With safety-critical automotive systems such as EPS now required to meet ASIL-D requirements [2], an industry standard designed to minimize the risk of system failures, it is vital for these devices to offer comprehensive redundancy and protection systems. The new TB9081FG integrates numerous protection functions, including three-phase pre-controller circuits [3], fail-safe relay pre-controller circuits [3], motor current detection circuits [4], and several additional fault detection circuits to detect latent faults. An initial diagnostic circuit to detect latent faults in the fault detection circuits has also been incorporated to provide even higher levels of functional safety.
Toshiba has conducted a series of functional safety analyses to simulate various system failures and provide customers with documentation, such as FMEDA [5], to support safety analysis and design. Built-in fail-safe pre-controller relay circuits manage the semiconductor relay between the motor and MOSFET (controller) and between the power supply side and the MOSFET (controller). The fail-safe pre-controller relay circuits have a total of five channels: three for the motor side and two for the power supply side. Both have dedicated input terminals, enabling independent control.
Housed in an LQFP64 package, the TB9081FG measures 12.0mm × 12.0mm × 1.6mm. The device will enter serial production in 2017, with samples available later in 2015.
Grades:
[1] Standards based on functional safety aim to minimize the risks resulting from system failures. ISO 26262 certification recognizes that the processes or products of an electrical and electronic (E/E) systems company for automotive applications meet the stringent criteria specified in the standard and provides third parties with an independent means of evaluating a potential supplier's capabilities.
[2] ASIL: Automotive Safety Integrity Level
[3] Pre-controllers for controlling the drive motor MOSFET
[4] Converts motor current to voltage and an MCU (Microcontroller Unit) output
[5] FMEDA: Failure Mode Effects and Diagnostics Analysis
