jumpers JP4 (receiver) and JP5 (driver). information an other transformer options. Half-duplex operation is simplified by S1, which simply Logic Interface shorts A to Y and B to Z. Half to the left, full to the right. The left-half of DC241C contains the logic interface sec- The driver slew rate is controlled by JP2 slow left and tions. Large terminals are provided for +5V and logic fast right. ground (V and GND1). The input current is approxi- CC1 Terminal block J1 is the fastest way to graft DC241C into a mately 94mA. The smaller terminals connect to RO system. J1 requires a 2mm screw driver (Xcelite P3321 (receiver output), RE (receiver enable), DE (driver enable), recommended). Xcelite R181 wont fit no matter how hard and DI (driver input). The terminals are arranged to match you push. the LTC485 industry-standard pinout. Design files for this circuit board are available. All registered trademarks and trademarks are the property of their respective owners. UG-1405 Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications 1 subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.DEMO MANUAL DC241C ESD Caution ESD (electrostatic discharge) sensitive device. Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality. 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