STMicroelectronics L6739TR

Overview

L6739TR 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 memory subsystem supplies. It supports input as low as 1.5 V, features 0.8 V internal reference with ±0.5% output voltage accuracy, programmable oscillator up to 600 kHz, and light-load efficiency optimization via proprietary algorithm.

For engineers reviewing the L6739TR datasheet, L6739TR pinout, L6739TR application, or L6739TR equivalent, key selection considerations include DCR-based sensorless overcurrent protection, remote sensing capability (VSEN/FBG), LS-less pre-bias startup sequence, VFQFPN16 package thermal performance, and 0.5% voltage regulation tolerance across line/temperature.

Technical Context

The L6739TR implements voltage-mode control with a 15 MHz gain-bandwidth error amplifier and 8 V/µs slew rate for fast transient response. Its adaptive deadtime management uses PHASE pin monitoring, while embedded bootstrap switch (R_BOOT = 11 Ω) and high-current drivers (I_UGATE = 2 A source, I_LGATE = 2 A source) enable direct N-MOSFET drive without external drivers.

Protection architecture includes programmable overvoltage (0.89–0.95 V trip), undervoltage (0.57–0.63 V), overtemperature (140 °C shutdown, 40 °C hysteresis), and DCR-based current sensing with 20 mV typical OC threshold and 7-cycle latching. The LS-less startup sequence prevents negative output spikes during pre-biased conditions.

Key Specifications

Pinout & Package

The L6739TR is housed in a VFQFPN16 package (3 mm × 3 mm, 0.5 mm pitch) with an exposed thermal pad for enhanced PCB heat dissipation. Thermal resistance junction-to-case is 1 °C/W; junction-to-ambient is 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 ISL6322IRZ and TPS54620RGYR, the L6739TR uniquely combines integrated drivers, DCR-based current sensing, remote sensing (VSEN/FBG), and LS-less startup in a compact VFQFPN16 - making it optimal for space-constrained, high-accuracy single-phase applications requiring pre-bias robustness and thermal efficiency.

Availability

L6739TR is available at Aetrix Electronics and suitable for CPU core power supply, memory termination supply, and distributed DC-DC converter applications requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for L6739TR 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 with strong automotive and industrial focus.

The L6739TR belongs to ST's high-efficiency DC-DC controller product line, engineered specifically for single-phase synchronous buck converters in computing and communications infrastructure where precision regulation, thermal efficiency, and startup reliability are critical.

FAQ

What is the minimum input voltage supported by the L6739TR for power conversion?

The L6739TR supports power conversion input as low as 1.5 V, enabled by its flexible architecture that decouples the controller's VCC supply (4.75–13.2 V bus) from the power path. This allows operation with very low VIN rails while maintaining full functionality including DCR sensing, PGOOD, and protections - ideal for intermediate bus architectures feeding downstream POL stages.

How does the LS-less startup feature prevent output voltage undershoot?

The LS-less startup delays activation of the low-side MOSFET until the first PWM pulse occurs during soft-start. This avoids reverse current flow through the inductor when the output is pre-biased, eliminating dangerous negative voltage spikes at the load. Protections remain active - OV can still force LS turn-on if needed - but normal startup proceeds without disruptive undershoot.

Can the L6739TR regulate output voltages below 0.8 V?

No - the L6739TR has a fixed 0.8 V internal reference and is not designed for sub-0.8 V regulation. Output voltages equal to or above 0.8 V are set using an external resistor divider from VOUT to FB and FB to FBG (for remote sensing). Attempting lower outputs would violate the internal reference architecture and compromise accuracy and protection thresholds.

What thermal design guidance applies to the VFQFPN16 package?

The VFQFPN16 package requires connection of the exposed thermal pad to the PCB's PGND plane using ≥4 thermal vias (0.3 mm diameter, filled or capped). ST specifies R_THJC = 1 °C/W and R_THJA = 45 °C/W on a 2s2p board - achieving this requires copper area ≥100 mm² under the pad and proper layer stacking. Avoid solder mask over the pad to maximize thermal transfer.