Application

Without reliably powering a functional safety microcontroller during a catastrophic system failure, the microcontroller is not effective at reducing risk. This leads to the development of power management devices which contain design elements that enable the PMIC to fail-safe in multiple potential failure scenarios.

However, with increasingly higher power requirements of functional safety microcontrollers, there is a growing need for higher compute-core power delivery, often demanding more current than modern multirail power management devices can offer on a single rail. Instead, by using the PMIC buck-boost preregulator to power an automotive-qualified, high-efficiency buck converter, greater current can be delivered to the core of the functional safety microcontroller, enabling a system that can meet ISO26262 ASIL-D standards.

The TPS653860-Q1 is the latest offering from TI for functional safety PMICs and includes two external voltage monitors that can monitor external voltage rails, such as the core rail of the functional safety microcontroller. The microcontroller is powered by a high-efficiency buck converter. As the device is intended for use in safety-relevant applications, additional monitoring and protecting features are included that improve the diagnostic coverage and decrease the undetected fault rate.

Since this system is always connected to the battery of the vehicle and can be always powered on, low quiescent current is required. TI automotive buck switching regulators are an option for microcontroller rails that can always be powered. Some bucks feature industry-leading low quiescent currents, reaching as low as a few microamperes.

Efficiency is a key performance characteristic for evaluating the application effectiveness of a system. Most of the lost energy in electrical systems is converted into heat. Several devices under load in a constrained space can lead to self-heating which can result in thermal stress on a system. This results in greater thermal performance requirements of the devices in a system. In automotive settings, this is a concern as more automotive electrical systems have higher power requirements every year and automotive use cases can be subject to extreme ambient temperatures.

Any integrated circuit can fail to perform if the thermal conditions of the application cause the system to enter thermal shutdown. TI offers power management devices in AEC-Q100 grade 1 and grade 0 variants. Normal operation is from -40°C to +150°C and -40°C to +175°C, respectively. Some buck offerings from TI are qualified at AEC-Q100 grade 1, but are also verified in testing to operate from -40°C to +175°C.