Octal configurable 1-A buck DC-DCs for multi-rail systems

Date
01/07/2013

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High-power octal 8 x 1-A buck DC-DC

Linear Technology's LTC3375 is a highly integrated general-purpose power management IC for systems requiring multiple low-voltage power supplies. The device features eight independent 1-A channels with I2C control, flexible sequencing, and fault monitoring in a compact QFN package. Each channel is a high efficiency synchronous step-down regulator with its own independent 2.25 to 5.5-V input supply and an output voltage range of 0.425 V to VIN. In addition, the LTC3375's buck DC-DCs may be connected in parallel to achieve higher output currents up to 4 A per output with a single shared inductor. Up to four adjacent regulators can combine, resulting in 15 different possible output configurations. All of the switching regulators are internally compensated and need only external feedback resistors to set the default output voltage. The LTC3375's pushbutton ON-OFF-RESET control, power-on reset, and watchdog timer provide flexible and reliable power-up sequencing and system monitoring. All buck output voltages are adjustable via I2C for margining or power optimization. The LTC3375 features a programmable and synchronizable 1- to 3-MHz oscillator with a 2-MHz default switching frequency. The device also contains a high-voltage input shunt-regulator controller, and quiescent current is only 11 μA with all DC-DCs off. It is well suited for a wide variety of multichannel applications including industrial, automotive, and communications systems. Adjacent buck regulators can combine in a master-slave configuration by connecting their VIN and SW pins together, and connecting the slave bucks' FB pin(s) to the input supply. The switching regulators offer two operating modes: Burst Mode operation (power-up default mode) for higher efficiency at light loads, and forced continuous PWM mode for lower noise at light loads. The I2C interface can select mode of operation, phasing, feedback regulation voltage, and switch slew rate. The bucks have forward and reverse current limiting, soft-start to limit inrush current during start-up, short-circuit protection, and slew rate control for lower radiated EMI. Other features include a die temperature monitor output (readable via I2C or the analog voltage on the TEMP pin), which indicates internal die temperature, and an OT (over-temperature) warning function, indicating high die temperature. The LTC3375 is available from stock in a thermally enhanced, low-profile (0.75-mm) 48-pin 7- x 7-mm exposed pad QFN package. E and I grades are specified over an operating junction temperature range of ?40 to +125 °C, and the H grade features operation from ?40 to +150 °C. 1000-piece pricing starts at $5.45 each for the E grade. Linear Technology

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