System power IC aids automotive functional safety

December 16, 2015 // By Graham Prophet
A general-purpose power control chip from Toshiba provides the highest levels of functional safety to enable car designs to meet ASIL-D requirements

With multiple outputs and functional safety circuits for automotive applications, the TB9044FNG is housed in an HTSSOP48-P-300-0.50 package measuring 6.1 by 12.5 x 1.0 mm. Safety-critical automotive systems, such as electric power steering (EPS) and braking, are required to meet the requirements of ASIL-D, the highest automotive safety integrity level prescribed in the ISO 26262 functional safety standards.

The IC integrates various failure detection functions, such as a high-voltage and low-voltage detection and overheat detection of power supply circuit to monitor against the IC’s own failure, and a watchdog timer to monitor failure detection of the external MCU. An initial diagnosis circuit to detect latent faults in the failure detection circuits is also incorporated to secure higher functional safety.

The IC generates a 6V output from a high efficiency buck-boost DC-DC converter. In order to avoid problems following a voltage drop during cranking, the low side operating voltage range is improved down to 2.7V (min.) with battery operation.

Toshiba has carried out a range of functional safety analyses to simulate system failures and will provide its customers with documentation, such as functional safety FMEDA, to support overall safety analysis and design.

The IC incorporates four series power supply output circuits receiving the 6V input generated by the DC-DC converter. It also incorporates an output circuit with a 5V constant voltage (current capacity of 400 mA) for the microcomputer, and three circuits with 5V constant voltage output (current capacity of 100 mA) for sensors and other interfaces. Each of them can output a voltage independently.

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