L9908 Gate Driver: One chip for all kinds of automotive motor control

The L9908 high-integration automotive specification three-phase gate driver unit (GDU), ST's star product in brushless motor-related applications, is ST's first GDU to support 48V batteries, meeting the latest power requirements arising from the popularity of hybrid and new-energy vehicles.

_L9908

The L9908 can control six N-channel FETs to drive brushless motors in electric power steering systems, brake boosters, fans, pump motors, transmissions, etc. and is fully compliant with the automotive functional safety ISO26262ASIL-D standard.

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48 Volt Battery

When developing new applications, engineers need to invest heavily in devices, tools, and other aspects. 48V systems have become self-evidently important in automobiles. Larger batteries help to "save fuel, reduce emissions and increase power".

Several manufacturers with a voice in the battery space also emphasize the importance of 48V batteries, but there are challenges in switching from legacy power systems to 48V. the L9908 can support newer designs based on previous generations for a smooth transition.

The L9908 is the next generation of the L9907, supporting 3.3V and 5V logic and supply voltage ranges down to 4.5V. Both the L9907 and L9908 are AEC-Q100 certified, and the L9908 is ASIL-D compliant for additional applications.

3 Current Sensors Based on Analog Topology

Engineers are always looking for more cost-effective solutions, and analog sensing is the way to go. However, the analog topology has a poorer signal-to-noise ratio and longer output stabilization time than the floating topology, so it may affect the use of torque and complex algorithms.

However, customers need more powerful motor control for performance, and drivers want smooth, vibration-free steering. So, despite the limitations of traditional analog topologies, designers must also find ways to improve performance.

▲ Consumers demand smoother, smoother steering

The L9908 offers a solution by coupling an analog topology with a digital SPI line and three sensors. The sensors provide greater flexibility and more data, and developers can employ magnetic field control (FOC) techniques to improve overall performance and efficiency. Sophisticated algorithms can help create more advanced steering columns without compromising the cost effectiveness of the overall solution.

What car manufacturers care about most

Safety

Automotive requirements for gate drivers have changed dramatically over the past few years. ISOs require GDUs that support 48V applications to be able to handle 75V supply voltages. The reason behind these changes is that smart and electric vehicles require stricter safety regulations to protect consumers.

Therefore, the L9908 provides new diagnostic and protection features using a 32-bit SPI interface. safety features of the L9908 include SPI set dead time insertion and straight through short circuit diagnostic protection; open load detection, short to ground diagnostics, short to battery diagnostics; and the ability to set temperature warnings and read junction temperature measurements via the SPI bus.

Simplifies Prototyping

The L9908 ushers in a new era of automotive applications. To help engineers catch up with application development trends, ST offers a variety of development boards with the L9908 and SPC560P.

development boards with the L9908 and SPC560P

▲ AEK-MOT-3P99081

The AEK-MOT-3P99081 works to help engineers prototype faster. autoDevKit provides a way to complete proof-of-concept in minutes. The solution comes with a demo using the L9908 to drive a BLDC motor with a Hall sensor, and ST also offers the kit AEK-MOT-3P9908M with development board and motor to further speed up development.

Many ways to play with the L9908 in automotive motor control

The highly integrated, flexible and accurate L9908 simplifies design, saves space and improves control accuracy in applications such as low-pressure liquid pumps, air pumps and blowers for ventilation and cooling systems, and power seat controls. The driver can also be used to design power motor inverters for light-hybrid vehicles (ICE) and 48V pure electric mobility vehicles.

48V inverter reference design system block diagram

▲ 48V inverter reference design system block diagram

ST, in conjunction with the Greater Bay Area Institute for Integrated Circuits and Systems Applications (GIICS), has developed a 48V inverter reference design based on ST's automotive-grade chip application solution, which includes an MCU (SPC58NN), SBC (L9396), Pre-Driver (L9908), analog chip, and logic protection chip.

The L9908 can also be used for safety systems such as AEB and advanced electric power steering , simplifying the ISO 26262 certification process. The following EPS demonstration solution consists of the ST automotive-grade 32-bit PowerPC architecture microprocessor SPC560P50, L9908 and automotive-grade MOS. The solution is suitable for 12V, 24V and 48V systems, and also has the corresponding diagnostic and protection functions.

Block diagram of brushless motor universal system

▲ Block diagram of brushless motor universal system

In single battery (12V), dual battery (24V) and 48V automotive battery systems, the L9908 offers high application flexibility because the motor power supply pins can withstand wide voltages from 4.5V to 75V and the motor connection pins can withstand voltages from -14V to 95V. The on-chip logic circuitry uses an internal 3.3V supply and the digital I/O ports are compatible with both 3.3V and 5V logic levels.

✦✦ Learn more about the L9908

✦✦ Get the AEK-MOT-3P99081 Development Board

✦✦ Explore the AEK-MOT-3P9908M

►Scenario Application Diagram

Scenario Application Diagram

►Core Technology Advantages

The L9908 highly integrated automotive specification three-phase gate drive unit (GDU), ST's star product in brushless motor-related applications, is ST's first GDU to support 48V batteries, meeting the latest power requirements arising from the popularity of hybrid and new energy vehicles. It supports 12V, 24V or 48V automotive power systems with flexible input and output channels for a variety of applications in both conventional fuel vehicles and hybrid/electric new energy vehicles.

► Solution Specifications