34V Input Synchronous Step-down DC/DC Controller for Automotive Applications

The R1272S is a step-down DC/DC controller which can generate an output voltage of 0.7V to 5.3V by driving external high- / low-side NMOSs. By the adoption of a unique current mode PWM architecture without an external current sense resistor, the R1272S can make up a stable DC/DC converter with high-efficiency even if adding low Ron MOSFETs and a low DCR inductor externally. And, by the frequency characteristics optimization with using external phase compensation capacitor, the R1272S can achieve a high-speed response to variations of input voltage and load current. The user-settable oscillation frequency is adjustable over a range of 250kHz to 1MHz by external resistors, and also can be synchronized to an external clock.
Output Voltage Control Methods have three operating modes: Forced PWM mode, PLL_PWM mode, and PWM/VFM Auto-switching mode. These modes are selectable according to conditions of the MODE pin.
Especially, the PWM/VFM Auto-switching mode can improve efficiency under light load conditions.
When the input voltage drops down at cranking, to hold the output voltage level, the R1272S reduces the offduty by decrease the operation frequency below one-quarter so that the input-output difference voltage becomes small.
Protection functions include a current limit function, an UVLO (Under Voltage Lock Out) function, an OVP (Over Voltage Protection) function, a soft-start function, a low-inductor current shutdown function, and so on. Also, a power good function provide the status of output with using a power good (PGOOD) pin.

For EMI reduction, SSCG (Spread-Spectrum Clock Generation) for diffused oscillation frequency at the PWM operation is optionally available.

• Power source for car accessories including car audio equipment, car navigation system, and ETC system.
• ・Power source for control units including EV inverter and charge control.

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