Automotive 3-phase motor gate driver

Automotive 3-phase motor gate driver unit for BLDC motors


Designed to be the ST’s first gate driver unit (GDU) for automotive to support up to 48 V battery applications. Fully compliant with the ISO 26262 ASIL-D standard, the device guarantees high-performance control of six N-channel FETs to drive the brushless motors in fans, pump controls, brake boosters, steering systems, and transmissions of hybrid and energy-efficient vehicles.

The L9908 is a gate driver unit (GDU) able to control 6 N-channel FETs for brushless motors in automotive applications up to 48 V batteries. Each one of the 3 half-bridge driver channels (HS/LS couples) can be independently configured.

Through 6 dedicated parallel inputs, the pre-driver stages can be controlled independently supporting duty cycle operations from 0% to 100% and allowing to implement all kinds of electric motor control strategies. A dedicated combination of regulators, charge pumps and bootstrap circuits makes the L9908 suitable for use in passenger, commercial, hybrid and energy-efficient vehicles.

To guarantee high-performance control of brushless motors, the L9908 is equipped with 3 independent high-accuracy current monitor channels with SPI-configurable input differential voltage ranges for ground referenced current measurements.

A 32-bit out-of-frame SPI slave interface is implemented for communication up to 10 MHz between the L9908 and the microcontroller. It allows advanced control and diagnostics of the device and enables generic software development. Moreover, the L9908 implements diagnostics on external and internal supplies, ground level, and internal temperature.

Key features

  • VDH motor supply voltage range from 4.5 to 75 V for working in single (12 V systems), double (24 V systems) and 48 V battery applications
  • 6 separate N-channel FET pre-drivers (dedicated source connection to each FET, the device can withstand -14 V to 95 V on motor connection pins, 0% to 100% duty cycle operation support, dedicated PWM input pin for each gate driver)
  • 3 differential high-accuracy current monitors for ground referred current measurements
  • 3 real-time phase voltage monitor channels
  • Protection and supervision features including current monitor, open-load and overcurrent, thermal warning and thermal shutdown, etc.
  • 32-bit, 10 MHz SPI interface with 5-bit CRC and 1-bit frame counter for internal settings, self-test and full protection and diagnostics (SPI programmable diagnostics and protection in on-state, SPI programmable dead time protection, SPI programmable diagnostic and protection in off-state, over-temperature diagnostic and protection, SPI readable Tj measurement, ground loss diagnostics, over-voltage and under-voltage diagnostics on power supply pins and FET driver, SPI Window Watchdog, fault status flag output, etc…)
  • Full ISO 26262 compliant and ASIL-D systems ready

Application examples

electronic power steering eps Electronic power steering (EPS)
hvac heating ventilation air conditioning HVAC (Heating, Ventilation, and Air Conditioning) blowers and fans
engine cooling fans Engine cooling fans
electronic brake booster Electronic brake booster
automotive EWP, EFP, and EOP

Recommended resources

aek mot 3p99081

Part of the AutoDevKit ecosystem, the AEK-MOT-3P99081 evaluation board is a standalone motor drive controllable via CAN by a host microcontroller. Example code is also available.

aek mot 3p9908m

Part of the AutoDevKit ecosystem, the AEK-MOT-3P9908M evaluation board is a standalone motor drive controllable via CAN by a host microcontroller. The package includes a 65W BLDC motor with Hall sensors. Example code is also available.

pdf automotive 3 phase motor gate driver unit

This application note explains the various features and functions of the L9908 GDU. In addition to PCB layout considerations, there is information on evaluating your design using the L9908 development platform and using two L9908 GDUs in a dual device system.

news automotive gate driver

This press release describes the innovative features of the L9908 gate driver unit (GDU) and how its flexible input and output channels fulfil numerous applications in conventional and hybrid/electric vehicles.