STMicroelectronics LD39115J28R

Overview

LD39115J28R from STMicroelectronics is a 150 mA ultra-low-noise, low-quiescent-current LDO voltage regulator delivering a fixed 2.8 V output with ±2.0 % tolerance at 25 °C. It operates from 1.5 V to 5.5 V input, features 80 mV typical dropout at 100 mA, 33 µV_RMS noise (1–100 kHz), and logic-controlled shutdown (<1 µA off-mode current). It powers core rails in space-constrained, battery-operated portable electronics requiring stable low-noise bias.

For engineers reviewing the LD39115J28R datasheet, LD39115J28R pinout, LD39115J28R application, or LD39115J28R equivalent, key selection criteria include dropout voltage under load, quiescent current across temperature, output noise spectral density, enable threshold stability, and ceramic capacitor compatibility (1 µF C_OUT).

Technical Context

The LD39115J28R uses a bandgap-referenced feedback loop with internal trimming for precise 2.8 V regulation. Its flip-chip 4-bump construction enables compact thermal management and low parasitic inductance. The enable input (EN) controls NMOS pass transistor gate drive, allowing fast turn-on (30 µs) and sub-µA shutdown.

It integrates thermal shutdown (160 °C trip, 20 °C hysteresis) and short-circuit current limiting (~200 mA). Power supply rejection is 74 dB at 1 kHz and 67 dB at 10 kHz, rolling off above 10 kHz-critical for RF-sensitive analog subsystems powered from noisy switched supplies.

Key Specifications

Pinout & Package

LD39115J28R uses a flip-chip 4-bump package (0.8 × 0.8 mm, 0.4 mm pitch) with exposed die pad for thermal conduction. No external heatsink required in typical PCB layouts with 2 oz copper and thermal vias.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6210B282MR-G and RT9013-28GB, LD39115J28R delivers superior noise performance (33 µV_RMS vs. ≥45 µV_RMS) and smallest form factor-critical for ultra-thin mobile and wearable designs where PCB area and EMI sensitivity constrain alternatives.

Availability

LD39115J28R is available at Aetrix Electronics and suitable for mobile handset power rails, wearable sensor node core supply, industrial IoT edge controllers, and automotive infotainment display backlight bias requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LD39115J28R 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 microcontrollers, power management ICs, sensors, and analog devices for industrial, automotive, and consumer markets.

The LD39115J series belongs to ST's ultra-low-noise LDO portfolio, engineered specifically for battery-powered portable electronics demanding minimal IQ, sub-100 mV dropout, and µV-level noise in sub-1 mm² packages.

FAQ

What is the minimum input voltage required for LD39115J28R to maintain regulation at full 150 mA load?

The LD39115J28R requires VIN ≥ VOUT + VDROP to sustain regulation. With 2.8 V output and 110 mV max dropout (over temperature), minimum VIN is 2.91 V at 150 mA. At room temperature, 80 mV typical dropout allows regulation down to 2.88 V input. Below this, output collapses linearly with input.

Can LD39115J28R be used with a 0.47 µF output capacitor instead of the specified 1 µF?

No. ST specifies 1 µF minimum ceramic COUT for stability across temperature and load. Using 0.47 µF risks oscillation due to insufficient phase margin, especially at high temperatures or light loads. The datasheet's stability zone chart (Fig. 35) confirms instability below 0.8 µF for typical PCB layouts.

How does the enable pin behave during power-up when VIN ramps slowly?

The EN pin has hysteresis: turn-on threshold is 1.48 V (typ.), turn-off is 1.35 V (typ.). If VIN rises slowly while EN is held high, the device activates once VIN exceeds ~1.48 V and remains on until VIN drops below 1.35 V. No external pull-up is needed-the internal EN bias ensures defined state during undervoltage.

Is LD39115J28R compliant with AEC-Q200 for automotive applications?

LD39115J28R is not AEC-Q200 qualified. While it operates from -40 °C to +125 °C and includes thermal shutdown, ST does not list it in their AEC-Q200 product matrix. For automotive cabin or engine bay use, select the AEC-Q200 qualified LD39115J variant with "Q" suffix (e.g., LD39115J28RQ) which undergoes stress testing per the standard.