April 3, 2012 – Linear Technology Korea (CEO Hong Sa-kwak) announced the release of the LTC2872, a multiprotocol transceiver with integrated switchable termination for 3.3V and 5V systems. RS485 systems require termination resistors at the ends of the communication bus to minimize signal reflection. The LTC2872 features an integrated pin-controlled termination resistor, allowing for easy interface reconfiguration and eliminating the need for external resistors or control relays. When enabled, the termination resistor automatically switches in or out, matching the transceiver's RS232 or RS485 protocol selection. This device features high ESD protection, providing ±16kV HBM on the transceiver bus pins during power-off or operation. The LTC2872 can be configured with four RS232 single-ended transceivers, two RS485 differential transceivers, or a combination of both on a shared I/O line. This reduces the number of components for multiprotocol networks and provides on-the-fly configurability.
The LTC2872 is suitable for a wide range of applications, including software-selectable multiprotocol interface ports, PoS terminals, security cameras, cable repeaters, and protocol translators. Digital interfacing is made more convenient with logic supply selection options ranging from 1.7V to 5.5V, and it features an integrated DC/DC boost converter that eliminates the need for multiple supplies required to drive RS232 levels. The driver and receiver are individually disabled and kept in a high-impedance state, consuming only 9µA even in low-power shutdown mode. In addition to the automatic termination selection feature, the LTC2872 provides half/full duplex RS485 switching and logic loopback modes that send driver inputs to receiver outputs for self-testing and debug diagnostics. Furthermore, it offers various protection features, such as ESD of ±4kV or higher on all pins, thermal shutdown operation, and a safe full failsafe RS485 receiver for floating, short, or terminated inputs, thereby eliminating the need for external network biasing resistors and UART lockups.
The LTC2872 is available in a 38-pin 5mm x 7mm QFN package and is currently available for mass production. Pricing starts at $6.45 per unit for 1,000 units. For product selection and details, please refer to www.linear.com/product/LTC2872 .

Photo Caption: Simultaneous Protocol and RS485 Termination Switching

Product Features: LTC2872

• 4 RS232 and 2 RS485 transceivers
• Supply voltage range: 3V ~ 5.5V
• 20Mbps RS485 and 500kbps RS232
• Integrated RS485 (120Ω) and RS232 (5kΩ) termination resistor automatic selection function
• Half/Full Duplex RS485 Switching
• Logic Loopback Mode
• High ESD: ±16kV at I/O lines
• 1.7V ~ 5.5V logic interface
• Supports up to 256 RS485 nodes
• Remove UART lockup pin for RS485 receiver full fail-safe
• 38-pin 5mm x 7mm QFN package