Electric power steering brushless motor pre-driver aids ASIL rating

September 16, 2015 // By Graham Prophet
This brushless motor pre-driver IC for use in electric power steering (EPS) systems integrates enhanced fail safe and failure detection circuits to achieve a high level of functional safety.

Safety-critical automotive systems such as EPS must meet the requirements of ASIL-D (Automotive Safety Integrity Level), and offer comprehensive redundancy and protection systems. Toshiba’s TB9081FG integrates protection functions including 3-phase pre-driver circuits, fail-safe relay pre-driver circuits, motor current detection circuits, plus various additional failure detection circuits to detect latent faults. An initial diagnosis circuit to detect latent faults in the failure detection circuits is also incorporated to provide even higher levels of functional safety.

Toshiba has carried out a range of functional safety analyses to simulate various system failures and will provide customers with documentation, such as FMEDA (Failure Modes Effects and Diagnostics Analysis), to support safety analysis and design. Built-in fail-safe relay pre-driver circuits drive the semiconductor relay between the motor and MOSFET (driver) and between the power-supply side and MOSFET (driver). The fail-safe relay pre-driver circuits have a total of five channels, three for the motor side and two for the power-supply side. Both have dedicated input terminals, making independent control possible.

Housed in a LQFP64 package, the TB9081FG measures 12.0 × 12.0 × 1.6 mm. The device will be entering mass production in 2017, with samples available later in 2015.

Toshiba Electronics Europe; www.toshiba.semicon-storage.com