STMicroelectronics L6728AHTR

Overview

L6728AHTR from STMicroelectronics is a single-phase synchronous buck PWM controller with integrated high-current gate drivers, 0.8 V internal reference, ±0.8% output voltage accuracy, fixed 600 kHz switching frequency, and sensorless over-current protection via low-side R_DS(on) sensing - designed for CPU/DSP and subsystem power supplies requiring fast transient response and pre-bias start-up capability.

For engineers reviewing the L6728AHTR datasheet, L6728AHTR pinout, L6728AHTR application, or L6728AHTR equivalent, key selection considerations include its VFDFPN10 3×3 mm package, adaptive dead-time control, LS-LESS pre-bias startup, programmable dual-level OCP, and VSEN-based PGOOD monitoring with ±3% window tolerance.

Technical Context

L6728AHTR implements voltage-mode control with a 15 MHz GBWP error amplifier and 8 V/μs slew rate to support high-bandwidth regulation. Its oscillator is fixed at 600 kHz (±10%), enabling predictable EMI filtering and compact magnetics design.

The controller uses PHASE pin sensing for adaptive dead-time control and monitors current through low-side MOSFET R_DS(on) without external sense resistors. It features dual-level OCP (programmable 1st level + 1.5× internal 2nd level), VSEN-based OVP/UVP (0.9–1.1 V / 0.5–0.7 V thresholds), and latched shutdown requiring VCC cycle recovery.

Key Specifications

Pinout & Package

Supplied in VFDFPN10 (also labeled VFQFPN10) 3 mm × 3 mm, 0.5 mm pitch, exposed thermal pad package - optimized for high-power density DC-DC converters with low thermal resistance (R_TH(JA) = 45 °C/W on 2s2p board).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ISL6263CRZ-T and TPS54620RGYR, L6728AHTR offers superior protection integrity via VSEN, safer startup into pre-biased rails, and cost-effective sensorless OCP - making it optimal for high-reliability CPU/memory subsystems where fault coverage and layout simplicity are critical.

Availability

L6728AHTR is available at Aetrix Electronics and suitable for CPU core supplies, memory termination rails, and MCH/IOCH subsystem power requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L6728AHTR 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, delivering automotive, industrial, and power management ICs with emphasis on energy efficiency and system integration.

L6728AHTR belongs to ST's high-frequency DC-DC controller product line, engineered specifically for compact, high-efficiency synchronous buck converters in computing and communications infrastructure where precision regulation and robust protection are mandatory.

FAQ

What is the function of the VSEN pin, and how does it differ from the FB pin?

The VSEN pin provides an independent, dedicated path for output voltage monitoring used exclusively for overvoltage, undervoltage, and PGOOD functions - it is electrically isolated from the feedback loop. Unlike FB, which feeds the error amplifier for regulation, VSEN remains active even if the FB network fails or disconnects, ensuring fail-safe protection integrity. Its 0.68–0.92 V detection window guarantees reliable power-good assertion across temperature and load.

How does LS-LESS startup prevent negative voltage spikes during pre-biased output conditions?

During LS-LESS startup, the low-side MOSFET remains disabled until the high-side begins switching, preventing reverse current flow through the inductor when the output is already charged above the target voltage. If the output remains pre-biased after soft-start completes, the LS driver activates to discharge the rail safely to the regulated value - avoiding dangerous undershoot and protecting downstream logic from negative transients.

Can the L6728AHTR be used with input voltages below 5 V?

No - the VCC supply must be between 5 V and 12 V per absolute maximum ratings and functional specifications. However, the power conversion input (VIN) can be as low as 1.5 V because the controller drives external MOSFETs; the 5–12 V VCC requirement applies only to the IC's internal logic and gate drivers, not the main power path.

What happens when over-current protection triggers, and how is recovery performed?

Upon detection of either four consecutive 1st-level OCP events or one 2nd-level OCP event, L6728AHTR enters latched shutdown: both UGATE and LGATE are forced low and remain inactive. Recovery requires cycling the VCC supply - the device does not auto-restart. This ensures system-level fault containment and prevents repeated stress on MOSFETs or load during persistent overloads or shorts.