100V MOSFETs reduce EMI in automotive hybrid powertrains

Three automotive grade, 100V, 4A half-bridge n-channel MOSFET drivers from Renesas enables high current DC/DC conversion with adjustable deadtime.

The ISL784x4 family features three devices, the ISL78424 and ISL78444 with single tri-level PWM input for controlling both gate drivers, and the ISL78434, which has dual independent inputs that separately control the high-side and low-side drivers.

The ISL784x4 half-bridge n-MOSFET drivers complement Renesas’ ISL78224 four-phase bi-directional controller, enabling it to provide up to 3kW of power and greater than 95 per cent efficiency in 12 to 48V converters used in mild hybrid vehicles. The ISL784x4 drivers are also well suited for 12 to 24V bi-directional DC/DC converters, as well as other high current buck or boost applications.

The ISL784x4 drivers simplify driving high-current MOSFETs by offering independent sourcing and sinking MOSFET gate drive pins. This makes it easy for designers to use external gate resistors to tune the slew rate of the rising and falling DC/DC switch node transitions, thereby reducing EMI, says the company. The ISL784x4 also provide adaptive deadtime control to ensure accurate break-before-make switching operations that prevent shoot-through current that would occur if both DC/DC converter switches were allowed to close simultaneously. Additionally, the ISL78424 and ISL78434’s adaptive deadtime function is able to sense at the gate of the MOSFETs, eliminating potential errors introduced by voltage drops across the external gate resistors controlling the switching node slew rate.

The ISL784x4 drivers are a great fit in high current DC/DC applications like the 12 to 48V converter for 48V mild hybrids. They improve efficiency by delivering robust gate drive with 3A peak sourcing current and 4A peak sinking current. Strong gate drive allows them to rapidly switch high current MOSFETs with large gate capacitance, which reduces switching losses, observes Renesas. The half-bridge MOSFET drivers’ adaptive dead time control minimises excess dead time to reduce conduction losses and further increase DC/DC conversion efficiency. In addition, the ISL784x4 drivers offer voltage ratings that are suitable for 48V automotive systems with the switching node tolerating 70V DC and up to 86V for infrequent transients. Similarly, the high-side driver’s bootstrap node can tolerate 86V DC and up to 100V during transients.

The AEC-Q100 Grade-1 qualified devices are specified for operation from -40 to +140 degrees C

The ISL78424 and ISL78444 using tri-level PWM signals can be combined with the ISL78224 four-phase bi-directional, synchronous PWM controller to perform power conversion between 12 and 48V buses in 48V mild hybrid vehicles. Designers can add a Renesas RH850 microcontroller to provide ASIL safety monitoring, system control and vehicle communication. The ISL78424 and ISL78444 can also be combined with the ISL78225 four-phase controller or ISL78220 six-phase controller to create an automotive audio amplifier power supply.

The ISL78424, ISL78434, and ISL78444 half bridge drivers and evaluation boards are available now.


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