Ultra-Compact High Efficiency Power Supplies for Automotive Applications

In recent years the increasing popularity of electric and hybrid vehicles has led to more sophisticated electronic systems and a greater demand for microcontrollers and memory. Conventional LDO regulators are commonly used, but they feature poor efficiency and cannot meet higher current demands. As a result, DC/DC converters, which provide greater efficiency and higher current-handling capability, are becoming the preferred solution. However, they are not without their drawbacks, which include more external parts and consequently a larger mounting area, increasing circuit design complexity significantly. With the trend towards improved performance and decreasing model cycles in the automotive industry comes a need for easier-to-use, high efficiency power supply ICs that lighten the design load and minimize mounting area.

A primary factor in the number of external components used with power supply ICs is the phase compensation circuit required to maintain a stable output voltage. Normally external capacitors and resistors are used to set the desired characteristics. However, ROHM was able to successfully optimize the phase compensation circuit internally, reducing parts count by 80% and contributing to more compact automotive systems. In addition, phase compensation adjustment, which is a common problem with power supply designs, is no longer required, shortening design time significantly.

ROHM power supplies utilize synchronous rectification for high efficiency operation, in combination with Light Load Mode, ensuring superior performance with low current consumption under all load conditions.

Availability: Now (Samples), July 2013 (OEM Quantities)

Key Features
1. Built-in phase compensation circuit and feedback resistors reduce the number of external parts and shorten the design cycle
Power supply ICs require a phase compensation circuit in order to ensure stable operation and prevent malfunctions. The BD905xx series integrates an optimized phase compensation circuit that reduces the number of external components considerably, simplifying set design while minimizing mounting area.

2. Compact package
The HTSOP-J8 package reduces volume by approx. 80% compared with conventional products. (6.0mmx4.9mm, t=1.0mm max.)








3. Low heat generation simplifies thermal design
Loss is a miniscule 1/10th the level of conventional LDO regulators (see figure at right), resulting in minimal heat generation. This simplifies thermal countermeasures, making it ideal for microcontrollers and DDR memory used in today’s vehicles that require greater current consumption.

4. Synchronous rectification and Light Load Mode ensure high efficiency operation
Synchronous rectification, coupled with Light Load Mode, results in over 90% efficiency (max.) under all load conditions for minimal current consumption.

5. Wide lineup
ROHM offers models in different output voltages and currents designed for various automotive systems (1.2V for microcontroller cores, 1.5V and 1.8V for DDR memory).




Terminology
• Feedback Resistor
A resistor that feeds back a portion of the output to the input for characteristics compensation in opamps and oscillation circuits.
• DDR (Double Data Rate) Memory
A type of memory that transfers data approximately twice as fast as conventional memory.
• PWM (Pulse Width Modulation)
A modulation method commonly used as a control signal in a variety of devices.