Analog Devices Inc. LTC1871XMS#PBF

Overview

LTC1871XMS#PBF from Analog Devices (formerly Linear Technology) is a wide-input-range, current-mode DC/DC controller IC for boost, flyback, and SEPIC topologies, driving an external N-channel MOSFET. It operates from 2.5V to 36V input, delivers up to 92% duty cycle, supports programmable switching frequency from 65kHz to 900kHz, and is fully rated for 175°C junction temperature-enabling use in high-reliability industrial and automotive power supplies.

For engineers reviewing the LTC1871XMS#PBF datasheet, LTC1871XMS#PBF pinout, LTC1871XMS#PBF application, or LTC1871XMS#PBF equivalent, key selection criteria include its No RSENSE™ current sensing capability, Burst Mode® operation for ultra-low-light-load efficiency, ±2% FB reference accuracy over temperature, internal 5.2V LDO, and robust 10-lead MSOP package with 120°C/W thermal resistance.

Technical Context

The LTC1871XMS#PBF implements peak current-mode control with internal slope compensation, enabling stable operation up to 92% duty cycle without external compensation. Its current sense architecture leverages the MOSFET's R_DS(ON) (No RSENSE™), reducing component count and conduction losses-while retaining compatibility with external shunt resistors for high-output-voltage applications (>36V).

It features dual-mode operation: Burst Mode® (enabled via MODE/SYNC = GND or open) for <10μA quiescent current at no load, and continuous/pulse-skip mode (MODE/SYNC ≥2V) for fixed-frequency, low-ripple performance. The RUN pin provides precise 1.248V turn-on threshold with 100mV hysteresis, and the FREQ pin sets oscillator frequency with a single resistor.

Key Specifications

Pinout & Package

Package: 10-lead plastic MSOP (MS package), 3mm × 3mm body, 0.5mm pitch, exposed pad not specified for LTC1871XMS#PBF per ordering info. Thermal resistance θ_JA = 120°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar boost/flyback/SEPIC controller applications.

Compared with LT3757AEMSE#PBF and TPS40210DRCT, the LTC1871XMS#PBF uniquely combines No RSENSE™ sensing, 175°C operation, and 2.5V minimum input-making it the only choice for ultra-efficient, high-reliability boost/flyback in thermally aggressive, battery-fed systems.

Availability

LTC1871XMS#PBF is available at Aetrix Electronics and suitable for telecom power supplies, portable electronic equipment, industrial sensor transmitters, and automotive body control modules requiring stable component supply across extended temperature and long product lifecycles.

Supply support for LTC1871XMS#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 acquired Linear Technology in 2017 and maintains full support for legacy Linear power products. Linear Technology pioneered high-performance analog ICs with emphasis on precision, ruggedness, and thermal reliability.

The LTC1871XMS#PBF belongs to Linear's high-temperature controller family, designed specifically for demanding power conversion in automotive, industrial, and aerospace applications where extended temperature operation and minimal external components are essential.

FAQ

What is the maximum input voltage the LTC1871XMS#PBF can handle?

The LTC1871XMS#PBF has an absolute maximum VIN rating of 36V and is specified to operate continuously from 2.5V to 36V. Exceeding 36V may cause permanent damage. For applications with transient overvoltages (e.g., automotive load dump), external clamping or filtering is required before the VIN pin. The SENSE pin also shares the same 36V absolute max rating, so high-voltage flyback configurations require careful layout and voltage division.

Does the LTC1871XMS#PBF support synchronization to an external clock?

Yes, the LTC1871XMS#PBF supports synchronization via the MODE/SYNC pin. When driven with a clean logic-level clock (≥2V pulse width ≥25ns, ≤80% duty cycle), the internal oscillator locks to frequencies up to 1.3× its nominal f_OSC. Synchronization disables Burst Mode® and increases internal slope compensation by ~30%, which helps prevent subharmonic oscillation above 50% duty cycle.

How does the No RSENSE™ feature work in the LTC1871XMS#PBF?

The LTC1871XMS#PBF senses current by measuring the voltage drop across the power MOSFET's R_DS(ON) via the SENSE pin connected to the MOSFET drain. This eliminates the power loss and board space of an external sense resistor. The controller uses internal leading-edge blanking to reject switching noise and has a typical current sense threshold of 150mV, corresponding to peak current I_PEAK = 0.15V / R_DS(ON).

Can the LTC1871XMS#PBF be used in flyback topology with primary-side regulation?

Yes, the LTC1871XMS#PBF supports flyback operation using primary-side sensing. Connect the SENSE pin to the MOSFET drain and the FB pin to an auxiliary winding-based voltage divider. The controller regulates based on reflected output voltage, eliminating the need for optocouplers or secondary-side references-ideal for cost- and space-constrained isolated supplies.

What thermal considerations apply to the LTC1871XMS#PBF in a 10-lead MSOP package?

The LTC1871XMS#PBF in the 10-lead MSOP has θ_JA = 120°C/W. To maintain T_J ≤175°C, calculate power dissipation as P_IC = V_IN × (I_Q + f_OSC × Q_G). At high VIN and high f_OSC, gate charge current dominates. Ensure adequate copper area under the package (even without exposed pad) and consider airflow or heatsinking for sustained >100mA average output current applications.