STMicroelectronics LD39100PU12R

Overview

LD39100PU12R from STMicroelectronics is a 1 A, ultra-low-dropout linear regulator in DFN6 (3×3 mm) package with fixed 1.2 V output, AEC-Q100 qualified for automotive post-regulation. It delivers 200 mV typical dropout at 1 A, 20 µA quiescent current at no load, ±2.0% output voltage tolerance at 25 °C, and operates from 1.5 V to 5.5 V input across –40 °C to 125 °C. Used in automotive infotainment power rails requiring low-noise, low-quiescent-current regulation.

For engineers reviewing the LD39100PU12R datasheet, LD39100PU12R pinout, LD39100PU12R application, or LD39100PU12R equivalent, key selection criteria include dropout voltage at 1 A load, PG threshold behavior, EN logic compatibility with 0.4 V/0.9 V thresholds, thermal shutdown hysteresis (20 °C), and stability with 1 µF ceramic output capacitor - all confirmed in DS6257 Rev 9.

Technical Context

The LD39100PU12R implements a PMOS pass transistor architecture enabling ultra-low dropout and near-zero reverse current during shutdown. Its bandgap reference feeds an error amplifier driving the pass element, with internal current limiting and thermal foldback activating at 160 °C junction temperature and releasing at 140 °C.

It integrates a dedicated open-drain Power Good (PG) output referenced to 0.92×VOUT (rising) and 0.80×VOUT (falling), requiring external pull-up (100 kΩ–1 MΩ). The enable input accepts standard CMOS logic levels (VIH = 0.9 V, VIL = 0.4 V) with <100 nA input current and supports <1 µA off-mode supply current.

Key Specifications

Pinout & Package

LD39100PU12R uses the DFN6 (3×3 mm) wettable flank package with exposed thermal pad connected to GND. Pin 1 is EN, Pin 2 is GND, Pin 3 is PG, Pin 4 is VOUT, Pin 5 is NC (no connection), Pin 6 is VIN. The exposed pad must be soldered to a GND copper pour for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6210B122MR-G and ADP1740ACPZ-1.2-R7, the LD39100PU12R uniquely combines AEC-Q100 Grade 1 compliance, sub-µA shutdown, integrated temperature-compensated PG, and 55 °C/W thermal resistance - making it the sole choice for automotive-grade 1.2 V post-regulation where reliability, low power, and functional safety signaling are co-required.

Availability

LD39100PU12R is available at Aetrix Electronics and suitable for automotive infotainment systems, ADAS camera modules, and industrial PLC I/O modules requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for LD39100PU12R 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 power management applications.

The LD39100 belongs to ST's high-reliability automotive LDO portfolio, engineered specifically for post-regulation in demanding environments where low noise, ultra-low IQ, and AEC-Q100 compliance are mandatory design requirements.

FAQ

What is the minimum input voltage required for stable 1.2 V output at 1 A load?

The LD39100PU12R requires VIN ≥ 1.4 V to maintain regulation at 1 A, based on its 200 mV typical dropout voltage. At –40 °C to +125 °C, maximum dropout rises to 400 mV, so VIN must be ≥ 1.6 V across full temperature range. Input below 1.5 V is outside absolute maximum rating and risks functional failure.

Can the PG pin be left unconnected if not used in the design?

Yes - the PG pin must remain floating if unused. It is an open-drain output requiring external pull-up only when active. Leaving it unconnected avoids unintended current paths or noise injection; connecting it to GND or VOUT would disable the flag or cause excessive leakage.

Is the LD39100PU12R stable with a 2.2 µF X7R ceramic output capacitor?

Yes - the device is characterized stable with 1–100 µF ceramic capacitors having ESR between 0–150 mΩ. A 2.2 µF X7R capacitor meets both capacitance and ESR requirements across –40 °C to +125 °C, and improves transient response versus the minimum 1 µF value.

Does the EN pin have internal pull-up or pull-down resistors?

No - the EN pin has no internal pull-up or pull-down. It must be actively driven by a GPIO or resistor divider; leaving it floating may cause undefined operation or erratic enable/disable behavior due to noise susceptibility and lack of bias.