Car infotainment systems need multi-output power ICs: Page 4 of 9

March 11, 2013 //By Nathan Hanagami, Steve Knoth and Marty Merchant
Car infotainment systems need multi-output power ICs
Nathan Hanagami, Steve Knoth and Marty Merchant of Linear Technology examine why car infotainment systems need multi-output power ICs.
low voltage power supplies. The device features eight independent 1A channels with I 2C control, flexible sequencing and fault monitoring in a compact QFN package. The LTC3375 contains eight internally compensated, high efficiency synchronous step-down regulators plus a high voltage always-ON linear controller. Each buck regulator has its own independent 2.25V to 5.5V input supply and an output voltage range of 0.425V to V IN. The device’s pushbutton ON/OFF/RESET control, power-on reset and watchdog timer provide flexible power-up sequencing and system monitoring. The LTC3375 features a programmable and synchronizable 1MHz to 3MHz oscillator with a 2MHz default switching frequency. Quiescent current is 11µA with all DC/DCs off, saving power in always-on systems. It is suitable for various multichannel applications including industrial, automotive and communications systems.

The LTC3375’s eight buck converters can be used independently or connected in parallel to achieve higher output currents up to 4A per output with a single shared inductor. Since up to four adjacent regulators can be combined, there can be 15 different possible output configurations. Adjacent buck regulators can be combined in a master-slave configuration by connecting their V IN and SW pins together, and connecting the slave bucks’ FB pin(s) to the input supply. All of the switching regulators are internally compensated and need only external feedback resistors to set the output voltage. Additionally, the output voltages can be adjusted via I 2C. 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 I 2C interface can be used to 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 I 2

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