Texas Instruments LMR36015SFBRNXR

Overview

LMR36015SFBRNXR from Texas Instruments is a synchronous buck DC/DC converter delivering 1.5 A output current across 4.2 V to 60 V input, featuring 1-MHz fixed-frequency operation, FPWM mode for consistent switching under light loads, and –55°C to +150°C junction temperature rating. It integrates high- and low-side MOSFETs and targets rugged industrial power rails in field transmitters, PLC modules, and HVAC systems.

For engineers reviewing the LMR36015SFBRNXR datasheet, LMR36015SFBRNXR pinout, LMR36015SFBRNXR application, or LMR36015SFBRNXR equivalent, key selection criteria include its FPWM capability, 1-MHz switching frequency, HotRod™ VQFN-HR package, CISPR25 Class 5 EMI compliance, and precision enable/power-good functions for system-level monitoring and sequencing.

Technical Context

The LMR36015SFBRNXR uses peak-current-mode control with internal loop compensation and operates exclusively in forced PWM (FPWM) mode-disabling diode emulation to maintain constant 1-MHz switching regardless of load. Its integrated 225-mΩ high-side and 150-mΩ low-side MOSFETs support efficient regulation down to 0.4-V dropout at 1.5-A load.

It features a precision enable input with hysteresis (1.157–1.231 V turn-on, 110-mV hysteresis), a filtered open-drain power-good flag (90–95% lower threshold, 105–110% upper threshold of FB voltage), and thermal shutdown at 170°C with 12°C hysteresis-enabling robust operation in aerospace, defense, and industrial transport environments.

Key Specifications

Pinout & Package

LMR36015SFBRNXR is housed in a 12-pin VQFN-HR (RNX) package measuring 2.00 mm × 3.00 mm with exposed thermal pad, optimized for low parasitic inductance and high thermal performance (R_θJA = 72.5°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMR36015SFBRNXR, the SARNXR variant trades FPWM for superior light-load efficiency at 400 kHz, while the SBRNXR offers 1-MHz auto-mode operation-neither delivers the guaranteed fixed-frequency behavior essential for EMI-critical or timing-sensitive industrial subsystems.

Availability

LMR36015SFBRNXR is available at Aetrix Electronics and suitable for field transmitters, PLC modules, and HVAC systems requiring stable component supply, long-term industrial lifecycle support, and guaranteed 1-MHz FPWM operation.

Supply support for LMR36015SFBRNXR 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies with decades of industrial-grade DC/DC converter expertise.

The LMR36015S family was designed specifically for scalable, rugged industrial power supplies-emphasizing wide input range, extreme temperature resilience, and EMI robustness in space-constrained applications.

FAQ

What distinguishes LMR36015SFBRNXR from other variants in the LMR36015S family?

The LMR36015SFBRNXR is uniquely configured for forced PWM (FPWM) operation at 1 MHz, ensuring constant switching frequency across all load conditions-including light loads-unlike the SARNXR (400 kHz, auto-mode) or SBRNXR (1 MHz, auto-mode) variants. This makes LMR36015SFBRNXR ideal for EMI-sensitive and timing-deterministic applications where frequency variation must be eliminated. Its FPWM feature is factory-set and cannot be disabled.

Does LMR36015SFBRNXR support adjustable output voltage, and what is the minimum achievable V_OUT?

Yes, LMR36015SFBRNXR supports fully adjustable output voltage using an external resistor divider on the FB pin. With its 1.0-V internal reference voltage and precision feedback accuracy (±15 mV), it can regulate outputs as low as 1.0 V (limited by reference tolerance and divider ratio). The device maintains regulation down to 0.4-V dropout at 1.5-A load, enabling stable low-V_OUT operation even near input voltage limits.

How does the power-good (PG) function of LMR36015SFBRNXR behave during startup and fault conditions?

The LMR36015SFBRNXR's PG pin is an open-drain output with built-in glitch filtering (80–200 µs delay) and dual thresholds: it asserts high when V_OUT reaches 105–110% of the FB reference and deasserts low when V_OUT falls to 90–95%. During startup, PG remains low for ~4 ms after EN assertion before going high-providing a clean system reset signal. It also pulls low during thermal shutdown, current limit hiccup, or EN deactivation, ensuring reliable system supervision.

Can LMR36015SFBRNXR operate reliably at –55°C, and what design considerations apply?

Yes, LMR36015SFBRNXR is fully specified and tested for operation from –55°C to +150°C junction temperature. To ensure reliability at –55°C, use X7R or C0G ceramic capacitors for C_IN, C_OUT, and C_BOOT; verify inductor saturation current derating at low temperature; and ensure PCB layout minimizes thermal gradients. The device's internal VCC LDO (4.75–5.25 V) and FB reference (0.985–1.015 V) remain stable across this full range.

What thermal performance can be expected from LMR36015SFBRNXR in a standard 2-layer PCB layout?

In a standard 2-layer PCB with 1-in² 2-oz copper thermal pad connected to PGND, LMR36015SFBRNXR achieves a junction-to-board thermal resistance (R_θJB) of 23.3°C/W. At 1.5-A load and 24-V input, typical power dissipation is ~0.45 W, resulting in ~10.5°C rise above board temperature. For continuous 1.5-A operation at +85°C ambient, board temperature should be kept ≤ +75°C-achievable with modest copper area and airflow.