Analog Devices Inc. LTC3851EGN#TRPBF

Overview

LTC3851EGN#TRPBF from Analog Devices (formerly Linear Technology) is a high-performance synchronous step-down switching regulator controller driving dual N-channel MOSFETs in constant-frequency current-mode topology. It operates from 4V to 38V input, delivers 0.8V–5.5V output with ±1% reference accuracy, supports phase-lockable 250kHz–750kHz switching, and features OPTI-LOOP® compensation for transient optimization across diverse output capacitance/ESR. It is used in telecom power supplies requiring high efficiency and tight regulation under wide load and input variations.

For engineers reviewing the LTC3851EGN#TRPBF datasheet, LTC3851EGN#TRPBF pinout, LTC3851EGN#TRPBF application, or LTC3851EGN#TRPBF equivalent, key selection criteria include its RSENSE/DCR current sensing flexibility, selectable light-load modes (Burst/Pulse-Skip/CCM), 99% duty cycle capability, integrated 5V INTVCC regulator, and robust overvoltage/overcurrent protection architecture.

Technical Context

The LTC3851EGN#TRPBF implements a constant-frequency current-mode control loop where peak inductor current is set by the ITH voltage, and error amplification is referenced to a precision 0.8V internal bandgap. Its transconductance amplifier (gm = 2 mmho, GBW = 3 MHz) enables stable loop response across broad output capacitor types.

It integrates dual gate drivers (TG/BG) with matched 25ns transition times, programmable current limit via ILIM pin (30/50/75 mV thresholds), and a dedicated phase-locked loop (PLL) interface on MODE/PLLIN and FREQ/PLLFLTR pins for synchronization to external clocks up to 750 kHz.

Key Specifications

Pinout & Package

Package: 16-Lead Plastic Narrow SSOP (GN), RoHS-compliant, thermally enhanced with θJA = 110°C/W. Exposed pad not present in GN package.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous step-down controller applications.

Compared with LTC3851EGN#TRPBF, the LTC3851IGN#TRPBF offers extended temperature operation without electrical or layout changes, while the LTC3851EUD#TRPBF provides superior thermal resistance in a smaller footprint-both retain identical control architecture, pin compatibility, and feature set.

Availability

LTC3851EGN#TRPBF is available at Aetrix Electronics and suitable for telecom power systems, industrial FPGA supplies, and automotive infotainment modules requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LTC3851EGN#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, Inc. (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 LTC3851EGN#TRPBF belongs to Linear's high-efficiency synchronous controller product line, designed specifically for demanding DC-DC conversion in telecom, industrial, and automotive applications where precision, reliability, and thermal resilience are critical.

FAQ

What is the maximum input voltage rating for the LTC3851EGN#TRPBF?

The LTC3851EGN#TRPBF has an absolute maximum input voltage (VIN) rating of 40V, with recommended continuous operation from 4V to 38V. Exceeding 40V risks permanent damage per Absolute Maximum Ratings. The device maintains full functionality-including current sensing, regulation, and protection-across this entire 4V–38V range, making it suitable for unregulated 24V and 48V telecom and industrial bus applications.

How does the ILIM pin configure current limit thresholds on the LTC3851EGN#TRPBF?

The ILIM pin on the LTC3851EGN#TRPBF is a tri-level logic input that selects one of three maximum current sense thresholds: 30mV (ILIM = GND), 50mV (ILIM = floating), or 75mV (ILIM = INTVCC). This directly sets the peak inductor current trip point for foldback limiting and short-circuit protection. The selected threshold determines IMAX based on RSENSE or DCR value, enabling design flexibility for different output current and fault tolerance requirements without changing external components.

Can the LTC3851EGN#TRPBF synchronize to an external clock, and how is it configured?

Yes, the LTC3851EGN#TRPBF can synchronize its internal oscillator to an external clock applied to the MODE/PLLIN pin. To enable PLL mode, a series RC network must be connected between FREQ/PLLFLTR and GND as the loop filter. When an external clock (250–750kHz) is present, the controller locks to it and operates in forced continuous conduction mode. No additional configuration is needed beyond proper RC filter design and clock signal integrity.

What is the purpose of the TK/SS pin on the LTC3851EGN#TRPBF, and how is it used for soft-start?

The TK/SS pin on the LTC3851EGN#TRPBF controls output voltage ramp rate during startup and enables supply tracking. For soft-start, an external capacitor is connected from TK/SS to GND; the internal 1μA current source linearly charges it, causing VOUT to rise proportionally. When TK/SS reaches 0.8V, regulation transitions to the feedback loop. This prevents inrush current and ensures controlled power-up of downstream loads like FPGAs or microprocessors.

Does the LTC3851EGN#TRPBF support both RSENSE and DCR current sensing, and what are the trade-offs?

Yes, the LTC3851EGN#TRPBF supports both discrete RSENSE and inductor DCR current sensing. RSENSE provides higher accuracy and simpler design but adds conduction loss and cost. DCR sensing eliminates the sense resistor, improving efficiency-especially at high currents-but requires careful matching of the RC filter time constant to the L/DCR ratio. Both methods are validated in the datasheet and supported by the same SENSE+/SENSE− interface with 0–5.5V common-mode range.