MILPITAS, CA – November 10, 2009 – Linear Technology Corporation introduces the LTC3855, a dual output high efficiency (up to 95%) synchronous step-down DC/DC controller with multiphase operation, differential output voltage sensing and integrated phase-lock loop (PLL) synchronization. Up to 12 phases can be paralleled and clocked out of phase to minimize input and output filtering requirements for high current applications (up to 200A). The differential amplifier provides true remote output voltage sensing of both the positive and negative terminals, enabling high accuracy regulation where IR losses occur through vias, trace runs and interconnects. Applications include high current ASIC and FPGA supplies, power distribution buses, high power audio amplifiers and network servers.
The LTC3855 operates with all N-channel MOSFETs from input voltages ranging from 4.5V to 38V, and it can produce ±0.75% accurate output voltages from 0.6V to 12.5V. The output current is sensed by monitoring the voltage drop across the output inductor (DCR) or by using a sense resistor. Programmable DCR temperature compensation maintains an accurate and constant over current limit over a broad temperature range. The onboard 1.1Ohm gate driver minimizes MOSFET switching losses and allows the use of multiple MOSFETs connected in parallel. A fixed operating frequency can be programmed from 250kHz to 770kHz or can be synchronized to an external clock with its internal PLL. The device’s minimum on-time of just 90ns makes the LTC3855 ideal for high step-down ratio applications.
Tracking and sequencing functions allow the optimization of power-up and power-down of multiple power supplies. Additional features include current mode control, an onboard LDO for IC power, programmable soft start, two power good signals and external VCC control.
The LTC3855 is available in 38-lead SSOP or 40-lead 6mm x 6mm QFN packages. The LTC3855E operates from -40ºC to 85ºC, with the 1000-piece price starting at $3.18. The LTC3855I Industrial grade version operates from -40ºC to 125ºC, with a 1,000-piece price starting at $3.59 each. Both versions are available from stock. For more information, visit www.linear.com.
Summary of Features: LTC3855
Multiphase Operation – Up to 12 Phases
High Efficiency – Up to 95%
High Power – Up to 200A
Wide Input Voltage Range from 4.5V to 38V
Output Voltages Ranging from 0.6V to 12.5V
±0.75% Accuracy
RSENSE or DCR Current Sensing
Programmable DCR Temperature Compensation
Powerful 1.1Ohm Dual N-Channel MOSFET Gate Driver
True Differential Amplifiers for Remote Output Voltage Sensing
Output Voltage Tracking or Programmable Soft Start
Phase-Lockable Fixed Frequency from 250kHz to 770kHz
Current Mode Control for Accurate & Easy Current Sharing
High Power Dual Output Multiphase
DC/DC Controller
About Linear Technology
Linear Technology Corporation, a manufacturer of high performance linear integrated circuits, was founded in 1981, became a public company in 1986 and joined the S&P 500 index of major public companies in 2000. Linear Technology products include high performance amplifiers, comparators, voltage references, monolithic filters, linear regulators, DC-DC converters, battery chargers, data converters, communications interface circuits, RF signal conditioning circuits, µModule® products, and many other analog functions. Applications for Linear Technology’s high performance circuits include telecommunications, cellular telephones, networking products such as optical switches, notebook and desktop computers, computer peripherals, video/multimedia, industrial instrumentation, security monitoring devices, high-end consumer products such as digital cameras and MP3 players, complex medical devices, automotive electronics, factory automation, process control, and military and space systems.
