Buck-boost chipset for start-stop vehicle systems

October 25, 2018 //By Nick Flaherty
Buck-boost chipset for start-stop vehicle systems
ROHM has launched a buck-boost power supply chipset that provides the lowest current consumption in the industry along with stable performance (transient response characteristics) in automotive ECUs (Electronic Control Units) for cluster panels and gateways used in start-stop vehicle systems.

The chipset integrates a buck DC-DC converter with boost functionality (BD8P250MUF-C) and a dedicated boost chip (BD90302NUF-C). The primary BD8P250MUF-C uses ROHM’s novel buck-boost control technology, Quick Buck Booster, that enables configuration of a buck-boost power supply without degrading buck power supply characteristics by simply adding the dedicated BD90302NUF-C boost IC to the subsequent stage.

The result is a no-load current consumption of 8μA and ±100mV output voltage fluctuation utilizing an output capacitance 44μF,  which is 70% less current consumption and 50% less output capacitance than conventional products, contributing to improved stability and energy savings in applications where significant input voltage drops occur in a short period of time, such as start-stop vehicle systems. The Quick Buck Booster technology also allows a common board design that integrates both buck-boost and buck power supply topologies along with the requisite peripheral components and noise countermeasures, reducing development time and labor by 50% compared to conventional methods requiring separate buck-boost and buck power supply boards. 

In stop-start systems, a buck-boost power supply is required to prevent malfunctions due to low battery voltage during idling and battery fluctuations (cranking) immediately after start-stop operation, but conventional products are problematic from the standpoint of current consumption and responsiveness, increasing the demand for an improved solution as the number of stop-start vehicles continues to rise. 

To meet market demands, the BD8P250MUF-C integrates a spread spectrum function as a countermeasure against noise (EMI), allowing it to clear the international standard (CISPR 25) for noise in the automotive sector. At the same time, ROHM's original ultra-high-speed pulse control technology Nano Pulse Control is utilized to enable high speed operation at 2.2MHz that eliminates the effects on the AM radio band (1.84MHz max.), making it possible to achieve stable 5V output for ECU drive from high-voltage 36V input. This ensures low electromagnetic interference while enabling low voltage output from high voltage input without AM radio band interference, contributing to stable operation in automotive systems

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