STMicroelectronics L6728TR

Overview

L6728TR from STMicroelectronics is a single-phase synchronous buck PWM controller with integrated high-current gate drivers, designed for DC-DC step-down conversion in CPU/DSP and subsystem power supplies. It features a 0.8 V internal reference (±0.8 % accuracy), fixed 300 kHz switching frequency, sensorless overcurrent protection via low-side R_DS(on) sensing, Power Good output, and DFN10 3×3 mm package.

For engineers reviewing the L6728TR datasheet, L6728TR pinout, L6728TR application, or L6728TR equivalent, key selection considerations include its voltage-mode control loop, programmable dual-level OCP, LS-less pre-bias startup capability, VSEN-based OV/UV protection, and compatibility with 5–12 V V_CC and ≥1.5 V input rails.

Technical Context

L6728TR implements a voltage-mode error amplifier with 15 MHz GBWP and 8 V/μs slew rate to support fast transient response in tightly regulated point-of-load applications. Its adaptive anti-cross-conduction logic monitors PHASE and LGATE to dynamically adjust dead time, minimizing body-diode conduction without external Schottky diodes.

The controller supports sensorless current sensing by measuring voltage drop across the low-side MOSFET's R_DS(on) at the PHASE pin, enabling dual-level OCP (programmable 1st level + fixed 1.5× 2nd level). The PGOOD output asserts only after soft-start completion and within ±11 % V_SEN window (0.68–0.92 V), tied directly to output or resistor divider.

Key Specifications

Pinout & Package

Package: DFN10 (3 mm × 3 mm, 0.5 mm pitch, exposed thermal pad).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ISL6269CRZ-T and TPS54620RGYR, L6728TR offers unique VSEN-based independent protection, LS-less startup for pre-biased loads, and true controller-level flexibility with external MOSFET selection-critical for high-reliability industrial and computing power designs.

Availability

L6728TR is available at Aetrix Electronics and suitable for CPU core supplies, memory termination rails, MCH/IOCH subsystem power, and PCIe distributed power applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for L6728TR 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.

L6728TR belongs to ST's high-performance DC-DC controller product line, engineered specifically for efficient, compact, and robust point-of-load regulation in demanding computing and communications infrastructure.

FAQ

What is the function of the VSEN pin on L6728TR?

The VSEN pin provides dedicated monitoring of the regulated output voltage for overvoltage (OVP), undervoltage (UVP), and Power Good (PGOOD) functions. It operates independently from the FB pin, allowing accurate protection thresholds (e.g., OVP = 0.97–1.03 V) without being affected by FB resistor divider tolerance or noise-critical for system-level reliability.

How does the LS-less startup feature work, and why is it important?

LS-less startup delays activation of the low-side MOSFET until the high-side begins switching, preventing reverse current flow into a pre-biased output. This avoids dangerous negative voltage spikes and inductor current reversal during cold start-essential for systems with hot-swappable modules or shared power rails where output capacitance may retain charge.

Can L6728TR regulate output voltages below 0.8 V?

No-L6728TR has a fixed 0.8 V internal reference and is not designed to regulate below that threshold. Its minimum output is 0.8 V, achieved by connecting FB directly to the output. Higher voltages are set using an external resistor divider from output to FB and from FB to GND, scaling the feedback accordingly.

What happens when overcurrent protection triggers on L6728TR?

Upon 2nd-level OCP detection-or four consecutive 1st-level events-the device latches both UGATE and LGATE low and halts switching. Recovery requires cycling the VCC supply to reset the protection state. This hard latch prevents repeated fault attempts and protects downstream MOSFETs and load circuitry from sustained overcurrent stress.