LTC2870/LTC2871 - RS232/RS485 Multiprotocol Transceivers with Integrated Termination - Linear Technology - #1

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LTC2870/LTC2871 1 28701f TYPICAL APPLICATIONS DESCRIPTION RS232/RS485 Multiprotocol Transceivers with Integrated Termination The LTC®2870/LTC2871 are robust pin-configurable multiprotocol transceivers, supporting RS232, RS485, and RS422 protocols, operating on a single 3V to 5.5V supply. The LTC2870 can be configured as two RS232 single-ended transceivers or one RS485 differential transceiver on shared I/O lines. The LTC2871 offers independent control of two RS232 transceivers and one RS485 transceiver, each on dedicated I/O lines. Pin-controlled integrated termination resistors allow for easy interface reconfiguration, eliminating external resistors and control relays. Half-duplex switches allow four-wire and two-wire RS485 configurations. Loopback mode steers the driver inputs to the receiver outputs for diagnostic self-test.The RS485 receivers support up to 256 nodes per bus, and feature full failsafe operation for floating, shorted or terminated inputs. An integrated DC/DC boost converter uses a small inductor and one capacitor, eliminating the need for multiple supplies for driving RS232 levels. 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. Protocol Switching with Automatic Termination Selection FEATURES APPLICATIONS n One RS485 and Two RS232 Transceivers n 3V to 5.5V Supply Voltage n 20Mbps RS485 and 500kbps RS232 n Automatic Selection of Integrated RS485 (120Ù) and RS232 (5kÙ)Termination Resistors n Half-/Full-Duplex RS485 Switching n High ESD: ±26kV (LTC2870), ±16kV (LTC2871) n Logic Loopback Mode n 1.7V to 5.5V Logic Interface n Supports Up to 256 RS485 Nodes n RS485 Receiver Failsafe Eliminates UART Lockup n Available in 28-Pin 4mm × 5mm QFN and TSSOP (LTC2870), and 38-Pin 5mm × 7mm QFN and TSSOP (LTC2871) n Flexible RS232/RS485/RS422 Interface n Software Selectable Multiprotocol Interface Ports n Point-of-Sale Terminals n Cable Repeaters n Protocol Translators Simultaneous Protocols and RS485 Termination Switching RS485 Duplex Switching 28701 TA01 LTC2870 1.7V TO VCC 3V TO 5.5V 1.7V TO VCC 3V TO 5.5V 1.7V TO VCC 3V TO 5.5V RS485 TERMINATION RS485 DUPLEX 485/232 DY Y Z A B DZ RA RB Y Z A B DI VL TE485 RO DIN1 ROUT2 DIN2 ROUT1 VL VCC VCC DOUT1 RIN2 DOUT2 RIN1 LTC2871 120Ù 120Ù Y VCC Z A B DI, DY RO, RB H/F LTC2870, LTC2871 FULL HALF RS232 RS485 OFF ON VL