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1 Aug 2019, 10:27

Ultra-Compact Automotive Grade Buck DC/DC Converters

Offer high efficiency and reliable supplies for sensors and cameras to contribute to the evolution of safe assisted driving

The automotive-qualified BD9S series (BD9S400MUF-C, BD9S300MUF-C, BD9S200MUF-C, BD9S100NUX-C, BD9S000NUX-C) of automotive synchronous secondary buck DC/DC converters have high reliability with reduced power usage in a condensed package with an operating temperature range of -40 to +125 degrees. The components are offered with wettable flanks in a leadless package. The BD9S series is therefore ideally suited for use within radars, cameras and sensor applications for use with autonomous driving.

The increasing requests for safety systems require the implementation of collision avoidance systems in the evolution of self-driving cars. Therefore the increased use of onboard safety systems requires a significant number of subsystems consequently demanding higher power consumption. At the same time, consideration is required to reduce component count and PCB area in order to minimise vehicle weight.

With these challenges in power supply design, ROHM delivers class-leading* performance incorporating its design and manufacturing technologies with a fully integrated production system.

The BD9S series comprises of a very compact, automotive-grade power supply ICs that includes an enable function in order to adjust the startup time and a PGOOD output indication to improve system functional safety.

This broad lineup of Buck DC/DC converters supports output currents from as little as 0.6 up to 4.0A. It is available in industry-leading* 2 and 3mm2 packages which can provide high efficient operation, resulting in a best-in-class power conversion efficiency of 90% (at 3.6V input/1.8V output). Furthermore, the current mode control ensures fast response to load transients and combined with a fixed 2.2MHz switching frequency, it avoids interference within the AM Band. This higher frequency ensures that the application can take advantage of using smaller external components, which ultimately supports a higher degree of miniaturization and power savings.

 Main Features

  1. Enable control and Output voltage indicator to improve system reliability

This series of DC/DC contains an enable function to adjust the startup time and a built-in output (Power Good function) indicating the correct output voltage has been attained.  

      2. Class-leading miniaturization and efficiency

Within the automotive arena, designers are tasked with reducing footprints for the ever-challenging task of saving PCB board space and cost. The BD9S series of buck DC/DCs has a class-leading 2mm2 size which is fully synchronous while the optimized design ensures the best-in-class* power conversion efficiency among functionally equivalent products (90% at 3.6V input/1.8V output).

The current mode control loop with fixed 2.2MHz frequency makes it possible to reduce the size of peripheral components and eliminate interference from the AM radio band. A dedicated light load mode (SLLM™) provides excellent efficiency during light-load conditions, making the BD9S series suitable for reducing standby power consumption. 

     3 Broad lineup includes output currents up to 4.0A

ROHM offers ultra-compact models in output currents ranging from 0.6A to 4.0A. This contributes to model optimization and provides system flexibility and choice.

Application Examples

  • ADAS sensors, cameras, and radars
  • Drive recorders
  • Other automotive applications requiring high efficiency, superior reliability, and greater compactness


*ROHM September 2018 study

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1 Aug 2019, 10:27