作者：Linear 文章来源：Linear
Linear公司的LTC2870/LTC2871是多模式RS232/RS485收发器,支持RS232,RS485和RS422协议,工作电压3V-5.5V. LTC2870可配置成两个单端RS232收发器重或一个差分RS485,而LTC2871提供两个RS232收发器和一个RS485收发器的独立控制.主要用在灵活的RS232/RS485/RS422接口,软件选择的多协议接口端,POS终端,电缆中继器和协议转换器.本文介绍了LTC2870/LTC2871主要特性,方框图以及各种通信配置框图.
LTC2870/71:RS232/RS485 Multiprotocol Transceivers with Integrated Termination
The LTC2870/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 fordiagnostic 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
LTC2870/LTC2871主要特性:
One RS485 and Two RS232 Transceivers
3V to 5.5V Supply Voltage
20Mbps RS485 and 500kbps RS232
Automatic Selection of Integrated RS485 (120Ω) and RS232 (5kΩ)Termination Resistors
Half-/Full-Duplex RS485 Switching
High ESD: ±26kV (LTC2870), ±16kV (LTC2871)
Logic Loopback Mode
1.7V to 5.5V Logic Interface
Supports Up to 256 RS485 Nodes
RS485 Receiver Failsafe Eliminates UART Lockup
Available in 28-Pin 4mm 5mm QFN and
TSSOP (LTC2870), and 38-Pin 5mmx7mm QFN and TSSOP (LTC2871)
LTC2870/LTC2871应用:
Flexible RS232/RS485/RS422 Interface
Software Selectable Multiprotocol Interface Ports
Point-of-Sale Terminals
Cable Repeaters
Protocol Translators
图1.LTC2870方框图
图2. LTC2871方框图
图3.LTC2870共享I/O的各种通信配置框图
图4.LTC2870用于半双工RS232或RS485的外接连接器配置框图
图5.LTC2871各种通信配置框图
图6.LTC2870采用外接连接器的更多通信配置框图
图7.LTC2871采用RS232到RS485转换的RS232扩展电缆连接框图
图8.LTC2870/71 RS485全双工网络框图
图9.LTC2870/71典型的电源连接框图