Automotive DC motor pre-driver from STMicroelectronics simplifies EMI optimization and saves power

The L99H92 automotive gate driver from STMicroelectronics provides an SPI port for programming and diagnostics, a charge pump, protective features, and two additional current-sense amplifiers for system monitoring.

Containing two high-side and two low-side drivers, the L99H92 can control a single H-bridge powering one bidirectional DC motor or two half bridges for two unidirectional motors. Typical applications for the highly integrated and easily configurable driver include electric sunroof, window lift, powered trunk, sliding doors, and seat-belt pre-tensioners.

The charge pump powers the high-side drivers to maintain correct operation as the vehicle battery voltage fluctuates, enabling the outputs to function with a supply as low as 5.41V. The charge-pump output is also available at an external pin to control a MOSFET for reverse-battery protection.

The gate-driving current is programmed through the SPI port, allowing slew-rate control to minimize electromagnetic emissions and thermal dissipation. Programming the current saves up to four external discrete components per MOSFET, typically needed for slew-rate setting with conventional drivers. The maximum drive current of 170mA gives designers flexibility to use the driver with a wide variety of external MOSFETs, including high-power devices with large gate capacitance.

With many features for system protection and diagnostics, the L99H92 is built for reliability and safety. There is overcurrent protection with a programmable threshold, detected by monitoring the MOSFET drain current. Also, cross-conduction protection with programmable dead time ensures safety and efficiency. Additional protection includes overtemperature early warning and shutdown, overvoltage and undervoltage protection on analog and digital power supply inputs, and open-load and output short-circuit detection in off-state diagnostic mode.

A fail-safe input can turn off all MOSFETs instantaneously and a dedicated diagnostic pin provides immediate fault warning without waiting for periodic SPI transfers.

Additionally, two current-sense amplifiers are integrated for system-status monitoring, helping minimize the bill of materials. Suitable for high-side, low-side, and inline sensing, the amplifiers have independently programmable gain, low offset, and low thermal drift. They can be independently disabled to reduce current consumption when unused.

Sliding doors

Sun-roofs

Window Lifters

Parking brake

Description

The L99H92 is designed to drive 4 external N-channel MOSFET transistors in single H-bridge or dual independent half bridge configuration for DC-motor control in automotive applications. Two free configurable current sense amplifiers are integrated.

The device has a low power mode (standby mode) where the current consumption is less than 5 µA.

Programmable gate driving current allows minimizing EMI. Each gate driver monitors independently its external MOSFET drain-source voltage for fault conditions.

Programmable cross current protection time avoids concurrency of high side and low side activation for each half bridge.

Two off-state diagnostic comparators detect potential short to ground, short to battery or open load conditions.

The integrated standard serial peripheral interface (SPI) controls the device and provides diagnostic information. An additional DIAGN output pin alerts the microcontrollers of a fault occurred into the device faster than the SPI communication.

The L99H92 device implements diagnostic and protection features such as supply voltage monitoring, charge pump voltage monitoring, overcurrent protection, temperature warning and overtemperature shutdown.

The devices are hosted in a TQFP32 and a QFN32 package both with exposed pad. QFN32 has wettable flanks for easy visual inspection of the solder joint.

• All features

  • AEC-Q100 qualified
  • RoHs compliant device
  • Power supply operating range from 4.51 V to 28 V (gate drivers operative from 5.41 V)
  • 3.3 V/5 V compatible I/Os
  • All pins linked to the microcontroller, fail-safe input and VDD are made tolerant to battery exposure
  • Dual half-bridge driver compatible with standard level threshold NMOSFETs
  • Configurable full-bridge or dual independent half-bridges control
    • Programmable recirculation path in case of full-bridge control
  • Dual stage charge pump supporting 100% PWM duty cycle down to 5.41 V battery voltage
    • High and low side minimum V_GS=6.2 V @ VDH=5.5 V and charge pump load current (I_CPLOAD) equal to 5 mA
    • High and low side minimum V_GS=8.2 V @ VDH≥8 V and charge pump load current (I_CPLOAD) equal to 10 mA
  • Charge pump output available for driving an external reverse battery NMOSFET protection
  • Programmable gate driving current (up to 170 mA) for output voltage slew rate control

  • Programmable drain-source monitoring for overcurrent protection and programmable cross-current protection time (dead-time)
  • Open load and output short circuit detection in off-state diagnostic mode
  • SPI for control and diagnosis (ST SPI 4.1)
  • Programmable diagnostic output
  • Two independent current sense amplifiers
    • Low offset with extremely low thermal drift
    • Suitable for high-side, in-line and low–side current sensing
    • Independently programmable gain (10x, 20x, 50x, 100x)
    • Analog output centered at V_DD/2 or VDD/22
  • Overtemperature prewarning and shutdown
  • Analog and digital power supply inputs over/undervoltage protections
  • Asynchronous and logic independent fail-safe input to switch off all the MOSFETs
  • Low quiescent current
  • Support for random HW faults up to ASIL B