Analog Devices Inc. LTC3851AMPMSE#PBF

Overview

LTC3851AMPMSE#PBF from Analog Devices (formerly Linear Technology) is a high-performance synchronous step-down switching regulator controller driving dual N-channel MOSFETs in a constant-frequency current-mode architecture. It operates from 4V to 38V input, delivers 0.8V–5.5V output with ±1% accuracy, supports phase-lockable 250kHz–750kHz switching, and features OPTI-LOOP® compensation for transient optimization-used in automotive power supplies requiring wide temperature operation and robust overvoltage protection.

For engineers reviewing the LTC3851AMPMSE#PBF datasheet, LTC3851AMPMSE#PBF pinout, LTC3851AMPMSE#PBF application, or LTC3851AMPMSE#PBF equivalent, key selection criteria include its –55°C to 150°C MP-grade thermal rating, RSENSE/DCR current sensing flexibility, selectable light-load modes (Burst/Pulse-Skipping/CCM), and integrated 5V INTVCC regulator with 50mA peak drive capability.

Technical Context

The LTC3851AMPMSE#PBF implements a constant-frequency current-mode control loop where the ITH pin voltage sets peak inductor current via an error amplifier with 2mmho transconductance and 3MHz gain-bandwidth. Its phase-locked loop accepts external clocks (250–750kHz) on MODE/PLLIN and uses FREQ/PLLFLTR as PLL filter node or frequency-setting resistor connection point.

It integrates dual gate drivers (TG/BG) with matched 25ns rise/fall times, 30ns dead-time control, and low on-resistance (TG RUP = 2.2Ω, BG RDOWN = 1.1Ω). The controller supports output tracking via TK/SS pin with 1µA soft-start current, and includes dedicated overvoltage lockout (7.5–12.5% above VFB) and current foldback limiting activated by ILIM pin configuration.

Key Specifications

Pinout & Package

Package: 16-lead plastic MSOP (MSE) with exposed thermal pad (Pin 17 = GND), rated for –55°C to 150°C operating junction temperature and θJA = 40°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3851AIMSE#PBF and LTC3851AEMSE#PBF, the LTC3851AMPMSE#PBF uniquely guarantees full electrical performance across –55°C to 150°C, making it the sole option for aerospace, defense, and under-hood automotive designs where extreme thermal resilience is mandatory.

Availability

LTC3851AMPMSE#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial programmable logic controllers, and telecom base station power supplies requiring stable component supply across extended temperature extremes and long production lifecycles.

Supply support for LTC3851AMPMSE#PBF 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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.

The LTC3851A product line delivers high-efficiency, wide-input synchronous buck controllers optimized for demanding industrial, automotive, and telecom power systems where precision, reliability, and thermal resilience are critical.

FAQ

What is the operating temperature range guaranteed for the LTC3851AMPMSE#PBF?

The LTC3851AMPMSE#PBF is tested and guaranteed over a junction temperature range of –55°C to 150°C. This MP-grade specification ensures full electrical performance-including ±1% output voltage accuracy, current sense threshold stability, and gate driver timing-across this entire range, unlike I-grade (–40°C to 125°C) or E-grade (0°C to 85°C) variants of the LTC3851A.

How does the ILIM pin configure current limiting on the LTC3851AMPMSE#PBF?

The ILIM pin on the LTC3851AMPMSE#PBF selects one of three maximum current sense thresholds: 30mV (ILIM = GND), 50mV (ILIM = floating), or 75mV (ILIM = INTVCC). This tri-level configuration directly sets the peak inductor current limit without external resistors, enabling precise MOSFET SOA protection tailored to RSENSE value or DCR-based sensing networks.

Can the LTC3851AMPMSE#PBF synchronize to an external clock, and what are the requirements?

Yes, the LTC3851AMPMSE#PBF can synchronize its internal oscillator to an external clock applied to the MODE/PLLIN pin. The external clock must be 250kHz–750kHz, and a series RC network must be connected between FREQ/PLLFLTR and GND to serve as the PLL loop filter. The external clock should be present before enabling RUN to avoid low-frequency startup anomalies.

What is the purpose of the TK/SS pin on the LTC3851AMPMSE#PBF, and how is it used?

The TK/SS pin on the LTC3851AMPMSE#PBF serves dual functions: soft-start control and output voltage tracking. An external capacitor to GND creates a linear voltage ramp (charged by internal 1µA current), enabling controlled VOUT rise. Alternatively, connecting a resistor divider from a master supply to TK/SS achieves ratiometric or coincident tracking-critical for multi-rail sequencing in FPGAs and processors.

Does the LTC3851AMPMSE#PBF include overvoltage protection, and how does it operate?

Yes, the LTC3851AMPMSE#PBF includes dedicated output overvoltage protection (OVP) that triggers when VFB exceeds the regulated setpoint by 7.5–12.5%. Upon detection, the top MOSFET is immediately turned off and the bottom MOSFET is turned on to clamp VOUT, preventing damage to downstream loads. This OVP is independent of the main control loop and responds within nanoseconds.