Rethinking Gate Drivers: Why Integrated Bootstrap Wins

Read Below:

• Modern power electronics demand precise high- and low-side gate driving to switch MOSFETs and IGBTs efficiently, minimizing losses under fast rise/fall times.

• Bootstrap topologies simplify high-side drive by eliminating isolated supplies, reducing Bill-of-material (BOM) cost and PCB complexity.

Launched in May 2025, Littelfuse’s new IXD0579M is a new robust driver IC with an integrated bootstrap diode, available through McKinsey Electronics to speed up buck, boost and half-bridge designs

Whether it's a three-phase inverter for EV traction, a high-fre.quency synchronous buck powering an FPGA or an LLC resonant converter inside a server PSU, modern power systems live and die by their gate drivers. These small but crucial ICs dictate how quickly power transistors turn on or off, directly impacting switching losses, EMI and overall system efficiency.

The problem: driving the high-side MOSFET

In most topologies, the low-side FET is straightforward: its source is tied to ground, so driving the gate just means pulling it above ground.

But for the high-side FET, the source moves up and down, floating relative to ground. If you're switching 48 V or 400 V, you still need to apply 10–15 V above the source pin to fully enhance the device. That means generating a gate voltage that might be 415 V relative to system ground.

How bootstrap gate drive solves it

The most elegant answer is the bootstrap circuit: a small diode plus capacitor network that charges during low-side conduction, storing energy at V_CC - V_F (minus diode drop). When the low-side turns off, this cap serves as a floating supply to drive the high-side gate.

It’s a staple in:

• Half-bridge drivers for motor inverters

• Synchronous buck regulators

• Boost converters

This eliminates the need for isolated gate supplies or expensive transformer-coupled drivers, greatly simplifying the BOM.

The new challenge: high-speed transitions, parasitics & reliability

Modern designs often push >200 kHz switching, with di/dt in the hundreds of A/μs. That stresses traditional bootstrap circuits:

• Recovery time & Q_rr in diodes affect recharge.

• PCB stray inductance can cause false triggering or desaturation.

• Internal level shifters in driver ICs must be robust to fast transients.

The 2025 answer: LittleFuse’s IXD0579M

On May 20, 2025, Littelfuse introduced the IXD0579M, an integrated high-/low-side gate driver with an internal bootstrap diode. This IC streamlines designs by:

• Eliminating external bootstrap diodes, improving reliability and cutting PCB parasitics

• Handling peak gate drive currents of 2 A, with fast rise/fall to minimize MOSFET transition losses

• Supporting direct 4.5–20 V inputs, suitable for both standard trench MOSFETs and newer SiC FETs with lower gate voltage specs.

Why it matters:

Internal bootstrap saves PCB area, reduces ringing and overshoot, and cuts total component count. It’s especially important in automotive or high-rel converters where vibration or thermal cycling can fatigue discrete diode solder joints.

PCB layout tips with high-side drivers

• Minimize loop area for gate charge paths. Place driver close to the MOSFETs, keeping gate traces short and wide.

• Use a solid ground plane for return currents. Remember, the bootstrap capacitor’s ground is not system ground but the switching node.

• Add a small gate resistor (2–5 Ω) to control di/dt and dampen ringing, without compromising speed too much.

Applications: beyond just DC-DC

The IXD0579M is well suited for:

• 48 V half-bridges in mild hybrid automotive systems

• 400 V SiC-based motor drives (when paired with appropriate gate voltage clamps)

• Synchronous boost or buck regulators for telecom and datacenter rails

• Even isolated flyback primary FETs, using the bootstrap for primary clamp FET drive. This may require careful capacitor sizing and startup consideration in isolated topologies.

How McKinsey Electronics supports your designs

McKinsey Electronics provides local on-ground engineering support and direct sourcing for Littelfuse’s latest power semiconductors and drivers. With offices across the Middle East, Türkiye and Africa, we help OEMs integrate solutions like the IXD0579M quickly, with expertise in PCB power integrity, EMC strategies and long-term component availability.

Contact us today.