Texas Instruments LMR36503MSC3RPERQ1

Overview

LMR36503MSC3RPERQ1 from Texas Instruments is an AEC-Q100 Grade 1 automotive-grade synchronous buck converter delivering 0.3 A at fixed 3.3 V output, operating from 3.0 V to 65 V input, featuring 4 µA quiescent current in switching mode (VIN = 24 V → VOUT = 3.3 V), 2.2 MHz fixed switching frequency, and integrated PGOOD flag. It serves as a primary power supply for low-power ADAS sensors and infotainment subsystems requiring cold-crank resilience.

For engineers reviewing the LMR36503MSC3RPERQ1 datasheet, LMR36503MSC3RPERQ1 pinout, LMR36503MSC3RPERQ1 application, or LMR36503MSC3RPERQ1 equivalent, key selection considerations include its 2-mm × 2-mm HotRod™ VQFN-HR package with wettable flanks, -40°C to +125°C ambient temperature rating, pseudo-random spread spectrum EMI compliance per CISPR 25, and seamless FPWM-to-PFM transition for ultra-low-load efficiency.

Technical Context

The LMR36503MSC3RPERQ1 employs peak current mode control with internal compensation, enabling stable regulation with minimal external output capacitance. Its architecture supports automatic frequency foldback during deep input sags-maintaining regulation down to 2.45 V VIN (falling threshold)-and integrates a precision enable comparator with 0.35 V hysteresis for robust cold-crank start-up sequencing.

It features a dedicated MODE/SYNC pin for external clock synchronization (0.2–2.2 MHz), a PGOOD open-drain flag with 1.8% hysteresis and 1.96 ms activation delay, and thermal shutdown with 168°C trip and 158°C recovery thresholds. The device uses integrated high- and low-side MOSFETs (RDS(on) = 920 mΩ / 460 mΩ) and includes CBOOT UVLO protection at 2.3 V.

Key Specifications

Pinout & Package

VQFN-HR (RPE) 9-pin, 2.0 mm × 2.0 mm package with wettable flanks and corner anchor pins for reliable reflow soldering and automated optical inspection.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck converter applications.

Compared with LMR36503MSC5RPERQ1, the LMR36503MSC3RPERQ1 offers tighter voltage matching for 3.3 V I/O domains; versus LMR36506MSC3RPERQ1, it provides lower conduction loss at light loads and smaller thermal footprint for space-constrained modules.

Availability

LMR36503MSC3RPERQ1 is available at Aetrix Electronics and suitable for advanced driver assistance systems (ADAS), body electronics and lighting, and infotainment and cluster applications requiring stable component supply across automotive production lifecycles.

Supply support for LMR36503MSC3RPERQ1 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

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of automotive qualification expertise and functional safety documentation support.

The LMR36503-Q1 product line delivers compact, high-efficiency DC/DC conversion for automotive subsystems demanding AEC-Q100 Grade 1 reliability, cold-crank resilience, and CISPR 25-compliant EMI performance.

FAQ

What is the maximum input voltage the LMR36503MSC3RPERQ1 can withstand during transients?

The LMR36503MSC3RPERQ1 supports input voltage transients up to 70 V, as specified in its absolute maximum ratings. This enables robust operation during load-dump events in 12-V and 24-V automotive systems. Its recommended operating range starts at 3.0 V (falling threshold) and extends to 65 V, with guaranteed functionality across the full AEC-Q100 Grade 1 ambient temperature range of –40°C to +125°C.

Does the LMR36503MSC3RPERQ1 require external compensation components?

No, the LMR36503MSC3RPERQ1 features internal compensation optimized for stability with minimal output capacitance. This eliminates the need for external Type II or Type III compensation networks, reducing design complexity and BOM count. The device maintains stable regulation across its full 0–0.3 A load range and 3.0–65 V input range using only standard input and output capacitors and a single power inductor.

How does the PGOOD function work on the LMR36503MSC3RPERQ1?

The PGOOD pin on the LMR36503MSC3RPERQ1 is an open-drain flag that asserts high when the 3.3 V output is within ±1.8% of regulation (i.e., 3.24–3.36 V), with a 1.96 ms activation delay after soft-start completion. It goes low when EN is deasserted or VOUT falls outside this window. No external pull-up is mandatory - it can be left floating if unused - and it operates independently of the MODE/SYNC pin configuration.

Can the LMR36503MSC3RPERQ1 be synchronized to an external clock?

Yes, the LMR36503MSC3RPERQ1 supports external clock synchronization via its MODE/SYNC pin. When configured in SYNC mode, it accepts an external clock signal from 0.2 MHz to 2.2 MHz, enabling deterministic switching alignment across multiple converters to reduce beat frequencies and system-level EMI. The pin also allows user-selectable FPWM/PFM operation - no resistor or external circuitry is required for either function.

What is the thermal performance of the LMR36503MSC3RPERQ1 in a typical 4-layer PCB layout?

In a standard 4-layer JEDEC board simulation, the LMR36503MSC3RPERQ1 exhibits a junction-to-ambient thermal resistance (RθJA) of 84.4°C/W and a junction-to-board resistance (RθJB) of 26.1°C/W. Its thermal shutdown activates at 168°C (rising) with 10°C hysteresis, allowing safe operation up to +150°C junction temperature. Layout best practices - including thermal vias under the exposed pad and wide copper pours on inner layers - are essential to achieve these values in production.