STMicroelectronics LDQ40PUR

Overview

LDQ40PUR from STMicroelectronics is an AEC-Q100 Grade 1 qualified adjustable-output low-dropout linear regulator delivering 250 mA with ±1.5% output voltage accuracy over temperature, 500 mV typical dropout at full load, and 2 µA typical quiescent current. It operates from 3.3 V to 40 V input and supports remote sensing via the ADJ/VSENSE pin - ideal for automotive always-on battery-connected systems requiring high reliability under -40 °C to 150 °C junction conditions.

For engineers reviewing the LDQ40PUR datasheet, LDQ40PUR pinout, LDQ40PUR application, or LDQ40PUR equivalent, this page delivers verified technical context, package-specific pin functions, real-world automotive use cases, and validated alternative LDOs with documented functional trade-offs in thermal performance, enable logic behavior, and Power Good implementation.

Technical Context

The LDQ40PUR uses a P-channel MOSFET pass element enabling ultra-low dropout and stable operation with ceramic output capacitors as small as 1 µF. Its internal bandgap reference and error amplifier maintain tight regulation across wide input (3.3–40 V) and load (1–250 mA) ranges while supporting remote voltage sensing through the ADJ/VSENSE pin.

Thermal shutdown activates at 170 °C with 20 °C hysteresis; short-circuit protection limits output current to 65–250 mA depending on temperature; and the open-drain Power Good output asserts low when VOUT falls below 93% of nominal. The device integrates active output discharge (RON ≈ 70 Ω) and logic-controlled shutdown with sub-0.3 µA standby current.

Key Specifications

Pinout & Package

LDQ40PUR is supplied in DFN 2×2 mm 6-lead wettable flanks (WF) package - optimized for automated optical inspection (AOI) and high-reliability automotive solder joints. Exposed pad must be connected to GND for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLE42754G and NCP1117ST50T3G, LDQ40PUR uniquely combines AEC-Q100 Grade 1 compliance, adjustable output with remote sensing, wettable flanks for automotive AOI, and integrated Power Good - making it the only choice for new-design automotive LDOs requiring functional safety alignment and production-grade manufacturability.

Availability

LDQ40PUR is available at Aetrix Electronics and suitable for EV powertrain control units, ADAS radar modules, and automotive instrument clusters requiring stable component supply with full automotive qualification and traceable sourcing.

Supply support for LDQ40PUR 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 LDQ40 series belongs to ST's automotive-grade power management portfolio, engineered specifically for always-on, high-reliability battery-connected applications in electric vehicles and advanced driver-assistance systems.

FAQ

What is the minimum input voltage required for LDQ40PUR to regulate stably?

The LDQ40PUR requires VIN ≥ VOUT(NOM) + VDROP to maintain regulation. With 500 mV typical dropout at 250 mA, a 3.3 V output needs ≥3.8 V input. However, the internal UVLO disables operation below 2.65 V (rising), so stable regulation begins at ~3.0 V for low-VOUT configurations - confirmed by DS13774 Figure 7 and Table 6.

Can LDQ40PUR be used with ceramic output capacitors smaller than 1 µF?

No. ST specifies a minimum 1 µF X5R/X7R ceramic capacitor on the output for loop stability (DS13774 Section 6.6). Using smaller values risks oscillation or poor transient response, especially under load steps. The control architecture is optimized for 1–200 µF range with 5–10 Ω ESR - verified in stability testing per JEDEC JESD78.

How does the Power Good (PG) pin behave during thermal shutdown?

During thermal shutdown, the LDQ40PUR disables the pass transistor and pulls PG low - consistent with its specification as "low when VOUT is below minimum PG threshold" (DS13774 Table 6). This behavior provides unambiguous fault signaling to host controllers, eliminating ambiguity between undervoltage and overtemperature events.

Is the ADJ pin internally biased, and what is its leakage current?

Yes, the ADJ pin has an internal 1.2 V reference with 0.1–0.5 µA operating current (DS13774 Table 6). This low bias current enables high-value resistor dividers (up to 2 MΩ) for precision output setting while minimizing power loss - critical for battery-operated ADAS sensors where divider current must stay below 1 µA.