Analog Devices Inc. LTC3646HMSE#TRPBF

Overview

LTC3646HMSE#TRPBF from Analog Devices (formerly Linear Technology) is a 40V input, 1A synchronous step-down DC/DC converter with integrated high-side and synchronous power FETs. It delivers ±1% output voltage accuracy, operates from 4.0V to 40V input, supports 2.0V–30V output range, achieves up to 95% efficiency, and draws only 140µA quiescent current in Burst Mode at no load - ideal for high-voltage industrial point-of-load supplies.

For engineers reviewing the LTC3646HMSE#TRPBF datasheet, LTC3646HMSE#TRPBF pinout, LTC3646HMSE#TRPBF application, or LTC3646HMSE#TRPBF equivalent, key selection criteria include its 150°C junction-rated MSOP-16 package, programmable 200kHz–3MHz switching frequency, controlled on-time architecture enabling large step-down ratios, and support for both Burst Mode and forced continuous operation.

Technical Context

The LTC3646HMSE#TRPBF implements a current-mode, monolithic synchronous buck topology with patented controlled on-time architecture. Its valley-current sensing and internal 0.6V reference enable stable regulation across wide VIN/VOUT ratios without output overvoltage risk, even at 40V input stepping down to 2V output.

It integrates dual power MOSFETs (200mΩ high-side, 120mΩ low-side), a 5.0V INTVCC regulator, PGOOD monitoring with 7.5% threshold window, and robust protection including SVIN/PVIN overvoltage lockout (43.5V trip), short-circuit current limiting (1.2A typ), and thermal shutdown. The MODE/SYNC pin enables mode selection or external clock synchronization.

Key Specifications

Pinout & Package

Package: 16-Lead Plastic MSOP with exposed thermal pad (Pin 17 = PGND). Designed for high thermal performance (θJA = 38°C/W) in space-constrained industrial and automotive PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5164QPWPRQ1 and MP2451DT-LF-Z, the LTC3646HMSE#TRPBF uniquely combines 40V input, 1A output, 150°C rating, Burst Mode, PGOOD, and programmable frequency - making it the only option meeting full industrial and extended-temperature requirements without compromise.

Availability

LTC3646HMSE#TRPBF is available at Aetrix Electronics and suitable for industrial PLCs, automotive body control units, and medical sensor hubs requiring stable component supply with long lifecycle assurance and traceable sourcing.

Supply support for LTC3646HMSE#TRPBF 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

Analog Devices (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LTC3646 belongs to Linear's high-voltage monolithic buck regulator product line, designed specifically for robust, high-efficiency point-of-load conversion in harsh environments - emphasizing wide VIN, thermal resilience, and protection integrity.

FAQ

What is the maximum input voltage rating for the LTC3646HMSE#TRPBF?

The LTC3646HMSE#TRPBF has an absolute maximum PVIN/SVIN rating of 45V, with overvoltage lockout triggered at 43.5V (typical). Its operational input range is specified from 4.0V to 40V, making it suitable for 24V and 36V industrial buses and automotive systems subject to load-dump transients. Exceeding 40V continuously may trigger protection or reduce lifetime.

Does the LTC3646HMSE#TRPBF support output voltages below 2.0V?

No - the LTC3646HMSE#TRPBF variant is specified for 2.0V to 30V output. For sub-2.0V outputs (down to 0.6V), the pin-compatible LTC3646-1 family (e.g., LTC3646HMSE-1#TRPBF) must be used. The -1 suffix denotes the alternate feedback range; mixing variants risks incorrect regulation or instability.

How does the controlled on-time architecture benefit the LTC3646HMSE#TRPBF in high step-down applications?

The controlled on-time architecture in the LTC3646HMSE#TRPBF calculates switch on-time based on VON/VIN ratio and target frequency, ensuring stable regulation even at extreme step-down ratios (e.g., 40V→2V). Unlike voltage-mode or traditional current-mode controllers, it avoids subharmonic oscillation and output overvoltage during startup or line transients - critical for reliability in high-VIN systems.

Can the LTC3646HMSE#TRPBF be synchronized to an external clock, and what are the requirements?

Yes - the MODE/SYNC pin accepts an external clock signal (0.2MHz–3.0MHz) to synchronize switching. When driven externally, the LTC3646HMSE#TRPBF operates in forced continuous mode. An RT resistor matching the clock frequency must be installed (e.g., 60kΩ for 2.25MHz); floating RT is not allowed. Clock duty cycle should be 40–60% for reliable locking.

What thermal considerations apply to the LTC3646HMSE#TRPBF in its MSOP-16 package?

The LTC3646HMSE#TRPBF uses a thermally enhanced MSOP-16 with exposed PGND pad (Pin 17), rated for θJA = 38°C/W. To achieve 150°C junction operation at full 1A load, the PCB must provide ≥4 cm² of 2-oz copper connected to the exposed pad, with ≥6 thermal vias. Without proper thermal design, power dissipation will limit usable output current well below 1A at elevated ambient temperatures.