STMicroelectronics L6743

Overview

L6743 from STMicroelectronics is a dual high-current N-channel MOSFET driver for synchronous buck converters, featuring integrated bootstrap diode, adaptive dead-time control, 5–12 V flexible gate-drive supply, preliminary overvoltage (OV) protection, and HiZ shutdown mode. It drives high-side and low-side MOSFETs in CPU VRM/VRD and high-efficiency DC/DC applications up to several MHz switching frequency.

For engineers reviewing the L6743 datasheet, L6743 pinout, L6743 application, or L6743 equivalent, key selection criteria include bootstrap diode integration, adaptive dead-time management, ±1.8 V PHASE-sensed OV threshold, 2 A UGATE source current, and SO-8/DFN10 package thermal performance (R_thJA = 85 °C/W and 45 °C/W respectively).

Technical Context

The L6743 implements independent high-side and low-side gate drivers with dedicated BOOT–PHASE floating supply path and VCC–GND referenced low-side supply. Its adaptive dead-time logic monitors PHASE voltage transitions to dynamically adjust turn-on timing-activating LS when PHASE falls below ~1.8 V and HS when LGATE drops below ~1 V-to minimize body diode conduction.

Preliminary OV protection operates only during HiZ state (post-UVLO, pre-PWM activation), latching LS ON if PHASE exceeds 1.8 V to safeguard loads from HS failure-induced overvoltage. The embedded bootstrap diode eliminates external diode requirement, while internal 15 kΩ EN pull-down enables robust enable/disable control without external biasing.

Key Specifications

Pinout & Package

Available in SO-8 (standard plastic small-outline) and DFN10 3×3 mm (exposed thermal pad) packages. SO-8 supports through-hole and surface-mount assembly; DFN10 offers superior thermal performance (R_thJA = 45 °C/W) and compact footprint for space-constrained VRM modules.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual high-side/low-side MOSFET driver applications.

Compared with IR2110S and LM5113, L6743 uniquely integrates bootstrap diode, adaptive dead-time, and preliminary OV protection - making it the only option among the three qualified for high-reliability, high-transient CPU VRM designs requiring autonomous startup safety and sub-200 ns timing control.

Availability

L6743 is available at Aetrix Electronics and suitable for desktop CPU VRM, server VRD power stages, and industrial high-efficiency DC/DC converters requiring stable component supply, long-term lifecycle support, and consistent thermal performance across SO-8 and DFN10 variants.

Supply support for L6743 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, specializing in power management, analog, microcontrollers, and automotive ICs with broad manufacturing scale and AEC-Q100 qualification capabilities.

L6743 belongs to ST's VRM/VRD driver product line, engineered specifically for high-current, high-efficiency synchronous buck converters in computing and data center power delivery systems.

FAQ

What is the function of the PHASE pin beyond being the high-side return path?

The PHASE pin serves three critical roles: (1) return path for the high-side driver, (2) sensing node for adaptive dead-time control (triggering LS turn-on when voltage falls below ~1.8 V), and (3) input for preliminary OV protection (latching LS ON if voltage rises above ~1.8 V during HiZ). It must be routed with low inductance and minimal capacitance to preserve timing accuracy and protection responsiveness.

Can L6743 operate with VCC = 5 V while driving 12 V gate signals?

No - L6743 does not generate boosted gate voltages. Its UGATE output swing is limited to V_BOOT – V_PHASE, and LGATE swing is limited to V_VCC – GND. To achieve 12 V gate drive on either side, the corresponding supply (VCC for LS, BOOT for HS) must be set to ≥12 V. At VCC = 5 V, LGATE max output is 5 V; UGATE requires BOOT ≥12 V + V_PHASE swing.

How does the integrated bootstrap diode affect PCB layout versus discrete solutions?

The integrated bootstrap diode removes one SMT component and its associated trace, reducing parasitic inductance and layout area. However, an external R_BOOT (few ohms) is still recommended between BOOT and C_BOOT to limit inrush current and prevent overcharging during negative PHASE spikes - especially in systems omitting Schottky catch diodes.

Is the preliminary OV protection active during normal PWM operation?

No - preliminary OV protection is strictly disabled after the first valid PWM transition following UVLO exit. It operates exclusively during the HiZ window *before* PWM control begins, serving only as a startup safeguard against HS MOSFET shorts. Once PWM is active, overvoltage protection relies entirely on the external PWM controller's feedback loop and fault handling.