Automotive electric power steering block diagram

Electric power steering (EPS) systems are gaining more and more momentum in modern vehicles, from compact cars to heavier class C/D/E and SUV segments. By providing power assistance and consuming energy only when the steering wheel is turned by the driver, EPS produces significantly less CO2 than conventional belt driven or even modern electro-hydraulic power steering system (EHPS).

Using accurate data on steering column torque and angle and rotor position from our magnetoresistive (MR) sensors, our MOSFETs enable efficient inverter and failsafe power stage design. Also, families of CAN and FlexRay transceivers ensure robust and instant communication between the EPS and the rest of the vehicle.

NXP actively supports the development of next generation active steering and steer-by-wire systems, as well as the integration of the steering function into the overall vehicle control system.

Driving diverse loads
The range of load currents in power steering systems is extensive. They can be a few mA for driving LEDs in the instrument cluster, up to more than 100 A for driving the electric motor. NXP offers discrete solutions such as small-signal MOSFETs, low VCEsat (BISS) transistors, constant current sources (PSSI), high-side loadswitches (PBLS family) and logic devices for small and medium loads such as warning lamps or relays ensuring the safety switch function.

Our Power MOSFET devices in advanced TrenchMOS technology drive the motor, typically a 3-phase brushless DC motor. High current Power MOSFETs are also perfect for an under-the-hood approach to the safety switch which, under fault conditions, separates the 3-phases of the steering motor from the inverter. For such thermally dynamic applications we provide enhanced D2PAK with appropriate mechanical and thermal ruggedness for drain-currents far beyond 100 A. With additional source pins and thickened bond wires in our new 7-pin D2PAK, currents of in excess of 300 A can be achieved.

Providing cost-effective solutions, all of these products share certain characteristics, such as low conduction losses and innovative packages, that save board space.

In-vehicle communication
For all networking protocols, we offer standalone CAN and FlexRay transceivers, with advanced functionality such as failure management and power saving. We also deliver highly integrated in-vehicle-networking products including system basis chip (SBC) families. The SBCs combine one or several bus transceivers, voltage regulators, I/O pins and the option of a watchdog in a single IC. They offer advanced low power mode control and smart fail-safe behavior. Pin compatible family devices with different transceiver options support scalable platforms by simply changing the population of the PCB.

Magnetoresistive and temperature sensors
NXP’s MR angular sensors are ideal for gathering the necessary torque, angle and position information to control modern EPS applications. Each device consists of a magneto-resistive element equipped with two independent MR sensor bridges and two instrumentation amplifiers with temperature compensation. Delivering an output signal virtually independent of magnet tolerances, magnet temperature coefficients, magnet-sensor distance and positioning tolerances, MR sensors guarantee reliability and simplify your manufacturing process.

Our silicon-based temperature sensors ensure highly accurate measurement with a long operating life. The KTY series can be used in systems for overheating protection and temperature monitoring to reduce the PWM control.

I/O protection
NXP offers a series of ESD protection devices out of the PESD family, specifically designed to protect automotive networks.

For robust reverse polarity protection NXP offers solutions based on either low ohmic Power MOSFET devices in advanced TrenchMOS technology or Schottky rectifier in an advanced clip bond technology (PMEG family) in SOD123W and SOD128 packages enabling full performance with small form factor.

Glue logic
Beside a complete portfolio of standard logic products with different supply voltage range and speed in innovative packages, NXP offers dedicated devices such as low ohmic analog switches, analog and digital multiplexers and I/O expansion devices for cost optimized EPS solutions.

Discretes
NXP, as a leading supplier of small-signal discretes we sell a variety of products into the power steering application space. The product innovation is based on three key innovation drivers: improve power efficiency; offer system protection solutions and to provide miniaturization and integration to simplify design and reduce costs. We lead the way with power-efficient low VCEsat (BISS) transistors and low VF (MEGA) Schottky rectifiers, and offer dedicated protection solutions for automotive networking.

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