Texas Instruments LMS3655MMRNLT

Overview

LMS3655MMRNLT from Texas Instruments is a 5.5-A, 36-V synchronous step-down DC-DC converter in a 4-mm × 5-mm VQFN-HR package, delivering adjustable 1-V to 20-V output with ±1.5% reference voltage tolerance, 400-kHz fixed switching frequency (±10%), and 96% peak efficiency at 12-V input to 5-V output-used in telecom power supplies and industrial control modules requiring high efficiency and low EMI.

For engineers reviewing the LMS3655MMRNLT datasheet, LMS3655MMRNLT pinout, LMS3655MMRNLT application, or LMS3655MMRNLT equivalent, key selection considerations include its pseudo-random spread-spectrum operation for EMI reduction, open-drain RESET output with 3-ms release timer and internal filtering, automatic light-load mode versus pin-selectable forced PWM mode, and 32-µA quiescent current at 3.3-V output with no load.

Technical Context

The LMS3655MMRNLT employs peak current mode control with frequency foldback architecture to maintain regulation down to 3.5-V input at 3.3-V output, enabling 98% maximum duty cycle and 650-mV dropout capability. Its flip-chip HotRod™ packaging minimizes parasitic inductance and reduces switch-node ringing.

It integrates internal compensation, soft-start, thermal shutdown, UVLO, and current limiting. The device supports external synchronization (250–500 kHz), features dual power-ground pins (PGND1/PGND2) tied together on PCB, and uses BIAS pin connection to output for auxiliary bias regulation-critical for stable operation above 15-V output.

Key Specifications

Pinout & Package

Package: VQFN-HR (22-pin), 4.00 mm × 5.00 mm, 0.5-mm pitch, wettable flanks for optical solder inspection.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM61480RQR and TPS54561RGTR, the LMS3655MMRNLT uniquely combines spread-spectrum EMI reduction, integrated open-drain RESET with filtering, and 4-mm × 5-mm wettable-flank packaging-making it optimal for noise-sensitive, safety-critical industrial and medical applications where component count and reliability are prioritized over raw switching speed or extreme input voltage range.

Availability

LMS3655MMRNLT is available at Aetrix Electronics and suitable for telecom infrastructure, medical instrumentation, and industrial PLC applications requiring stable component supply, long-term lifecycle assurance, and traceable sourcing from authorized channels.

Supply support for LMS3655MMRNLT 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, embedded processing, and power management technologies, with decades of expertise in high-reliability power conversion ICs.

The LMS3655 product line targets high-performance industrial and medical applications demanding low EMI, wide input range, and integrated supervision-designed to replace multi-component power solutions with single-chip reliability.

FAQ

What is the minimum input voltage required for LMS3655MMRNLT to regulate a 3.3-V output at full 5.5-A load?

The LMS3655MMRNLT requires a minimum input voltage of 3.8 V after start-up to maintain regulation accuracy at 5.5-A load with 3.3-V output. This is enabled by its frequency foldback architecture and 98% maximum duty cycle, allowing operation within 650-mV VIN–VOUT differential. Below this, dropout behavior occurs with reduced output accuracy.

Does LMS3655MMRNLT support external clock synchronization, and what is the valid frequency range?

Yes, the LMS3655MMRNLT supports external clock synchronization via the SYNC pin, accepting input frequencies from 250 kHz to 500 kHz with 25%–75% duty cycle. This allows precise timing alignment with system clocks in multi-rail power architectures, reducing beat-frequency noise in synchronized converter arrays.

How does the RESET output of LMS3655MMRNLT behave when the EN pin is pulled low?

When EN is pulled low, the LMS3655MMRNLT forces the open-drain RESET output low regardless of output voltage status. This provides a deterministic system reset signal during controlled shutdown. RESET remains functional down to 1.5-V input voltage, after which it enters high-impedance state-ensuring reliable sequencing in brown-out conditions.

Can LMS3655MMRNLT operate with output voltages above 15 V, and what is required?

Yes, the LMS3655MMRNLT supports output voltages up to 20 V, but operation above 15 V requires the BIAS pin to be grounded or powered by an external source-since internal bias regulation is disabled above that threshold. This prevents overstress on the BIAS pin, which has a 16-V absolute maximum rating.

What thermal metrics define the LMS3655MMRNLT's thermal performance on a standard PCB?

On a thermally optimized 4-layer FR4 PCB, the LMS3655MMRNLT achieves a junction-to-ambient thermal resistance (RθJA) of 29.4°C/W and junction-to-board (RθJB) of 5.4°C/W. These values enable 5.5-A continuous operation at 85°C ambient without forced airflow-validated per JEDEC JESD51 standards using industry-standard test boards.