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Isolated_RS_485_RS_422_data_interface

2016-10-12 15:32  
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Isolated_RS_485_RS_422_data_interface
Isolated_RS_485_RS_422_data_interface
Isolated_RS_485_RS_422_data_interface
Figure 3-1 shows the typical application circuit for the MAX1480A/B. These ICs are complete, electrically isolated RS-485/RS-422 data-communications interfaces. Transceivers, opto-couplers, and a transformer provide a complete interface in one 28-pin package. Figure 3-2 shows the pin descriptions. Figures 3-3 and 3-4 show the function tables. The MAX1408B has reduced-slew-rate drivers that minimize EMI (electromagnetic interference) and reduce reflections caused by improperly terminated cables, allowing error-free data transitions at data rates up to 250 kbps. The MAX1480 driver slew rate is not limited, allowing transmission rates up to 2.5 Mbps. The ICs draw 28 mA of quiescent current. The MAX1408B provides a low-power shutdown mode that consumes only 0.2μA. The drivers are short-circuit current-limited and are protected against excessive power dissipation by thermal shutdown circuits that place the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high output if the input is open circuit. The ICs typically can withstand 1600 Vrms for one minute or 2000 Vrms for one second. MAXIM NEW RELEASES DATA BOOK, 1995, P. 2-13, 2-15, 2-17