Analog Devices Inc. LTC3870IUF-1#TRPBF

Overview

LTC3870IUF-1#TRPBF from Analog Devices (formerly Linear Technology) is a PolyPhase® step-down slave controller designed for multiphase DC/DC conversion with digital power system management. It operates as a phase extender paired with the LTC3887-1 master, supports 2-phase to 6-phase configurations, delivers up to 40A per channel, features peak current mode control, and enables accurate inter-chip current sharing across high-current telecom and industrial power supplies.

For engineers reviewing the LTC3870IUF-1#TRPBF datasheet, LTC3870IUF-1#TRPBF pinout, LTC3870IUF-1#TRPBF application, or LTC3870IUF-1#TRPBF equivalent, key selection criteria include its 4.5V–60V input range, 0.5V–14V output voltage support (set by master), 100kHz–1MHz SYNC frequency compatibility, dual-channel PWM outputs with programmable phase shift, and ILIM-selectable 50mV/75mV current sense thresholds.

Technical Context

The LTC3870IUF-1#TRPBF implements a constant-frequency, peak current mode architecture synchronized via falling-edge-triggered SYNC input from an LTC3887-1 master. Its two independent channels (PWM0/PWM1) each feature dedicated ITH-controlled current comparators, MODE0/MODE1-selectable CCM/DCM operation, and PHASMD-programmable relative phase alignment (0°–300° in 60° steps).

It relies entirely on the master controller for voltage regulation and fault management-providing only current regulation per phase. Power is derived from INTVCC (5.0V LDO from VIN or EXTVCC), with EXTVCC support (5V–14V) enabling higher efficiency in high-VIN systems, and all internal logic operates within –40°C to 125°C junction temperature.

Key Specifications

Pinout & Package

Package: 24-lead (4mm × 4mm) plastic QFN (UF), exposed pad (Pin 25) tied to GND and required for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar multiphase slave controller applications.

Compared with LTC3870EUF-1#TRPBF, the LTC3870IUF-1#TRPBF guarantees full –40°C to 125°C operation and is validated for telecom base station thermal profiles; versus ISL68221IRAZ-T7A, it offers direct LTC3887-1 plug-and-play integration, dual-channel symmetry, and hardware-programmable phase/current settings without firmware dependency.

Availability

LTC3870IUF-1#TRPBF is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, and high-performance computing power supplies requiring stable component supply, long-term lifecycle assurance, and guaranteed I-grade temperature performance.

Supply support for LTC3870IUF-1#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 and maintains full product continuity, technical documentation, and manufacturing for the LTC portfolio.

The LTC3870IUF-1#TRPBF belongs to the PolyPhase® digital power system management controller family, engineered specifically to extend phase count and current capacity in high-efficiency, multi-rail DC/DC systems for datacenter, telecom, and industrial applications.

FAQ

What is the primary function of the LTC3870IUF-1#TRPBF in a power system?

The LTC3870IUF-1#TRPBF functions exclusively as a PolyPhase® step-down slave controller-it does not regulate output voltage. Instead, it precisely controls per-phase inductor current under command of a master controller (e.g., LTC3887-1), enabling accurate current sharing, phase synchronization, and scalable high-current delivery in multiphase buck converters. The LTC3870IUF-1#TRPBF relies on the master for voltage feedback, fault management, and configuration.

Can the LTC3870IUF-1#TRPBF operate independently without a master controller like the LTC3887-1?

No-the LTC3870IUF-1#TRPBF cannot operate autonomously. It lacks internal voltage reference, error amplifier, and PWM oscillator autonomy. All critical control signals-including ITH (current threshold), RUN (enable), SYNC (clock), and FAULT (protection)-must be driven by a compatible master such as the LTC3887-1. Without those inputs, the LTC3870IUF-1#TRPBF remains nonfunctional; its design assumes tightly coupled digital power system management.

How does the ILIM pin affect current sensing on the LTC3870IUF-1#TRPBF?

The ILIM pin on the LTC3870IUF-1#TRPBF selects the full-scale current sense threshold for both channels: GND sets 50mV (low range), INTVCC sets 75mV (high range), and resistor dividers enable asymmetric configurations (e.g., Channel 0 high / Channel 1 low). This setting must match the MFR_PWM_MODE_3887-1 register bit 7 in the master controller to ensure consistent overcurrent protection and current sharing across all phases in the LTC3870IUF-1#TRPBF-based system.

What is the role of the PHASMD pin, and what phase offsets does it support?

The PHASMD pin on the LTC3870IUF-1#TRPBF programs the relative phase relationship between the SYNC clock and each PWM output. With four valid states-GND, 1/3 INTVCC, 2/3 INTVCC (or float), and INTVCC-it configures PWM0/PWM1 phase offsets of (180°/0°), (60°/300°), (120°/240°), or (90°/270°), respectively. This enables optimal interleaving across 2-, 3-, 4-, or 6-phase topologies to minimize input/output ripple and EMI in the LTC3870IUF-1#TRPBF implementation.

Does the LTC3870IUF-1#TRPBF support both DCR and resistor-based current sensing?

Yes-the LTC3870IUF-1#TRPBF supports both inductor DCR sensing (via ISENSE0±/ISENSE1± differential inputs) and discrete RSENSE shunt sensing. DCR sensing eliminates power loss but requires compensation for copper tolerance; RSENSE provides higher accuracy at the cost of added I²R loss. For matched current sharing, the sensing method and component values must be identical between all master and slave controllers in the LTC3870IUF-1#TRPBF system.