STMicroelectronics LD39150PU-R

Overview

LD39150PU-R from STMicroelectronics is an adjustable ultra-low-dropout linear voltage regulator in DFN6 (3×3 mm) package, delivering up to 1.5 A output current with 200 mV typical dropout at full load and 1 µA max quiescent current in shutdown mode. It operates from 2.5 V to 6 V input, supports ADJ output from 1.22 V to 5.0 V, and features logic-controlled inhibit, internal current/thermal limiting, and ±1.5% output voltage tolerance at 25 °C - optimized for microprocessor core and memory power rails.

For engineers reviewing the LD39150PU-R datasheet, LD39150PU-R pinout, LD39150PU-R application, or LD39150PU-R equivalent, key selection criteria include dropout performance at 1.5 A, stability with ceramic capacitors ≥2.2 µF, thermal resistance (R_thJA = 40 °C/W with PCB ground plane), and precise inhibit threshold (0.3 V low / 2 V high) for low-power system sequencing.

Technical Context

The LD39150PU-R uses a BiCMOS process enabling load-independent quiescent current - maintaining 1 mA typ. at 1.5 A load while dropping to ≤1 µA in shutdown. Its error amplifier senses output via the VSENSE pin (pin 5), allowing precise ADJ configuration using external resistors per VO = 1.22 V × (1 + R1/R2).

Internal protection includes foldback current limiting (3 A short-circuit peak), thermal shutdown at 170 °C with 10 °C hysteresis, and fast transient response due to high-gain control loop - demonstrated by <15 µs turn-on/off delay and stable operation with CO ESR as low as 5 mΩ across –40 to 125 °C.

Key Specifications

Pinout & Package

LD39150PU-R is housed in a thermally enhanced DFN6 (3 × 3 mm) package with exposed thermal pad (TAB) electrically connected to GND. The 6-pin layout supports space-constrained applications requiring high power density and low profile (<1 mm height).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar adjustable LDO regulator applications.

Compared with TSM1117-ADJ and MCP1826T-ADJ/DC, LD39150PU-R delivers 50% lower dropout, 25× lower shutdown current, and 38% better thermal resistance - making it the optimal choice for thermally constrained, high-current, battery-sensitive applications demanding precision regulation.

Availability

LD39150PU-R is available at Aetrix Electronics and suitable for mobile processor core rails, FPGA I/O banks, automotive memory supplies, and industrial real-time controller power domains requiring stable component supply, long-term lifecycle support, and AEC-Q100-aligned reliability.

Supply support for LD39150PU-R 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, designing and manufacturing silicon solutions for automotive, industrial, and consumer markets since 1987.

The LD39150 belongs to ST's ultra-low-dropout linear regulator product line, engineered specifically for high-efficiency, low-noise post-regulation in battery-powered and thermally constrained embedded systems where precision, stability, and minimal quiescent power are critical.

FAQ

What is the minimum output capacitance required for stability with LD39150PU-R?

The LD39150PU-R requires a minimum 2.2 µF ceramic output capacitor with ESR between 5 mΩ and 50 mΩ for guaranteed stability across –40 to 125 °C. Lower ESR values are acceptable if CO is increased per Figure 15/16 in the datasheet; tantalum capacitors may be used but require careful ESR verification.

Can LD39150PU-R be used without connecting the VINH pin?

No - the VINH pin is not internally pulled up or down and must never be left floating. If inhibit functionality is unused, VINH must be tied directly to VI (input voltage) to maintain continuous operation. Leaving it unconnected risks erratic enable/disable behavior and potential damage from undefined logic states.

How does the VSENSE pin function in the LD39150PU-R adjustable configuration?

In LD39150PU-R, pin 5 (VSENSE) serves as the error amplifier's inverting input. It connects to the junction of R1 and R2 in the external feedback divider, enabling VO = 1.22 V × (1 + R1/R2). Unlike fixed-output variants, VSENSE replaces internal resistors - allowing precise, user-defined output voltages from 1.22 V to 5.0 V with ±1.5% tolerance.

What thermal derating applies when operating LD39150PU-R at 1.5 A in still air?

With the DFN6 package mounted on a 4-layer PCB with 1-in² 1-oz copper ground plane, LD39150PU-R sustains 1.5 A continuously up to 85 °C ambient. Above that, output current must be linearly reduced per R_thJA = 40 °C/W: at 100 °C ambient, max safe load drops to ~1.15 A to keep junction temperature ≤125 °C.