STMicroelectronics L6741

Overview

L6741 from STMicroelectronics is a dual high-current N-channel MOSFET driver for synchronous-rectified buck converters, featuring integrated bootstrap diode, adaptive dead-time control, 5–12 V gate-drive flexibility, preliminary OV protection, and SO-8 package. It drives both high-side and low-side MOSFETs in high-current VRM/VRD applications for desktop/server CPUs.

For engineers reviewing the L6741 datasheet, L6741 pinout, L6741 application, or L6741 equivalent, key selection considerations include bootstrap diode integration, HiZ shutdown behavior, adaptive anti-shoot-through timing, PVCC/VCC voltage decoupling flexibility, and PHASE-pin-based OV threshold triggering during HiZ state.

Technical Context

The L6741 implements independent high-side (UGATE/BOOT/PHASE) and low-side (LGATE/VCC/GND) drive paths with separate supply rails (PVCC for HS, VCC for LS), enabling optimized gate voltage selection per FET. Its adaptive dead-time logic monitors PHASE and LGATE voltages to dynamically sequence turn-on and prevent shoot-through.

Preliminary OV protection activates only after UVLO exit and during PWM HiZ state, latching LGATE ON when PHASE exceeds 1.8 V - a hardware-level safeguard independent of external controller response time. The embedded bootstrap diode (anode at PVCC, cathode internally tied to BOOT) eliminates external diode requirement while requiring careful CBOOT sizing per Qg and switching frequency.

Key Specifications

Pinout & Package

Package: SO-8 (ECOPACK®, lead-free, 1.27 mm pitch). Thermal resistance RthJA = 85 °C/W on 2s2p PCB (67 mm × 67 mm).

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 IR2110 and LM5113, L6741 uniquely integrates bootstrap diode, adaptive dead-time, HiZ management, and hardware OV latch - making it purpose-built for high-reliability, high-current synchronous buck VRMs where protection timing and layout simplicity are critical.

Availability

L6741 is available at Aetrix Electronics and suitable for desktop CPU VRMs, server VRDs, and high-density DC/DC converters requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for L6741 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, Switzerland, specializing in power management, analog, microcontrollers, and automotive ICs with vertical manufacturing and broad distribution.

L6741 belongs to ST's VRM/VRD driver product line, engineered specifically for high-current, high-efficiency synchronous buck converters powering modern CPUs - emphasizing protection integrity, thermal robustness, and layout simplicity in space-constrained server/desktop platforms.

FAQ

What is the function of the PHASE pin beyond being the HS return path?

The PHASE pin serves three critical functions: (1) return path for the high-side driver, (2) input for adaptive dead-time control (monitored for falling edge ~2 V to trigger LS turn-on), and (3) sensing node for preliminary OV protection (rising edge >1.8 V during HiZ triggers LS latch-on). It must be routed with low inductance and minimal capacitance to ensure accurate timing and protection response.

Can L6741 operate with VCC and PVCC supplied from the same rail?

Yes - L6741 supports single-supply operation where VCC = PVCC (e.g., both tied to 12 V), as confirmed in Figure 8 of the datasheet. This configuration simplifies power delivery but reduces independent optimization of HS/LS gate drive voltage; dual-rail operation (e.g., VCC = 5 V, PVCC = 12 V) is preferred for maximum efficiency in high-current VRMs.

How does the preliminary OV protection interact with the external PWM controller?

Preliminary OV protection is fully autonomous: it activates only after VCC exits UVLO and while PWM is in HiZ (floating or within 1–2.3 V window), latching LGATE ON if PHASE exceeds 1.8 V. It deactivates automatically upon first valid PWM transition, handing control back to the external controller - providing fail-safe coverage during boot before the controller is fully operational.

Is an external bootstrap diode required when using L6741?

No - L6741 integrates a bootstrap diode with anode connected to PVCC and cathode internally tied to BOOT. However, an external series resistor (RBOOT, typically 1–5 Ω) is recommended between BOOT and CBOOT to limit inrush current and prevent overcharging during large negative PHASE spikes, especially in systems without Schottky catch diodes.