STMicroelectronics L6911C

Overview

L6911C from STMicroelectronics is a synchronous buck DC-DC controller IC designed for high-current microprocessor core power supplies, featuring 5-bit VID-programmable output (1.30V–3.50V), ±1% output accuracy over line/temperature, 1.3A gate drive capability, voltage-mode PWM control, and integrated overvoltage/overcurrent protection using upper MOSFET R_DS(on) sensing.

For engineers reviewing the L6911C datasheet, L6911C pinout, L6911C application, or L6911C equivalent, this controller supports VRM 8.4-compliant voltage scaling, fast load transient response (0%→100% duty cycle), programmable 50–1000 kHz switching frequency, soft-start/inhibit control, and power-good signaling - critical for advanced CPU power delivery design and validation.

Technical Context

The L6911C implements voltage-mode PWM control with a precision internal 1.235V reference and a 5-bit DAC to generate the V_PROG setpoint, enabling binary-stepped output regulation per VRM 8.4. Its error amplifier delivers 88 dB DC gain, 10 MHz GBWP, and 10 V/µs slew rate to support high-bandwidth loop compensation for fast transient suppression.

Protection logic uses real-time monitoring of VSEN, OCSET (via 200 µA current source), OVP, and PGOOD pins: overvoltage triggers both internal low-side crowbar activation and external SCR gating; overcurrent detection forces HICCUP-mode restart via SS capacitor discharge; soft-start is implemented with 10 µA constant-current ramping of an external capacitor.

Key Specifications

Pinout & Package

Package: SO-20 (Small Outline, 20-pin, surface-mount). Thermal resistance R_{th j-amb} = 110°C/W; max junction temperature = 150°C.

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 L6911C offers unique R_DS(on)-based overcurrent protection, programmable 50–1000 kHz frequency, and dedicated OVP crowbar output - making it optimal for high-reliability, field-serviceable CPU power systems where component count reduction and fail-safe shutdown are prioritized.

Availability

L6911C is available at Aetrix Electronics and suitable for desktop CPU core power supplies, server VRM modules, and industrial embedded MPU supplies requiring stable component supply, long-lifecycle support, and legacy design continuity.

Supply support for L6911C 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, microcontrollers, and analog ICs for industrial, automotive, and computing markets.

The L6911C belongs to ST's high-performance power supply controller product line, engineered specifically for VRM-compliant microprocessor core voltage regulation with emphasis on accuracy, transient response, and integrated protection.

FAQ

What is the minimum recommended output capacitance for L6911C when powering a 60A CPU load?

The minimum output capacitance depends on allowable voltage droop during worst-case load transient (e.g., 0→60A in 1 µs). With typical ESR ≤2 mΩ and ∆I=60A, ∆V_OUT = ∆I × ESR ≈ 120 mV. To limit droop to <50 mV, total C_OUT must be ≥(∆I × L)/(∆V × f_SW) - typically ≥1200 µF ceramic + polymer for 1.5V/60A designs. Layout and ESL minimization are equally critical.

Can L6911C operate with a 3.3V input supply?

No. The L6911C requires VCC between 5V and 12V per absolute maximum ratings and functional specifications. Its gate drivers and internal references are not characterized below 5V. Attempting 3.3V operation will result in undervoltage lockout (UVLO), disabling UGATE/LGATE outputs and preventing regulation.

How does the L6911C implement overvoltage protection without external components?

The L6911C monitors VSEN against a VID-derived threshold (+17% nominal). When exceeded, it drives OVP pin high to trigger an external SCR crowbar and simultaneously turns on LGATE continuously to short the output to PGND - providing dual-path protection. No external comparator or reference is needed for basic OVP function.

Is the L6911C pin-compatible with newer STMicroelectronics controllers like the L6920DB?

No. The L6911C (SO-20) has distinct pin functions, VID encoding, and protection architecture versus the L6920DB (MSOP-10), which integrates MOSFETs and uses different fault-handling logic. Direct replacement requires schematic and layout redesign; migration should follow ST's official upgrade path documentation.