STMicroelectronics LD39115J18R

Overview

LD39115J18R from STMicroelectronics is a 150 mA ultra-low-noise, low-quiescent-current LDO voltage regulator delivering a fixed 1.8 V output with ±2.0 % tolerance at 25 °C. It operates from 1.5 V to 5.5 V input, achieves 80 mV typical dropout at 100 mA, and consumes only 20 µA quiescent current at no load-enabling long battery life in portable power rails for microcontrollers and RF subsystems.

For engineers reviewing the LD39115J18R datasheet, LD39115J18R pinout, LD39115J18R application, or LD39115J18R equivalent, key selection criteria include its 33 µV_RMS noise (1 kHz–100 kHz), logic-controlled shutdown (<1 µA off-mode current), ceramic capacitor compatibility (1 µF C_OUT), thermal/short-circuit protection, and operation across –40 °C to 125 °C junction temperature.

Technical Context

The LD39115J18R uses a bandgap-referenced feedback loop with internal trimming to maintain 1.8 V output accuracy. Its flip-chip 4-bump construction enables compact layout and low parasitic inductance, critical for noise-sensitive analog and RF supply domains.

Enable control is implemented as a CMOS-compatible logic input (EN pin), with guaranteed low-level threshold ≤0.4 V and high-level threshold ≥0.9 V over full temperature range. Internal current limiting and thermal shutdown activate at 160 °C with 20 °C hysteresis, ensuring robust fault handling without external components.

Key Specifications

Pinout & Package

LD39115J18R uses a flip-chip 4-bump package (0.8 mm × 0.8 mm, 0.4 mm pitch), optimized for minimal footprint and thermal resistance (R_thJA = 180 °C/W). The bump layout supports standard PCB assembly with solder paste printing and reflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6210B182MR-G and RT9013-18GB, LD39115J18R offers the lowest noise and dropout among the three, making it optimal for space-constrained, battery-limited, noise-critical applications where 150 mA suffices.

Availability

LD39115J18R is available at Aetrix Electronics and suitable for mobile phone power management, wearable sensor hub supply, industrial IoT edge node design, and automotive body control module development requiring stable component supply across production lifecycles.

Supply support for LD39115J18R 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 designing and manufacturing silicon solutions for automotive, industrial, and consumer markets, with R&D centers across Europe, Asia, and the Americas.

The LD39115J series belongs to ST's high-performance analog LDO portfolio, engineered specifically for ultra-low-noise, low-I_Q power delivery in portable and battery-operated systems demanding extended runtime and signal integrity.

FAQ

What is the minimum input voltage required for LD39115J18R to regulate 1.8 V output?

The LD39115J18R requires a minimum input voltage of 1.5 V to operate, but to maintain regulation at full 150 mA load, the input must exceed 1.8 V + dropout voltage. With 80 mV typical dropout at 100 mA and 110 mV max over temperature, a safe minimum is 1.92 V at room temperature and 1.95 V across full temperature range.

Can LD39115J18R be used with a 1 µF ceramic output capacitor only?

Yes - the LD39115J18R is explicitly designed for stability with a single 1 µF ceramic capacitor (X5R/X7R) on the output, as confirmed in Section 3 (Typical Application) and Table 5 of the datasheet. No additional bulk capacitance or ESR tuning is required for stable operation.

Does LD39115J18R include reverse polarity or reverse current protection?

No - the LD39115J18R does not integrate reverse polarity or reverse current protection. It lacks internal body-diode blocking or dedicated reverse-voltage clamping. External protection (e.g., series Schottky diode or ideal diode controller) is required if the output may exceed the input voltage during fault or power-down sequences.

How does the enable pin behave during power-up sequencing?

The EN pin has a guaranteed logic-low threshold ≤0.4 V and logic-high threshold ≥0.9 V across –40 °C to 125 °C. Turn-on time is 30 µs (time from EN crossing 0.9 V to V_OUT reaching 95 % of 1.8 V), enabling tight synchronization with system reset controllers without external timing components.