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11-28-2018

Renesas 100V Half-Bridge Drivers Safely Drive MOSFETs for Bidirectional Controller in 12V-48V Automotive Hybrid Powertrains

Renesas » ISL78424, ISL78434, ISL78444

Advanced ISL784x4 MOSFET Driver Family Enables High Current DC/DC Conversion with Adjustable Dead Time and Maximum Efficiency

Renesas Electronics announced a new family of automotive-grade 100 V, 4 A half-bridge N-channel MOSFET drivers. 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 the ISL78224 4-phase bidirectional controller, enabling it to provide up to 3 kW of power and greater than 95 percent efficiency in 12 V-48 V converters used in mild hybrid vehicles. The ISL784x4 drivers are also well suited for 12V-24V bidirectional DC/DC converters, as well as other high current buck or boost applications.

Renesas - ISL78424, ISL78434, ISL78444

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 are a great fit in high current DC/DC applications like the 12-48 V converter for 48 V mild hybrids. They improve efficiency by delivering robust gate drive with 3 A peak sourcing current and 4 A 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 minimizes 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 48 V automotive systems with the switching node tolerating 70 V DC and up to 86 V for infrequent transients. Similarly, the high-side driver’s bootstrap node can tolerate 86 V DC and up to 100 V during transients.

Key Features of ISL78424, ISL78434 and ISL78444

  • 3 A sourcing / 4 A 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 8 V to 18 V
  • On-chip 3 Ω 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 °C 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 12 V and 48 V buses in 48 V 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 4-phase controller or ISL78220 6-phase controller to create an automotive audio amplifier power supply.

Pricing and Availability

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 USD in 1k quantities.

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