MOSFET driver enables high current conversion with adjustable deadtime

The ISL784x4 half-bridge N-MOSFET drivers complement the ISL78224 four-phase bidirectional controller, enabling it to provide up to three kilowatts of power and greater than 95% efficiency in 12V-48V converters used in mild hybrid vehicles. The ISL784x4 drivers are also well suited for 12-24V bidirectional 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 electromagnetic interference (EMI).

The ISL784x4 also provide adaptive dead-time 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 dead time 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 fit in high current DC/DC applications like the 12-48V converter for 48V mild hybrids. They improve efficiency by delivering robust gate drive with three amp peak sourcing current and four amp peak sinking current. Strong gate drive allows them to rapidly switch high current MOSFETs with large gate capacitance, which reduces switching losses. 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 ideal 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.

“Our new ISL784x4 half-bridge driver family is the first to combine gate-sensed adaptive dead time control with independent source/sink pins for slew-rate control,” said Akira Omichi, Vice President, Automotive System Project Management Division, Renesas Electronics. “Several best-in-class features enable the highly integrated ISL78424, ISL78434 and ISL78444 to outperform competitive half-bridge drivers, giving our customers the ultimate in performance and ease of use.”

Key Features of ISL78424, ISL78434 and ISL78444

• Thee amp sourcing / four amp sinking output current.
• Tri-level PWM input (ISL78424 and ISL78444).
• Independent HI/LI inputs (ISL78434).
• Separate source/sink pins at driver outputs (ISL78424 and ISL78434).
• Wide supply voltage range operates from eight to 18V.
• On-chip 3Ω bootstrap FET switch eliminates need for external Schottky diode.
• Adaptive dead time control and programmable dead time delay with single resistor.
• AEC-Q100 Grade-1 qualified and specified for operation from -40 to +140°C.

The ISL78424 and ISL78444 using tri-level PWM signals can be combined with the ISL78224 4-phase bidirectional, synchronous PWM controller to perform power conversion between 12V 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.

All three half-bridge drivers–ISL78424, ISL78434, and ISL78444–and evaluation boards are available now. Each device comes in a 14-lead HTSSOP package priced at $1.70 in 1k quantities.