Analog Devices Inc. LTC3728LXCUH#TRPBF

Overview

LTC3728LXCUH#TRPBF from Analog Devices (formerly Linear Technology) is a dual-phase, synchronous step-down controller IC driving two independent N-channel MOSFET stages in 180° out-of-phase operation. It delivers up to 5A per channel at 5V/3.3V outputs, supports 4.5V–28V input, features 0.8V ±1% reference accuracy, and operates at phase-lockable frequencies from 250kHz to 550kHz. It is used in high-efficiency notebook DC/DC power rails where input capacitance reduction and low-noise regulation are critical.

For engineers reviewing the LTC3728LXCUH#TRPBF datasheet, LTC3728LXCUH#TRPBF pinout, LTC3728LXCUH#TRPBF application, or LTC3728LXCUH#TRPBF equivalent, key selection criteria include dual-phase current-mode control architecture, OPTI-LOOP™ compensation for wide output capacitor ESR tolerance, integrated 3.3V LDO, PGOOD monitoring with ±7.5% window, and FCB-selectable operating modes (Burst Mode®, constant-frequency, forced continuous).

Technical Context

The LTC3728LXCUH#TRPBF implements a constant-frequency, current-mode control architecture with two independent channels sharing no internal signal coupling except for shared ground and bias references. Each channel uses a transconductance error amplifier (gm = 1.3 mmho, GBW = 3 MHz) driving an ITH-controlled current comparator, with precise 0.8V feedback reference (±1% over temperature) and ±7.5% PGOOD trip threshold.

Its dual-phase 180° interleaving reduces input ripple current by ~70%, minimizing required input capacitance and conducted EMI. The PLLIN/PLLFLTR interface enables external synchronization or DC voltage-based frequency tuning (260–550 kHz), while the FCB pin selects among Burst Mode® (low-I_Q), constant-frequency discontinuous conduction, or forced continuous PWM-each with distinct gate drive timing and reverse-current handling behavior.

Key Specifications

Pinout & Package

Package: 32-lead (5mm × 5mm) plastic QFN with exposed SGND pad (UH package). Thermal resistance θ_JA = 34°C/W. Exposed pad must be soldered to PCB and connected to PGND/SGND.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3728LEUH#TRPBF, the LTC3728LXCUH#TRPBF offers identical functionality at a narrower temperature grade, reducing cost for commercial-grade systems; compared with MP2918GL-Z, it provides superior control flexibility (sync, mode selection, OPTI-LOOP) at the expense of external MOSFET layout complexity.

Availability

LTC3728LXCUH#TRPBF is available at Aetrix Electronics and suitable for notebook computers, telecom DC distribution systems, and portable test instruments requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.

Supply support for LTC3728LXCUH#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 its high-performance power management portfolio with rigorous reliability testing and automotive-grade qualification paths.

The LTC3728L/LTC3728LX product line was designed for high-efficiency, dual-phase DC/DC conversion in space-constrained, thermally demanding applications such as portable computing and telecom infrastructure.

FAQ

What is the operating temperature range for the LTC3728LXCUH#TRPBF?

The LTC3728LXCUH#TRPBF is specified for 0°C to 85°C ambient operation. This commercial-grade temperature range aligns with typical notebook and portable instrument use cases. For extended-temperature applications, consider the LTC3728LEUH#TRPBF (–40°C to 85°C), which shares identical pinout and electrical specifications.

How does the FCB pin affect operating mode selection in the LTC3728LXCUH#TRPBF?

The FCB pin on the LTC3728LXCUH#TRPBF selects among three distinct operating modes: <0.8V enables forced continuous PWM; 0.8V–2.8V activates Burst Mode® for ultra-low I_Q; >4.3V disables Burst Mode® for constant-frequency operation. This pin directly controls gate drive timing, reverse-current handling, and light-load efficiency without requiring external logic.

Can the LTC3728LXCUH#TRPBF synchronize to an external clock source?

Yes, the LTC3728LXCUH#TRPBF supports external synchronization via the PLLIN pin. When driven with a clean square wave, the internal phase-locked loop aligns the rising edge of TG1 to the rising edge of the PLLIN signal. The PLLFLTR pin serves as both phase detector output and DC frequency tuning input (260–550 kHz), enabling precise EMI control.

What protection features does the LTC3728LXCUH#TRPBF provide against overvoltage and short-circuit conditions?

The LTC3728LXCUH#TRPBF includes output overvoltage protection that latches the bottom MOSFET on until VOSENSE returns within ±7.5% of setpoint. It also implements foldback current limiting and programmable short-circuit latchoff using the RUN/SS capacitor time constant - both activated when VOUT drops below 70% of nominal.

Does the LTC3728LXCUH#TRPBF integrate any auxiliary power resources?

Yes, the LTC3728LXCUH#TRPBF integrates a dedicated 3.3V linear regulator (3.3VOUT pin) capable of supplying 10mA DC with 50mA peak current. This eliminates the need for an external LDO to power supervisory circuits, level shifters, or logic interfaces, simplifying system power architecture.