Integration Can Simplify Motor Development Process

July 17, 2016

Terry Costlow

TI claims its new resolver sensor interface can reduce complexity in the design of the growing number of electric motors in vehicles.

Texas Instruments aims to simplify the design process for the growing number of electric motors used in hybrids and in applications like electric power steering. TI recently unveiled a resolver sensor interface that saves space and provides accuracy that can smooth performance in stop start systems.

The device includes an integrated power supply, exciter amplifier and functional safety features. It simultaneously excites the resolver sensor coil and calculates the angle and velocity of a rotating motor shaft without the external components required by competitive solutions. It’s designed for harsh environments like powertrains.

“This reduces complications in design,” said Amanda Weise, Product Marketing Engineer, Mixed Signal Automotive, at TI. “The resolver sensor interface is not housed in the motor, it sits on a board with the microcontroller and motor driver. Six wires are all that are needed to connect it.”

The PGA411-Q1’s architecture improves system accuracy and stability for systems like hybrid electric vehicle/electric vehicle (HEV/EV) traction inverters, electric power steering and integrated start-stop generators. Integrating components can cut printed circuit board space in half by eliminating at least 10 external and passive components.

“Most solutions us an analog to digital convert, we don’t do a conversion,” Weise said. “We keep analog signals in an analog domain as much as possible. Op amps have adjustable gain; our accuracy is not impacted by the environment.”

The device improves reliability by separating the high-current and high-voltage blocks from sensitive components like the analog front end, which are highly susceptible to damage. Weise said the part’s accuracy could help suppliers reduce the jerkiness that’s plagued many stop start systems.

“For electric power steering and stop-start, you need angle and velocity information,” she said. “For stop-start, the system has to figure out where the motor stopped. To eliminate a jolt when the engine restarts, we provide instantaneous information for exactly where it stopped so the car can pick up where it left off.”

In a related move, TI also unveiled an integrated three-phase brushless DC gate driver, the DRV8305-Q1. It includes a 3.3V or 5V linear regulator, three current-sense amplifiers and a smart gate-drive architecture that allows easy optimization of MOSFET electromagnetic compliance. It eliminates up to 20 external components and operates down to 4.4 V to support start-stop functionality.