Automotive DC motor pre-driver from ST simplifies EMI optimisation and saves power
The L99H92 automotive gate driver from ST 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 minimise 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 minimise 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.
