New Step-Down Power Supply IC from ROHM Masters the Challenges of 48 V Automotive Systems

ROHM Semiconductor has recently announced the BD9V100MUF-C, a DC/DC converter with built-in MOSFET that can generate output voltages of just 3.3 V or 5 V (minimum 2.5 V) from input voltages up to 60 V at a switching frequency of 2 MHz. The IC therefore achieves the highest step-down ratio in the industry – 24:1 – between input and output voltages.

To obtain this voltage ratio, the chip uses ROHM’s proprietary Nano Pulse Control technology, which leverages high-voltage BiDCMOS processes and ultra-high-speed pulse control to realise an unprecedented ON time of just 9 ns. The new technology enables single-stage voltage conversion in 48 V systems such as those used in mild hybrid vehicles. At 2 MHz the number of parts required is halved, reducing application size and simplifying system design, while high-frequency operation also permits the use of smaller external components, e.g. coils and output capacitors.

Trend towards 48 V systems

Energy savings and environmental performance are the driving force behind constant innovation in the auto industry. Through optimised power distribution, mild hybrid vehicles with 48 V systems achieve significantly lower energy and fuel consumption, which in turn reduces CO2 emissions. Active systems for enhanced comfort in automobiles, such as brake-by-wire or electric power steering, increase the electrical power requirements. In traditional 12 V systems, electrical energy has to be transported to loads at a low voltage level, causing increased losses in the wiring harness. The need for thicker copper wires also adds weight, with a negative impact on fuel consumption. Using 48 V technology cuts the amount of electricity transferred by a quarter, so reducing losses in the wiring.

At system level, automobile electronics and sensors typically require a supply voltage of between 1 V and 5 V. This means that the 48 V bus voltage has to be stepped down to the lower voltages. At the same time, it makes sense to operate the DC/DC converter at 2 MHz, as this will not affect the AM radio band (1.84 MHz max.) and allows the most compact solution.

To date, no power supply IC has achieved both a high conversion ratio and a high switching frequency. A two-stage solution meets these requirements, but has various disadvantages: it takes up more space, uses more components, and is a more complex system. Now, with the BD9V100MUF-C, ROHM is offering a single-stage voltage conversion solution.

Nano Pulse Control

Nano Pulse Control refers to ultra-fast pulse control technology achieved by combining analogue circuit design, layout and processes utilising ROHM’s vertically integrated production system. This contributes to greater miniaturisation and system simplification in 48 V applications ranging from mild hybrid vehicles and industrial robots to base station sub power supplies.

Technical Data

Technical specifications for the BD9V100MUF-C DC/DC converter, sized at just 4.0 mm x 4.0 mm x 1.0 mm (W x D x H), include an input voltage range from 16 V to 60 V, output voltages from 0.8 V to 5.5 V with ±2 % accuracy, and a switching frequency of 1.9 to 2.3 MHz. The maximum output current is 1 A. The operating temperature range is between -40 °C and +125 °C.

Availability

Samples of the BD9V100MUF-C are available now, OEM quantities from December 2017.