STMicroelectronics L6788A

Overview

L6788A from STMicroelectronics is a 3-phase synchronous buck controller with integrated high-current gate drivers, designed for GPU core voltage regulation. It supports 1/2/3-phase operation, delivers up to 1.350 V output with ±2% accuracy via serial/parallel VID, and features full differential current sensing, remote voltage sensing, and 5 V LDO output. Used in high-current DC-DC converters for discrete and integrated graphics cards.

For engineers reviewing the L6788A datasheet, L6788A pinout, L6788A application, or L6788A equivalent, key selection criteria include phase scalability, thermal management architecture, droop programming via RT/DROOP pin, SMBus programmability for power sequencing, and robust OCP/UVP/OVP protection with latched fault handling.

Technical Context

The L6788A implements adaptive anti-cross-conduction logic per phase, with three independent PWM channels (PWM1–PWM3) driving high-side (UGATE1–3) and low-side (LGATE1–3) MOSFETs. Its oscillator supports 200–800 kHz switching frequency via external RT resistor, and it embeds a 1.240 V internal reference for precise DAC-based voltage setting.

Thermal monitoring uses dual-threshold comparison on TCS pin (1.500 V warning / 2.500 V shutdown), while VR_HOT/EN serves as both enable input and thermal status output. Current sensing employs differential inputs (CS1±–CS3±) across each inductor, with average current sharing correction and total delivered current monitoring via IOUT/OCP.

Key Specifications

Pinout & Package

VPQFN40 package (6 × 6 mm, 0.5 mm pitch) with exposed thermal pad soldered to PGND plane. Pin 41 (PGND) and the exposed pad provide primary thermal path; recommended layout uses 16 vias under pad for optimal junction-to-PCB conduction.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar multi-phase buck controller applications.

Compared with ISL6367IRZ and TPS53679RSLR, the L6788A uniquely combines 3-phase flexibility, embedded 5 V LDO, SMBus telemetry, and dual-threshold thermal monitoring-making it purpose-built for discrete GPU power delivery where space, thermal awareness, and VID agility are critical.

Availability

L6788A is available at Aetrix Electronics and suitable for graphics card GPU supply, high-performance CPU VRM, and AI accelerator board power requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for L6788A 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 automotive, industrial, and computing markets.

The L6788A belongs to ST's VRM/VRD controller product line, engineered specifically for next-generation GPU voltage regulation with emphasis on multi-phase scalability, thermal safety, and digital interface readiness.

FAQ

What is the function of the RT/DROOP pin beyond frequency setting?

The RT/DROOP pin serves dual roles: its resistor value sets switching frequency (200–800 kHz), and its voltage level enables or disables droop compensation. When pulled to AGND, droop is active-introducing controlled output voltage reduction under load to improve current sharing. Floating disables droop, enabling fixed-voltage regulation.

How does the L6788A handle startup into a pre-biased output?

The L6788A implements LSLess (Lossless Soft-Start) startup, which detects pre-bias on VOUT via VSEN and suppresses high-side gate drive until output voltage rises above the target. This prevents reverse current flow through low-side FETs and avoids damaging inductor saturation or output capacitor stress during hot-insertion scenarios.

Can the 5VCC output power external components like SMBus transceivers?

Yes-the 5VCC pin delivers up to 25 mA at ±2.5% accuracy when VCC1_IC ≥ 8 V. It is explicitly intended to power SMBus pull-up resistors, level shifters, or small logic devices. A 470 nF–2.2 µF ceramic capacitor to PGND is mandatory for stability, and loading beyond 25 mA risks dropout or regulation loss.

What is the significance of the dual thresholds on the TCS pin?

The TCS pin compares against two internal thresholds: 1.500 V triggers VR_HOT/EN to float (thermal warning), allowing system firmware to throttle clocks; 2.500 V triggers immediate thermal shutdown. This staged response enables graceful degradation before catastrophic failure-critical for GPU thermal management where sustained 90+ °C operation is common but must be monitored proactively.