STMicroelectronics LDQ40PU50RY

Overview

LDQ40PU50RY from STMicroelectronics is a 5.0 V fixed-output, AEC-Q100 Grade 1 qualified low-dropout linear regulator delivering 250 mA with 500 mV typical dropout at full load, ±1.5% output voltage tolerance over -40 °C to 150 °C, and 2 µA typical quiescent current at no load - deployed in automotive infotainment power rails and ADAS always-on domains.

For engineers reviewing the LDQ40PU50RY datasheet, LDQ40PU50RY pinout, LDQ40PU50RY application, or LDQ40PU50RY equivalent, key selection criteria include Power Good signaling, wettable-flank DFN2x2-6L package compatibility for automated optical inspection, thermal shutdown at 170 °C, and adjustable discharge MOSFET (70 Ω) for controlled output ramp-down.

Technical Context

The LDQ40PU50RY integrates a P-channel MOSFET pass element enabling operation down to 3.3 V input while maintaining regulation up to 40 V. Its bandgap reference and error amplifier deliver high DC accuracy (±0.5% at 25 °C) and tight load/line regulation (≤3.0 mV, ≤0.05 %/V).

It features dual protection architecture: current limiting (350–1000 mA) triggered at 90% VOUT(NOM), and short-circuit protection clamping output current to 65–250 mA when VOUT drops below 0.4 V. The Power Good open-drain output asserts high when VOUT reaches ≥93% of nominal and deasserts at ≤95% with 30–70 mV hysteresis.

Key Specifications

Pinout & Package

LDQ40PU50RY uses the DFN 2x2 mm 6-lead wettable flanks (WF) package - optimized for automated optical inspection (AOI) and high-reliability solder joint formation in automotive PCB assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output LDO applications.

Compared with TLE42754G and NCP115ASN50T2G, LDQ40PU50RY uniquely combines AEC-Q100 Grade 1 qualification, wettable flanks for AOI, integrated Power Good, and 70 Ω output discharge - making it the only option meeting full ASIL-B supporting power rail requirements in modern automotive ECUs.

Availability

LDQ40PU50RY is available at Aetrix Electronics and suitable for automotive infotainment systems, ADAS camera modules, instrument clusters, and body control units requiring stable component supply with full AEC-Q100 traceability and long-term lifecycle support.

Supply support for LDQ40PU50RY 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 specializing in automotive, industrial, and power management ICs, with manufacturing aligned to IATF 16949 and environmental standards including ECOPACK®.

LDQ40PU50RY belongs to ST's automotive-grade LDO family designed specifically for always-on, low-quiescent-current power rails in EV powertrain and ADAS subsystems - emphasizing thermal resilience, functional safety readiness, and AOI-compatible packaging.

FAQ

What is the minimum input voltage required for regulation at 5.0 V output?

The LDQ40PU50RY requires VIN ≥ VOUT + VDROP to maintain regulation. With 500 mV typical dropout at 250 mA, the minimum input is 5.5 V. However, undervoltage lockout releases at 2.65 V, so the device powers up only when VIN exceeds this threshold - ensuring stable start-up even with weak batteries.

Can the LDQ40PU50RY be used with ceramic output capacitors below 1 µF?

No. The datasheet specifies a minimum 1.0 µF ceramic output capacitor (X5R/X7R) with ESR between 5 mΩ and 10 Ω for guaranteed loop stability. Using smaller values risks oscillation or poor transient response, especially under load steps common in automotive microcontroller applications.

How does the Power Good (PG) pin behave during enable/disable transitions?

PG is high-impedance when EN = LOW (shutdown mode) or when VOUT is within 93–98% of 5.0 V. It pulls low only when VOUT falls below 95% of nominal during faults or startup. There is no delay or filtering - PG responds within microseconds to output voltage deviations, enabling fast system-level fault detection.

Is the exposed pad electrically connected, and how must it be handled on the PCB?

Yes, the exposed pad is internally connected to GND and must be soldered to a dedicated PCB ground plane using ≥4 thermal vias. This connection is mandatory for achieving the specified R_thJA = 62 °C/W and preventing thermal shutdown under 250 mA continuous load - floating or unconnected pads cause immediate thermal violation.