U3406

The U3406 is a 400V synchronous buck controller that regulates from high input voltage sources or input rails subject to high-voltage transients, minimizing the need for external surge suppression components. A 60ns high-side switch minimum on-time provides a large step-down ratio, enabling direct buck conversion from a 100V nominal input to low-voltage rails, reducing system complexity and solution cost. The device continues to operate with input voltages as low as 8.5V, allowing duty cycles approaching 100% when necessary, making it ideal for high-performance 100V battery automotive applications, advanced driver assistance systems (surround-view ECUs), and hybrid/electric vehicle systems. Forced PWM operation eliminates switching frequency variation to minimize EMI, while a user-selectable diode emulation mode reduces current consumption under light-load conditions. Cycle-by-cycle overcurrent protection is achieved by measuring the voltage drop across the low-side MOSFET or by using an optional current sense resistor. An adjustable switching frequency of up to 0.5MHz can be synchronized to an external clock source to eliminate beat frequencies in noise-sensitive applications. The U3406 employs voltage-mode control with line feedforward and drives external high-side and low-side N-channel power switches via 8.5V gate drivers compatible with standard-threshold MOSFETs. Adaptive timing gate drivers with 2A source and 2.5A sink current capability minimize body diode conduction during switching transitions, reducing switching losses and improving thermal performance when driving MOSFETs at high input voltages and high frequencies. The U3406 can be powered from the switching regulator output or another available supply to further improve efficiency. Additional features of the U3406 include configurable soft-start, an open-drain power-good monitor for fault reporting and output monitoring, monotonic startup into pre-biased loads, integrated VCC bias supply regulator and bootstrap diode, external supply tracking, a precision enable input with hysteresis for adjustable line UVLO, hiccup-mode overload protection, and thermal shutdown with auto-recovery. The controller is housed in a 10mm × 6.3mm enhanced thermal 16-pin SOP package with additional spacing for high-voltage pins and solderable side-wettable flanks for optical solder joint inspection.

Applications

• High-power automotive DC/DC regulators
• Automotive motor drives
• Hybrid/electric vehicle power supplies

Key features

• Temperature grade 1: ambient temperature range -40°C to +125°C
• Wide input voltage range: 9.5V to 400V
• Adjustable output voltage: 1.25V to 280V
• Voltage mode control with line feedforward
• Three-stage frequency switching
• 60ns minimum on-time for high VIN/VOUT ratio
• 180ns minimum off-time for low dropout
• 1.1V reference voltage with ±1% feedback accuracy
• 8.5V gate driver for standard threshold MOSFETs
• 220ns adaptive dead-time control
• 2A source and 2.5A sink current capability
• Hiccup mode overcurrent protection
• Input UVLO with hysteresis
• VCC and gate driver UVLO protection
• Thermal shutdown with hysteresis
• 16-pin SOP package with wettable flanks