ROHM’s compact primary LDOs with highly stable output voltage stability

In recent years, the evolution of ADAS (Advanced Driver Assistance System) and other safety measures is requiring improved reliability for systems that supply power to these applications. As a result, redundant power supplies that can continue to operate core functions (sub-MCUs) even in the event of a main system malfunction are being increasingly incorporated in automotive power supply system. And as redundant power supply circuits are added to conventional systems, they must necessarily be space-saving and consume low power. ROHM's new products can be used as primary power supplies by taking advantage of original power supply technology accumulated over many years.

The compact (2.9mm × 2.8mm) BD7xxL05G-C series meets key requirements for building redundant power supplies by providing high withstand voltage (Max.=45V) with low current consumption (6.0µA typ.). At the same time, leveraging ROHM’s strengths in analogue technology ensures stable output voltage even during steep battery voltage fluctuations. Unlike standard products with an overshoot of almost 1.3V that requires a large output capacitor to prevent the rated voltage of downstream devices such as sub-MCUs from being exceeded, ROHM LDOs limit voltage overshoot to just 0.1V, supporting much smaller output capacitors. Together with elimination of voltage clamping diode, this reduces board area by approximately 29% over general solutions while minimizing the number of additional circuits needed to configure redundant power supplies. High resistance to disturbance noise is also achieved (shown to eliminate output voltage fluctuation at all frequencies during ISO 11452-2 antenna irradiation testing), reducing the design load for noise countermeasures.

Going forward, ROHM will continue to contribute to improving automotive reliability by developing products utilising its strengths in analogue and other technologies.

Product lineup

The new BD7xxL05G-C series meets basic requirements, such as a compact size, support for 125°C (Ambient Temperature) operation, qualification under the AEC-Q100 automotive reliability standard, and low current consumption demanded of automotive redundant power supplies. What’s more, they can be used as primary power supplies (45V rated input voltage) despite their small size, with a lineup that makes it possible to select the ideal solution according to the downstream device (i.e., sensor, MCU).

These LDOs are also highly resistant to disturbance noise, suppressing output voltage fluctuations to less than 50mV (<±1%) over the entire frequency band under ISO 11452-2 antenna irradiation testing, reducing the number of man-hours required for noise countermeasures.

Application examples

In addition to redundant power supplies, the space-saving low power consumption design makes them ideal for applications that operate when the engine is stopped.

Brake Systems, Body Control Modules,

Electric Power Steering, Battery Control Units,

ADAS ECUs, Real-Time Clocks,

Drive Recorders, Door Handle Modules