Analog Devices Inc. LTC3875IUJ#PBF

Overview

LTC3875IUJ#PBF from Analog Devices (formerly Linear Technology) is a dual-output, 2-phase synchronous step-down DC/DC controller driving all-N-channel MOSFET stages. It delivers precise 0.6V ±0.5% output voltage accuracy, supports 4.5V–38V input, enables low-DCR current sensing down to 10mV threshold, and features DCR temperature compensation and thermal balancing for multichip 60A server power rails.

For engineers reviewing the LTC3875IUJ#PBF datasheet, LTC3875IUJ#PBF pinout, LTC3875IUJ#PBF application, or LTC3875IUJ#PBF equivalent, key selection criteria include dual-phase interleaving for reduced input ripple, programmable 250kHz–720kHz switching frequency, remote differential sensing for <1% load regulation, and thermal-balanced current sharing across parallel controllers in high-density telecom and data center power systems.

Technical Context

The LTC3875IUJ#PBF implements dual independent current-mode control loops with per-phase ITH-based peak current limiting and 0.6V reference servo loop. Its architecture integrates two high-speed remote-sense differential amplifiers (VOSNS±), programmable DCR temperature compensation via TCOMP pins, and thermal averaging through TAVG for multi-IC current balancing.

It supports phase-lockable operation up to 12-phase via CLKOUT/PHASMD/MODE-PLLIN, employs fast transient enhancement on Channel 2 via IFAST, and provides foldback current limiting, short-circuit soft recovery, and ±7.5% output overvoltage protection with PGOOD monitoring - all within a single 40-lead 6mm × 6mm QFN package.

Key Specifications

Pinout & Package

Package: 40-lead plastic QFN (6mm × 6mm, 0.5mm pitch), exposed thermal pad (Pin 41 = SGND/PGND) requiring solder connection to PCB ground plane for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3873EUJ#PBF and MP2960AGQSE-Z, the LTC3875IUJ#PBF uniquely combines dual independent outputs, DCR temperature compensation, and thermal balancing - making it the only option capable of delivering stable 60A+ output with <0.5% accuracy and coordinated thermal management across multiple ICs in mission-critical infrastructure.

Availability

LTC3875IUJ#PBF is available at Aetrix Electronics and suitable for server VR13/VR14 core power, telecom 48V intermediate bus conversion, and industrial PLC I/O power supplies requiring stable component supply, long-term lifecycle support, and guaranteed –40°C to 125°C operation.

Supply support for LTC3875IUJ#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 product support, documentation, and manufacturing continuity for the LTC portfolio.

The LTC3875 belongs to Linear's high-performance power controller family, designed specifically for high-current, multi-phase, thermally demanding applications in data centers, telecom infrastructure, and industrial automation where precision, efficiency, and reliability are non-negotiable.

FAQ

What is the maximum supported switching frequency for the LTC3875IUJ#PBF?

The LTC3875IUJ#PBF supports a programmable switching frequency range from 250kHz to 720kHz. This is set via the FREQ pin, which sinks a precise 10µA current; connecting a resistor to ground generates a voltage that determines the oscillator frequency. At VFREQ = 2.4V or higher, the device operates at its maximum nominal frequency of 720kHz, enabling compact magnetics in high-density power designs.

Does the LTC3875IUJ#PBF support remote voltage sensing, and how is it implemented?

Yes, the LTC3875IUJ#PBF supports true dual remote sensing via dedicated differential amplifier inputs: VOSNS1+/VOSNS1– for Channel 1 and VOSNS2+/VOSNS2– for Channel 2. These pins connect directly to the output voltage divider and capacitor terminals, respectively, forming a Kelvin sense path that rejects PCB trace resistance errors. This architecture achieves <0.1% load regulation and is essential for maintaining accuracy in high-current, distributed-point-of-load systems.

How does the thermal balancing function work in the LTC3875IUJ#PBF?

The LTC3875IUJ#PBF implements thermal balancing by measuring channel temperature via external NTC thermistors connected to TCOMP1/TCOMP2, converting those signals to currents mirrored to TRSET1/TRSET2, then summing them at the TAVG node. When ENTMPB is grounded, the controller dynamically adjusts per-phase ITH thresholds to equalize average die temperature across multiple LTC3875ICs - critical for reliability in 12-phase stacks powering AI accelerators or high-end FPGAs.

Can the LTC3875IUJ#PBF operate with very low-DCR inductors, and what is the minimum sense threshold?

Yes, the LTC3875IUJ#PBF is specifically optimized for low-DCR inductor sensing, supporting programmable current sense thresholds from 10mV to 30mV. This is achieved using combined AC/DC sensing (SNSA+/SNSD+/SNS– pins) with internal gain of 5× for AC ripple, allowing accurate current measurement even with inductors as low as 0.32mΩ - eliminating power loss and board space consumed by discrete sense resistors in >40A applications.

What are the key differences between the UJ and UH package variants of the LTC3875?

The LTC3875IUJ#PBF uses a 40-lead 6mm × 6mm QFN (0.5mm pitch) with θJA = 33°C/W and θJC = 2.0°C/W, while the UH variant is a 5mm × 5mm QFN (0.4mm pitch) with θJA = 44°C/W and θJC = 7.3°C/W. The UJ package offers superior thermal performance for high-power, continuous-duty applications like server VRMs, whereas the UH variant prioritizes board area reduction in space-constrained telecom modules - both share identical pinout and electrical functionality.