Compact primary LDOs maintain core functions in redundant power supplies
Primary LDO regulators have been developed by Rohm to maintain power for core functions even in the event of a vehicle system malfunction.
The BD7xxL05G-C series (BD725L05G-C, BD730L05G-C, BD733L05G-C, and BD750L05G-C) feature a rated input voltage of 45V and 50mA output current. They are optimised for redundant power supplies used in automotive applications to improve the reliability of vehicle power systems.
ADAS (advanced driver assistance systems) and other safety measures rely on systems and their power supplies. This has led to an increase in interest in redundant power supplies that can continue to operate core functions (sub-microcontrollers) even in the event of a main system malfunction. They are being increasingly incorporated in automotive power supply system but they must be designed for the limited space available and must consume low power.
Rohm conforms that the LDOs can be used as primary power supplies by taking advantage of original power supply technology accumulated over many years.
The compact BD7xxL05G-C series measures 2.9 x 2.8mm and meets key requirements for building redundant power supplies by providing high withstand voltage (max 45V) with low current consumption (6.0 microA typical). The LDOs also have stable output voltage even during steep battery voltage fluctuations. Unlike standard products with an overshoot of almost 1.3V that require a large output capacitor to prevent the rated voltage of downstream devices being exceeded, these LDOs limit voltage overshoot to just 0.1V, explained Rohm, and can therefore support much smaller output capacitors. Together with the elimination of voltage clamping diode, this reduces board area by approximately 29 per cent over general solutions while minimising 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 counter measures.
The BD7xxL05G-C series meets requirements such as support for 125 degrees C (ambient temperature) operation and are qualified to AEC-Q100.
They can also be used as primary power supplies (45V rated input voltage). They are highly resistant to disturbance noise, continued Rohm, suppressing output voltage fluctuations to less than 50mV (<± one per cent) over the entire frequency band under ISO 11452-2 antenna irradiation testing, reducing the number of man-hours required for noise counter measures.
The LDOs are designed for applications that operate when the engine is stopped. Examples include brake systems, body control modules, electric power steering, battery control units, ADAS engine control units (ECUs), real time clocks, drive recorders and door handle modules.
The LDOs are in mass production now and available from online distributors, Digi-Key, Mouser and Farnell with other distributors scheduled for later release.
