Brushed motor pre-driver IC for ASIL automotive applications

April 02, 2015 // By Graham Prophet
Enabling an automotive electric power steering system IC to meet ASIL-D standards, Toshiba Electronics Europe’s TB9057FG is a brushed motor pre-driver IC that provides enhanced functional safety and control for automotive applications such as electric power steering systems (EPS), to Automotive Safety Integrity Level D (ASIL-D).

The IC integrates a pre-driver circuit, dual motor current detection circuit that converts motor current to voltage and generates output to an MCU. It also integrates motor direction detection circuitry that detects whether external MOSFETs turn on or off normally, and outputs the direction information to MCU.

Various failure detection circuits such as VB under-voltage detection circuit, VDD under-voltage detection circuit, over temperature detection circuit, and short circuit detection circuitry that detects any short circuit between the drain and source of a driver (MOSFET), are also integrated into the IC. Motor current detection circuit, power supply PIN, and GND PIN are made redundant for greater robustness.

In order to accommodate the possibility of a voltage drop caused by cranking after idling reduction, the battery operation voltage range has been reduced to 5V (min.) compared to the 6V (min.) of the predecessor product.

Designers can set the system to respond to detected failures in one of two ways, using the input setting of the SEL pin. One setting uses this IC to stop the external MOSFET, the other switches to external control of the MOSFET using the MCU. Selection can be made according to the customer’s application or system, and reduces loads on the MCU. Toshiba has also carried out a range of functional safety analyses to simulate various system failures and will provide customers with documentation to support safety analysis and design.

In a LQFP48-P-0707-0.50C package measuring 9.0 x 9.0 x 1.6 mm, the IC operates over +5 to 21V and has an operating temperature range of -40°C to 125°C.

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