St develops 8-channel gate drivers to reduce bill of material costs for automotive motors
Date：January 27, 2025 Views：36
STMicroelectronics (ST) has developed the 8-channel gate driver L99MH98 to reduce the bill of material cost of automotive motors.
Photo credit: ST
The 8-channel predriver uses a patented approach to build a motor driver that requires no sensing resistance, thereby reducing power dissipation and the bill of materials for power seats, sunroofs, window lifts, sliding doors, trunk and tailgate.The L99MH98 can drive four external full axle, eight half-axle, or a single high/low side power supply mechanism such as seat position adjusters, window lifters, sunroofs, pumps, seat belt pretensioner, and other actuators. The L99MH98 can also drive resistive loads, such as heaters, and the internal circuit contains a charge pump whose output controls the reverse battery protection MOSFETs.
While drivers can control both logic level and standard level MOSFETs, the extended gate current capability (programmable up to 120mA) allows driving a large number of external MOSFETs. Three-stage grid control applies the grid signal in three steps to help minimize electromagnetic radiation.
The device feeds the drain-source voltage (VDS) of each MOSFET to an analog-to-digital converter (ADC) and replaces the sensing resistance with indirect current measurement. This patented technology calculates the drain current in each MOSFET by combining the measured VDS with the RDS (on) predicted using the sensing temperature.
The system is calibrated at the time of manufacture to find a nominal RDS (on) value, which can be predicted using the resistance and temperature curves of the MOSFETs.
Its 24-bit serial peripheral interface (SPI) is used to configure and control eight half-bridges or four H-bridges. The SPI status register provides advanced diagnostic information such as power supply voltage monitoring, charge pump voltage monitoring, temperature warning, and overheat shutdown.
Another feature (also patented) is the programmable multiple fault protection feature, which improves reliability by shutting down the bridge individually to prevent failure while allowing unaffected Bridges to operate properly. Multiple fault protection detects faults, including power overvoltage, high end overvoltage/undervoltage, heat warning, charge pump failure, VDS monitoring failure, and selectively turns off diagnostic, watchdog, and charge pump functions depending on the type of failure.
The 8-channel gate driver is AEC-Q100 compliant and ISO 26262 compliant for functional safety applications up to Safety Integrity Level (ASIL) B.
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