Historically, many of the existing multi-output PMICs have not possessed the necessary flexibility to handle these modern systems. Any solution to satisfy the automotive power management IC design constraints outlined above must combine a high level of integration, including moderate-current buck switching regulators with low voltage capability, wide temperature range of operation, and a high degree of flexibility. What’s needed is a multi-channel, configurable DC/DC converter to address all of these issues - one device - which can provide high levels of integration and configurability, while simultaneously satisfying the needs of numerous applications.
Flexible octal buck regulator
The LTC3375 is an integrated general-purpose power management solution for systems requiring multiple low voltage power supplies. The device features eight independent 1A channels with I2C 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 VIN. 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 VIN 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 I2C. 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 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 I2C) that indicates internal die temperature, and a die temperature (DT) warning function, which warns the user when the die temperature has reached its programmed alarm threshold, thereby allowing the system to take corrective action. The LTC3375 is available in a thermally enhanced, low profile (0.75mm) 48-pin 7mm x 7mm exposed pad QFN package. The LTC3375 is also available in a high temperature (H-Grade) option with a junction temperature rating from -40°C to +150°C, satisfying the high temperature automotive operating requirement.
Figure 1: LTC3375 simplified 3-output 4A / 3A / 1A block diagram Click on image to enlarge
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