News Article

ROHM Power Supply Monitoring IC With Built-In Self-Diagnostic Function


ROHM recently announced the availability of a power supply monitoring IC, the BD39040MUF-C, with BIST (Built-In Self Test) that supports functional safety. This IC is ideal for automotive application power supply systems requiring fail-safe measures such as electric power steering as well as sensors and cameras for autonomous driving and ADAS.

Fig. 1

Rapid advancements in ADAS and automated driving in the automotive sector have spurred demand for functions such as collision prevention and lane assist that reduce the risk of accidents. Accordingly, product development for mounted semiconductors has to take into account how to ensure functional safety (fail-safe) in the event of failure considering self-diagnostic and other functions.


In 2017 ROHM developed an LCD chipset which supported functional safety and comprised of LCD drivers and power supply ICs ahead of the industry. In 2018 the company acquired certification of the development process under the international functional safety development standard ISO26262. At this time, when considering the safety and redundancy of systems, incorporating various self-test and monitoring functions ROHM created the industry's first power supply monitoring IC with built-in self-diagnostic function that makes it easy to add functional safety to existing systems.

The BD39040MUF-C is a power monitoring IC that provides monitoring functions required for functional safety in the power supply systems of ADAS sensor modules. In addition to voltage monitoring functions (Power Good, reset) and a watchdog timer for monitoring the ECU essential for functional safety, ROHM's power supply monitoring IC is the first in the industry to introduce a self-diagnostic function. By utilizing original technology, this IC makes it possible to detect potential failure of the power supply IC itself without affecting existing systems. The integration of these functions into a compact 3mm square package makes it ideal for ADAS applications demanding high miniaturization.

Availability: Now (samples), August 2019 (OEM quantities)

Key Features

The BD39040MUF-C is the first power supply monitoring IC in the industry
to include a self-diagnostic function along with additional features
that make it ideal for functional safety systems required for ADAS and
automated driving.

1. Self-diagnostic function provides the reliability needed for functional safety

For functional safety, to clear the highest safety requirement level
(ASIL) it is necessary to detect potential failures of the power supply
monitoring function itself. For example, in the case a failure occurs
when a monitoring function (i.e. overvoltage) cannot detect an
abnormality, it becomes a hidden fault that masks the breakdown,
creating a dangerous situation.

In order to overcome this, the BD39040MUF-C with self-diagnostic
function utilizes original circuit technology that enables it to detect
potential failures beforehand. Both the reference voltage and oscillator
circuits are multiplexed to enable continuous mutual monitoring between
systems in order to improve safety during normal operation.

Fig. 3

2. Provides flexible support for existing systems

The BD39040MUF-C easily supports functional safety in existing systems
without any changes of power supply sequences. Additionally, the
watchdog timer for ECU can be adjusted via external resistance and the
effective monitoring timing arbitrarily set ON/OFF. Furthermore, the IC
is offered in a compact 3mm square package ideal for ADAS applications
requiring smaller form factor. This addresses the need for more compact
safe driving support modules in ADAS and automated driving systems that
demand functional safety.

3. Integrates various monitoring functions required by automotive power supplies and ECUs

The BD39040MUF-C incorporates a range of monitoring functions, including
overvoltage and undervoltage monitoring (Power Good) required for power
supplies, and watchdog timer and reset functions demanded by ECUs.
Among these, the watchdog timer is a window-type that monitors whether
the ECU is stuck in a loop within a programmable timeout period.

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