STMicroelectronics L6728DTR

Overview

L6728DTR 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 300 kHz switching frequency, and programmable dual-level overcurrent protection via low-side R_DS(on) sensing - used in CPU/DSP core power supplies requiring precise regulation and pre-bias start-up capability.

For engineers reviewing the L6728DTR datasheet, L6728DTR pinout, L6728DTR application, or L6728DTR equivalent, key selection considerations include its DFN10 3×3 mm package, VCC supply range (5–12 V), VIN as low as 1.5 V, sensorless OCP programming via ROCSET resistor, PGOOD monitoring via dedicated VSEN pin, and LSless pre-bias start-up behavior.

Technical Context

L6728DTR implements voltage-mode control with a 15 MHz GBWP error amplifier and 8 V/μs slew rate for fast transient response. Its adaptive dead-time logic monitors PHASE and LGATE to prevent shoot-through while enabling body-diode conduction minimization without external Schottky diodes.

The controller supports sensorless current sensing by comparing PHASE node voltage during low-side conduction against two internally held thresholds - first level set externally via 10 μA IOCSET current into ROCSET (5–55 kΩ), second level fixed at 1.5× first level - triggering latched shutdown on violation.

Key Specifications

Pinout & Package

Supplied in a thermally enhanced DFN10 (3 mm × 3 mm, 0.5 mm pitch) package with exposed thermal pad for efficient heat dissipation in high-current applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ISL6260CRZ and TPS54620RGYR, L6728DTR uniquely combines LSless start-up, VSEN-dedicated monitoring, and sensorless OCP in a DFN10 package - making it optimal for CPU/memory power where pre-bias immunity and protection independence are critical.

Availability

L6728DTR is available at Aetrix Electronics and suitable for CPU core power supplies, memory termination systems, and subsystem power rails requiring stable component supply, long-term lifecycle assurance, and consistent parametric performance across production batches.

Supply support for L6728DTR 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, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

L6728DTR belongs to ST's high-performance power management controller family, engineered specifically for efficient, compact, and robust point-of-load DC-DC conversion in computing and communications infrastructure.

FAQ

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

VSEN provides an independent analog path for output voltage monitoring-used exclusively for PGOOD assertion, overvoltage, and undervoltage protection. Unlike FB, which feeds the error amplifier for regulation, VSEN bypasses the feedback divider, ensuring protection accuracy remains unaffected by resistor tolerance or temperature drift. This separation guarantees reliable system sequencing and fault response even if the FB network is compromised.

How does the LSless start-up feature work, and when is it activated?

LSless disables the low-side gate driver during soft-start until the high-side begins switching. If the output is pre-biased above the target voltage, LS remains off until soft-start completes, then activates to discharge the rail to regulation. This prevents reverse inductor current and dangerous negative voltage spikes at the load-critical for systems powering FPGA or ASICs with charged output capacitors at power-on.

Can L6728DTR operate with input voltages below 5 V, and what are the limitations?

Yes-L6728DTR supports power conversion inputs as low as 1.5 V, but its VCC supply must remain within 5–12 V. The controller derives gate drive from VCC (for LS) and BOOT (for HS), so low VIN operation requires a separate 5–12 V bias rail. Minimum VIN is constrained by maximum duty cycle (80 %), meaning VOUT must be ≤0.8 × VIN to maintain regulation-e.g., 1.5 V input supports up to 1.2 V output.

What happens when overcurrent protection triggers, and how is recovery performed?

Upon OCP trigger-either four consecutive first-level events or one second-level event-the device latches both HS and LS gate outputs OFF and holds them inactive. Recovery requires cycling the VCC supply: removing and reapplying VCC resets internal logic, clears the latch, and restarts soft-start. No external reset pin or command is provided; this ensures fail-safe shutdown until system-level intervention confirms fault clearance.