Compact primary LDOs ideal for redundant power supplies

ROHM has developed primary LDO regulators – BD7xxL05G-C series (BD725L05G-C, BD730L05G-C, BD733L05G-C, and BD750L05G-C) providing a rated input voltage of 45V and 50mA output current optimised for redundant power supplies that are being increasingly employed in automotive applications to enhance the reliability of vehicle power systems.

In recent years, the evolution of ADAS and other safety measures needs improved reliability for systems that supply power to these applications. Consequently, redundant power supplies that can continue to operate core functions (sub-MCUs) even in the event of a main system malfunction are increasingly included in automotive power supply systems. And as redundant power supply circuits are added to conventional systems, they must be space-saving and consume low power. The company's new products can be employed as primary power supplies utilising original power supply technology accumulated over many years.

The compact (2.9mm × 2.8mm) BD7xxL05G-C series meets key necessities for building redundant power supplies by supplying high withstand voltage (Max =45V) with low current consumption (6µA typ). At the same time, leveraging the company's strengths in analog technology provides stable output voltage even during steep battery voltage fluctuations. Unlike standard products with an overshoot of almost 1.3V that needs a large output capacitor to stop the rated voltage of downstream devices such as sub-MCUs from being exceeded, the LDOs limit voltage overshoot to only 0.1V, supporting much smaller output capacitors. Eradicating the voltage clamping diode decreases board area by approximately 29% over general solutions while minimising the extra circuits needed to configure redundant power supplies. High resistance to disturbance noise is also achieved (shown to stop output voltage fluctuation at all frequencies during ISO 11452-2 antenna irradiation testing), reducing the design load for noise countermeasures.

The new BD7xxL05G-C series satisfies basic requirements, such as compact size, support for 125C (Ambient Temperature) operation, qualification under the AEC-Q100 automotive reliability standard, and low current consumption demanded of automotive redundant power supplies. Moreover, they can be employed 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, such as a sensor or MCU.

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

As well as redundant power supplies, the space-saving low power consumption design makes them ideal for brake systems, body control modules, electric power steering, battery control units, ADAS ECUs, real-time clocks, drive recorders, and door handle module.