Linear Reduces Component Count and Boosts Efficiency

Linear Technology Corporation introduces the LTC2870 and LTC2871 multiprotocol transceivers with switchable integrated termination for 3.3V and 5V systems. RS485 systems require a termination resistor on the ends of the communication bus to minimize signal reflections. Both the LTC2870 and LTC2871 integrate pin-controlled termination resistors that allow for easy interface reconfiguration, eliminating external resistors and control relays. The termination resistors, when enabled, are automatically switched on or out to match the transceiver's protocol selection of RS232 or RS485. Both devices also feature high ESD protection: ±26kV HBM (LTC2870) or ±16kV HBM (LTC2871) on the transceiver bus pins, when powered off or operating. The LTC2870 can be configured as two RS232 single-ended transceivers or one RS485 differential transceiver on shared I/O lines, whereas the LTC2871 offers independent control of two RS232 transceivers and one RS485 transceiver, each on dedicated I/O lines. Both devices reduce component count for multiprotocol networks and offer on-the-fly configurability. The LTC2870 and LTC2871 are suitable for a wide variety of applications, including software-selectable multiprotocol interface ports, point-of-sale terminals, security cameras, cable repeaters and protocol translators. An optional 1.7V to 5.5V logic supply enables convenient digital interfacing, and an integrated DC/DC boost converter eliminates the need for multiple supplies to drive RS232 levels. Drivers and receivers can be independently disabled, leaving them in a high impedance state, consuming only 9uA in a low power shutdown mode. Aside from automatic termination selection, both devices provide half- and full-duplex RS485 switching and a logic loopback mode that steers the driver inputs to the receiver outputs for diagnostic self-test and debug. Other protective measures include high ESD of ±4kV or better on all pins, thermal shutdown protection and a full failsafe RS485 receiver for floating, shorted or terminated inputs that eliminates the need for external network biasing resistors and UART lockup. Summary of Features: LTC2870/71 • 3V to 5.5V Supply Voltage Range • One RS485 & Two RS232 Transceivers • 20Mbps RS485 & 500kbps RS232 • Automatic Selection of Integrated RS485 (120Ohm) & RS232 (5kOhm) Termination Resistors • Logic Loopback Mode • High ESD: ±26kV (LTC2870) or ±16kV (LTC2871) on Line I/O; ±4kV on All Other Pins • 1.7V to 5.5V Logic Interface • Supports up to 256 RS485 Nodes • Full Failsafe RS485 Receiver Eliminates UART Lockup • Available in 28-Pin 4mm x 5mm QFN & TSSOP (LTC2870), & 38-Pin 5mm x 7mm QFN & TSSOP (LTC2871) The LTC2870 is available in 28-pin 4mm x 5mm QFN and TSSOP packages, and the LTC2871 is available in 38-pin 5mm x 7mm QFN and TSSOP packages. Both devices are available today in production quantities. Please visit www.linear.com/2870 for more product selection and information.

Linear Technology Corporation announces the LTC3789, a very high efficiency (up to 98%) synchronous buck-boost DC/DC controller that operates from input voltages above, below or equal to the regulated output voltage. High power circuits that step-up and-down typically rely on transformers or two DC/DC converters, one for step-up (boost) and the other for step-down (buck) conversion. The LTC3789 operates using a single inductor with 4-switch synchronous rectification and can deliver output power up to 150W with a single device. Even higher output power can be achieved when multiple circuits are paralleled. The LTC3789 operates with a selectable fixed frequency between 200kHz and 600kHz, and can be synchronized to an external clock over the same range with its integrated phase-locked loop (PLL). Its wide 4V to 38V input range, 0.8V to 38V output range and seamless transitions between operating modes make it ideal for a wide range of industrial controls, automotive, solar and high power battery-supplied systems. The LTC3789 employs a proprietary current-mode control architecture for constant frequency operation in buck or boost mode and has powerful onboard quad N-channel MOSFET gate drivers. The LTC3789 also provides an accurate, constant-current regulation loop for either input or output current, over a wide input voltage range. The input current limit function prevents overloading of the input source, and the output current limit provides an easy solution for regulated output current applications such as battery charger or LED drivers. Fault protection is provided for overvoltage, overcurrent and short circuit conditions in all operating modes. In addition, the LTC3789 disconnects the input voltage from the output when in shutdown. The user can select continuous or pulse skip mode to maximize light load efficiency. Furthermore, the LTC3789 has adjustable soft-start, a power good output and maintains ±1.5% reference voltage accuracy over an operating junction temperature range of -40°C to 125°C. Summary of Features: LTC3789 • Single Inductor Architecture • Operation with Input Voltages Above, Below or Equal to the Output Voltage • 4V to 38V Input Voltage Range • 0.8V to 38V Output Voltage Range • Programmable Input or Output Current Limit • Synchronous Rectification • Up to 98% Efficiency • On Chip MOSFET Gate Drivers • 150 Watts Output Power Capable • Output Disconnect During Shutdown • PLL Fixed Operating Frequency from 200kHz to 600kHz • Power Good Output Signal • ±1.5% Reference Voltage Accuracy over -40oC to +125oC • Current-Mode Control for Fast Transient Response & Easy Loop Compensation • Overvoltage and Overcurrent Protection • 5.5V Internal & External VCC LDOs The LTC3789 is available in 28-pin 4mm x 5mm QFN and 28-lead SSOP packages. For more information, visit www.linear.com/3789. www.linear.com