Analog Devices Inc. LTC3870IUFD#PBF

Overview

LTC3870IUFD#PBF from Analog Devices (formerly Linear Technology) is a PolyPhase® step-down slave controller designed for multiphase DC/DC conversion with LTC3880-family master controllers. It delivers precise per-phase current control across two channels, supports 4.5V–60V input, 0.5V–14V output, 100kHz–1MHz synchronization, and operates in CCM or DCM via pin-selectable mode-enabling high-current telecom power supplies.

For engineers reviewing the LTC3870IUFD#PBF datasheet, LTC3870IUFD#PBF pinout, LTC3870IUFD#PBF application, or LTC3870IUFD#PBF equivalent, key selection criteria include phase-shift programmability via PHASMD, dual-channel ITH-based current sharing, EXTVCC support (5V–14V), integrated N-channel gate drivers with <30ns transition times, and guaranteed operation from –40°C to 125°C.

Technical Context

The LTC3870IUFD#PBF implements peak current-mode control with independent ITH0/ITH1 inputs tied directly to master controller outputs, enabling dynamic current sharing without local voltage regulation. Its internal PLL synchronizes switching to an external SYNC clock (100kHz–1MHz) with programmable phase offsets (0°–300°) via PHASMD voltage levels.

Each channel features pin-selectable CCM/DCM operation (MODE0/MODE1), dual-range current limit programming (ILIM pin selecting 45–55mV or 70–80mV sense thresholds), and dedicated fault response (FAULT0/FAULT1 pulling TG/BG low on assertion). Gate drivers deliver 2.5Ω/1.5Ω (TG) and 2.4Ω/1.1Ω (BG) on-resistance with matched 30ns rise/fall times.

Key Specifications

Pinout & Package

28-pin (4mm × 5mm) plastic QFN package with exposed SGND pad (Pin 29) requiring PCB soldering for thermal and signal integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3870IUFD#PBF, LTC3871IUFD#PBF reduces channel count but retains identical thermal and electrical specs per phase, while MP2960AGQSE-LF-Z abandons the digital power management ecosystem entirely-making it unsuitable for upgrades or mixed-master deployments.

Availability

LTC3870IUFD#PBF is available at Aetrix Electronics and suitable for telecom base station power, industrial CPU core supplies, and high-power data center VRMs requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LTC3870IUFD#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 its high-performance power management portfolio with rigorous automotive and industrial qualification standards.

The LTC3870IUFD#PBF belongs to the PolyPhase® digital power system management product line, engineered specifically to extend LTC3880-family master controllers in high-current, multi-phase DC/DC applications demanding precision current sharing and thermal scalability.

FAQ

What is the primary function of the LTC3870IUFD#PBF in a power system?

The LTC3870IUFD#PBF functions exclusively as a PolyPhase® step-down slave controller-it does not regulate output voltage. Instead, it receives ITH voltage commands from a master controller (e.g., LTC3880) to precisely control per-phase peak inductor current, enabling accurate current sharing across multiple phases. The LTC3870IUFD#PBF relies entirely on the master for voltage feedback, fault handling, and sequencing.

How does the PHASMD pin affect timing in the LTC3870IUFD#PBF?

The PHASMD pin on the LTC3870IUFD#PBF sets the phase relationship between the external SYNC clock and the rising edges of TG0/TG1. Applying GND, 1/3 INTVCC, 2/3 INTVCC, or INTVCC yields discrete phase offsets: (180°, 0°), (60°, 300°), (120°, 240°), or (90°, 270°), respectively. This programmability ensures optimal interleaving to minimize input/output capacitor RMS current and EMI peaks in multi-phase systems using the LTC3870IUFD#PBF.

Can the LTC3870IUFD#PBF operate without a master controller?

No-the LTC3870IUFD#PBF cannot operate autonomously. It lacks internal voltage reference, error amplifier, and PWM oscillator independent of SYNC. All critical control signals-including ITH0/ITH1, RUN0/RUN1, FAULT0/FAULT1, and SYNC-must be driven by a compatible master controller (e.g., LTC3880, LTC3883, LTC3886, or LTC3887). Without these connections, the LTC3870IUFD#PBF remains nonfunctional.

What are the consequences of floating the MODE0 and MODE1 pins on the LTC3870IUFD#PBF?

MODE0 and MODE1 each have internal 500kΩ pull-down resistors. If left floating, both pins default to logic low (<1.4V), forcing Channel 0 and Channel 1 into discontinuous conduction mode (DCM). In DCM, the LTC3870IUFD#PBF skips pulses at light loads to improve efficiency but increases output voltage ripple. For forced continuous conduction mode (CCM), actively drive MODE0/MODE1 above 2V (e.g., to INTVCC).

How does EXTVCC improve thermal performance of the LTC3870IUFD#PBF?

When VIN exceeds 6.5V, the LTC3870IUFD#PBF enables an internal LDO that powers INTVCC from EXTVCC (5V–14V) instead of the VIN-derived LDO. This bypasses the high-dropout linear regulator, reducing power dissipation inside the IC by up to 40% in high-input-voltage applications (e.g., 48V telecom rails), thereby lowering junction temperature and improving reliability without changing layout or external components.