STMicroelectronics L6911D

Overview

L6911D from STMicroelectronics is a synchronous buck DC-DC controller IC designed for high-current microprocessor core power supplies. It delivers precise 5-bit VID-programmable output voltage (1.100 V to 1.850 V in 25 mV steps), ±1% output accuracy over line/temperature, and up to 1.3 A gate drive current for N-channel MOSFETs in VRM 9.0-compliant systems.

For engineers reviewing the L6911D datasheet, L6911D pinout, L6911D application, or L6911D equivalent, key selection criteria include its voltage-mode PWM control architecture, 200 kHz–1 MHz adjustable switching frequency, soft-start/inhibit functions, and integrated overvoltage/overcurrent protection using upper MOSFET R_DS(on) sensing.

Technical Context

The L6911D implements voltage-mode PWM control with a 15 MHz gain-bandwidth error amplifier and 10 V/µs slew rate to support fast transient response. Its internal 5-bit DAC sets both output regulation voltage and associated PGOOD/OVP thresholds via TTL-compatible VID0–VID4 inputs.

Protection logic uses adaptive monitoring: overvoltage detection triggers OVP pin high (for external SCR crowbar) and forces LGATE on; overcurrent is sensed across the upper MOSFET's R_DS(on) via OCSET pin, initiating HICCUP-mode recovery. The oscillator frequency is externally programmable via RT pin with ±15% variation over 50 kHz–1 MHz range.

Key Specifications

Pinout & Package

Package: SO-20 (Small Outline, 20-pin, surface-mount).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck controller applications.

Compared with ISL6522CRZ and TPS51116PWR, the L6911D uniquely combines VRM 9.0-compliant 5-bit VID, R_DS(on)-based overcurrent protection, and a dedicated OVP crowbar output - making it optimal for cost-sensitive, high-reliability server/desktop core supplies where component count and fail-safe shutdown are prioritized.

Availability

L6911D is available at Aetrix Electronics and suitable for desktop CPU core power supplies, server VRM modules, and industrial embedded MPU power systems requiring stable component supply and long-lifecycle support.

Supply support for L6911D 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, microcontrollers, and analog ICs for industrial, automotive, and computing markets.

The L6911D belongs to ST's VRM-compliant DC-DC controller product line, engineered specifically for high-current, low-voltage microprocessor core regulation with integrated protection and programmability.

FAQ

What is the minimum recommended output capacitance for L6911D in a 1.2 V/15 A application?

The L6911D requires sufficient output capacitance to limit voltage droop during fast load transients. For a 1.2 V/15 A design with 10 A/µs slew rate, ST recommends ≥1200 µF total ceramic+polymer capacitance with ≤2 mΩ total ESR to hold ∆V_OUT < 50 mV during 0–100% load steps. Layout must minimize ESL with parallel low-inductance capacitors near the CPU.

Can L6911D operate with an input voltage below 5 V?

No. The L6911D requires V_CC between 5 V and 12 V for proper internal biasing and gate driver operation. Input bus voltages below 5 V will not meet the 4.6 V turn-on threshold, preventing startup. For sub-5 V input systems, a dedicated bias supply or auxiliary LDO is required to power V_CC.

How does the L6911D implement overvoltage protection without external components?

The L6911D monitors VSEN against the DAC-set reference and triggers OVP at +17% nominal. It asserts the open-drain OVP pin high to drive an external SCR for input crowbar, while simultaneously turning on LGATE to short the output. This dual-action - active crowbar plus synchronous rectifier clamping - provides hardware-level fail-safe protection without additional comparators or timers.

What is the purpose of the SS/INH pin's dual function?

The SS/INH pin serves two distinct roles: during startup, a 10 µA current charges an external capacitor to generate a controlled voltage ramp for soft-start; during operation, pulling this pin below 0.4 V forces immediate disablement of both UGATE and LGATE, halting switching and placing the device in a safe, low-power inhibit state - useful for system-level power sequencing or thermal shutdown.