STMicroelectronics L6731DTR

Overview

L6731DTR from STMicroelectronics is an adjustable synchronous step-down controller designed for DDR memory supply, DDR termination supply, low-voltage distributed DC/DC conversion, and high-current point-of-load power rails. The device drives external N-channel MOSFETs, supports a 1.8 V to 14 V converter input range, operates from a 4.5 V to 14 V controller supply, and regulates output voltage down to 0.6 V.

For engineers reviewing the L6731DTR datasheet, L6731DTR pinout, L6731DTR application, or L6731DTR equivalent, this controller is most relevant for DDR VDDQ / VTT power stages, graphics-card rails, niPoL converters, compact DC/DC modules, and synchronous buck layouts requiring source / sink capability, selectable 250 kHz / 500 kHz operation, programmable MOSFET RDS(on) current sensing, and HTSSOP16 exposed-pad tape-and-reel assembly.

Technical Context

L6731DTR uses fixed-frequency voltage-mode PWM control and drives an external high-side and low-side MOSFET pair through HGATE and LGATE. Its 0% to 100% duty-cycle capability and below-100 ns minimum on-time support low-output-voltage buck conversion from intermediate buses, while the ±0.8% reference accuracy over line voltage and temperature supports tight DDR and low-voltage rail regulation.

For DDR power designs, the DDR-IN pin controls internal or external reference operation and selects the switching frequency. The internal divider and buffer generate VTTREF at one-half of DDR-IN, allowing VTT and VTTREF regulation within 1% of VDDQ. Protection functions include power good, high-side peak current limit, low-side valley current limit, overvoltage protection, feedback disconnection detection, hiccup overcurrent response, and thermal shutdown.

Key Specifications

Pinout & Package

L6731DTR is supplied in an HTSSOP16 exposed-pad package with 0.65 mm lead pitch and tape-and-reel production packaging. The exposed-pad TSSOP format supports compact synchronous buck controller placement, improved PCB grounding, and better thermal transfer while keeping the gate-drive, phase-node, compensation, DDR reference, and current-limit pins accessible for dense power-stage routing.

Key Features

• Adjustable synchronous buck controller for DDR memory supply and termination rails.
• 1.8 V to 14 V converter input range and 4.5 V to 14 V controller supply range.
• Output voltage adjustable down to 0.6 V with ±0.8% reference accuracy.
• VTT and VTTREF regulation within 1% of VDDQ for DDR memory power requirements.
• Selectable 250 kHz / 500 kHz fixed-frequency voltage-mode PWM operation.
• Source / sink capability for DDR termination supply behavior.
• Programmable high-side and low-side MOSFET RDS(on) overcurrent sensing.
• Power-good output, soft-start / inhibit, overvoltage protection, hiccup-mode OCP, and thermal shutdown.

Applications

Equivalent & Alternatives

When evaluating L6731DTR equivalent devices, engineers should compare DDR reference behavior, source / sink capability, converter input range, output accuracy, switching frequency selection, MOSFET driver strength, RDS(on) current-limit method, HTSSOP16 footprint, and tape-and-reel assembly requirements.

Compared with L6731D, L6731DTR keeps the same DDR memory supply controller function, pinout, HTSSOP16 package, MOSFET driver structure, and protection behavior. L6731DTR vs L6731D selection depends mainly on tape-and-reel versus tube packaging logistics, rather than a change in the electrical power-stage design.

Quality

L6731DTR should be sourced as original STMicroelectronics components through traceable and controlled supply channels. Quality verification procedures may include HTSSOP16 exposed-pad package inspection, top-mark validation, tape-and-reel label review, solderability testing, VCCDR regulator output verification, DDR-IN reference behavior checks, HGATE / LGATE driver function testing, PGOOD threshold verification, current-limit setting review, and incoming inspection according to DDR memory power-supply production requirements.

Availability

L6731DTR is available at Aetrix Electronics and suitable for DDR memory supplies, DDR termination rails, low-voltage distributed DC/DC modules, graphic-card power rails, and compact synchronous buck converter designs requiring stable component supply and repeatable production support.

Supply support may include scheduled delivery planning, volume procurement support, BOM continuity assistance, traceable sourcing management, and long-term availability support for OEM manufacturers, memory-module power designers, graphic-card hardware developers, industrial computing builders, and electronics production programs.

For production deployment, confirming the HTSSOP16 exposed-pad package, tape-and-reel format, DDR-IN reference mode, switching-frequency setting, MOSFET driver requirements, current-limit design, thermal requirements, environmental specifications, and sourcing continuity helps reduce procurement risk and improve manufacturing stability.

Manufacturer

STMicroelectronics supplies power-management ICs, controllers, converters, RF devices, discrete semiconductors, sensors, and embedded semiconductor products for computing, industrial, automotive, communication, and consumer systems. L6731DTR belongs to ST's synchronous step-down controller portfolio for DDR memory and low-voltage point-of-load power conversion.

FAQ

What is L6731DTR used for?

L6731DTR is used to control synchronous buck converters for DDR memory supply, DDR termination supply, low-voltage distributed DC/DC rails, niPoL converters, compact DC/DC modules, and graphics-card power rails. It drives external N-channel MOSFETs and supports source / sink behavior needed by DDR termination supplies.

How does L6731DTR support DDR memory power requirements?

L6731DTR includes a DDR-IN input, internal divider, and VTTREF buffer. It can regulate VTT and VTTREF within 1% of VDDQ, and it supports an external reference mode for DDR-related tracking rails. This makes it suitable for memory systems where the termination and reference rails must follow the memory supply relationship.

What switching frequencies can L6731DTR use?

L6731DTR supports two fixed switching-frequency options: 250 kHz and 500 kHz. Engineers select the frequency based on inductor size, MOSFET switching loss, transient response, output ripple, thermal behavior, and EMI constraints in the final buck converter layout.

How does L6731DTR implement overcurrent protection?

L6731DTR uses MOSFET RDS(on) sensing rather than a dedicated current-sense resistor. The OCH pin sets high-side peak current limit, while the OCL pin sets low-side valley current limit. This approach saves board space and power loss, but the engineer must account for MOSFET RDS(on) tolerance, temperature rise, layout parasitics, and required load-current margin.

What should be considered in L6731DTR PCB layout?

L6731DTR layout should keep PGND close to the low-side MOSFET source, route PHASE carefully because it is both a switching node and current-sense reference, place the BOOT-to-PHASE capacitor close to the IC, bypass VCCDR with local ceramic capacitance, and keep FB / COMP compensation traces away from noisy gate-drive and switch-node paths.

What package is used by L6731DTR?

L6731DTR uses an HTSSOP16 exposed-pad package supplied in tape-and-reel format. The exposed pad improves grounding, thermal transfer, and mechanical stability, while the 16-pin layout keeps the DDR reference, feedback, gate-drive, bootstrap, phase, and current-limit pins accessible for compact power-stage design.

What is the difference between L6731DTR and L6731D?

L6731DTR and L6731D use the same controller architecture, pinout, package style, and electrical function. The main difference is packaging logistics: L6731DTR is supplied in tape-and-reel format for automated SMT production, while L6731D is supplied in tube packaging.