STMicroelectronics LDH40MR

Overview

LDH40MR from STMicroelectronics is an AEC-Q100 Grade 1 qualified adjustable low-dropout linear regulator (LDO) for automotive and industrial battery-connected systems. It delivers 200 mA output current with 700 mV typical dropout at full load, 0.5% output voltage accuracy at 25 °C, and ultra-low 2 µA quiescent current at no load - enabling reliable operation in always-on standby applications such as body control modules and ADAS power rails.

For engineers reviewing the LDH40MR datasheet, LDH40MR pinout, LDH40MR application, or LDH40MR equivalent, key selection criteria include its 3.3–40 V input range, ADJ-pin-based 1.2–22 V output configurability, Power Good (PG) signal availability (SOT23-5L variant), logic-controlled shutdown (<0.3 µA off-state current), and thermal/overcurrent protection - all in a compact SOT23-5L package rated for −40 °C to +150 °C junction temperature.

Technical Context

The LDH40MR implements a P-channel MOSFET pass element with internal bandgap reference and error amplifier for high-accuracy output regulation. Its adjustable architecture uses the ADJ pin with external resistor divider to set output voltage from 1.2 V to 22 V, supporting remote sensing and precise voltage tailoring across wide load and temperature ranges.

It integrates multiple system-level protections: thermal shutdown at 175 °C (20 °C hysteresis), internal current limiting (350–1000 mA depending on conditions), open-drain Power Good monitoring (93–98% VOUT threshold), and active output discharge via internal 150 Ω MOSFET when EN is deasserted - critical for safe power sequencing in automotive ECUs.

Key Specifications

Pinout & Package

LDH40MR is supplied in SOT23-5L package (2.92 mm × 2.80 mm × 1.10 mm), optimized for space-constrained automotive PCBs and compatible with standard reflow processes. The exposed pad is absent in this variant (unlike DFN WF versions), simplifying layout while maintaining thermal performance via PCB copper area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7B8750QKVURQ1 and NCP163AMX330TBG, LDH40MR uniquely combines adjustability (1.2–22 V), integrated PG, ultra-low IQ, and AEC-Q100 Grade 1 qualification - making it the only option suitable for safety-critical, multi-rail automotive subsystems requiring programmable voltage and power integrity monitoring.

Availability

LDH40MR is available at Aetrix Electronics and suitable for automotive body control modules, ADAS camera power supplies, and always-on telematics gateways requiring stable component supply across long product lifecycles and harsh environmental conditions.

Supply support for LDH40MR 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.

LDH40MR belongs to ST's automotive-grade LDO portfolio, engineered specifically for direct battery connection in 12 V/24 V vehicles - emphasizing ultra-low IQ, extended temperature operation, and functional safety readiness for ASIL-B–compatible systems.

FAQ

What is the minimum input voltage required for LDH40MR to regulate at 3.3 V output?

The LDH40MR requires VIN ≥ VOUT(NOM) + VDROP to maintain regulation. At 200 mA load and 3.3 V output, typical dropout is 700 mV, so minimum VIN is 4.0 V. However, the device can start up and regulate down to 3.3 V input under light loads due to its low-RDS(on) P-MOSFET architecture - confirmed by electrical characteristics table showing VIN operating range starting at VOUT + VDROP (min 3.3 V).

Does LDH40MR support remote voltage sensing, and how is it implemented?

Yes - LDH40MR supports remote sensing via its ADJ pin. By routing the ADJ node to the load-side of the output trace (rather than directly to VOUT pin), the regulator compensates for IR drop across PCB traces or connectors. This requires connecting R1 between VOUT and ADJ, and R2 between ADJ and GND, per VOUT = (1 + R1/R2) × 1.2 V, with IADJ ≤ 0.5 µA ensuring minimal divider error.

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

PG is an open-drain output that remains high-impedance (Hi-Z) when EN is low or when VOUT is within valid range. It pulls low only when VOUT falls below 93–98% of nominal value. During startup, PG asserts high after VOUT reaches regulation and stabilizes; during shutdown, PG goes Hi-Z immediately upon EN deassertion - providing unambiguous power status without delay or glitch.

Can LDH40MR be used with ceramic output capacitors smaller than 1 µF?

No - the datasheet specifies a minimum 1.0 µF ceramic output capacitor (X5R/X7R) for guaranteed loop stability across temperature, load, and input voltage ranges. Using smaller values risks oscillation or poor transient response, especially under fast load steps. ESR must remain between 5 mΩ and 10 Ω; X5R/X7R types are recommended to maintain stable capacitance and ESR over −40 °C to +125 °C.