Analog Devices Inc. LTC3728LIUH-1#PBF

Overview

LTC3728LIUH-1#PBF from Analog Devices (formerly Linear Technology) is a dual-phase, 180° out-of-phase, synchronous step-down controller driving all-N-channel MOSFET stages for high-efficiency DC/DC conversion. It operates at a phase-lockable fixed frequency up to 550 kHz, features ±1.5% output voltage accuracy, 0.8 V reference, and power-good indication. It targets high-current, low-noise dual-rail supplies in notebook computers and telecom systems.

For engineers reviewing the LTC3728LIUH-1#PBF datasheet, LTC3728LIUH-1#PBF pinout, LTC3728LIUH-1#PBF application, or LTC3728LIUH-1#PBF equivalent, key selection criteria include dual-phase interleaving for input ripple reduction, OPTI-LOOP® compensation for wide output capacitance tolerance, absence of overcurrent latchoff, and support for Burst Mode®, constant-frequency, and forced continuous PWM operation.

Technical Context

The LTC3728LIUH-1#PBF implements two independent current-mode control loops with 180° phase offset, minimizing RMS input current and EMI. Its constant-frequency architecture supports PLL synchronization via PLLIN and frequency tuning via PLLFLTR (260–550 kHz range), while OPTI-LOOP® compensation adapts loop response to varying COUT and ESR.

It integrates dual gate drivers (TG/BG) with fast transitions (≤100 ns), a precision 0.8 V feedback reference, a dedicated 3.3 V LDO (10 mA), and a power-good output asserting when both VOSENSE pins deviate >±7.5% from setpoint. The FCB pin selects operating mode-Burst Mode®, constant-frequency, or forced continuous-without requiring external logic.

Key Specifications

Pinout & Package

Package: 32-lead (5 mm × 5 mm) plastic QFN with exposed pad (pin 33 = GND). Thermal resistance θJA = 34°C/W; requires soldering of exposed pad 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 LTC3728LEUH-1#PBF and LTC3728LIGN-1#PBF, the LTC3728LIUH-1#PBF offers guaranteed operation down to –40°C and superior thermal performance (θJA = 34°C/W), making it the sole choice for ruggedized portable or outdoor-deployed equipment requiring full industrial temperature compliance and compact layout.

Availability

LTC3728LIUH-1#PBF is available at Aetrix Electronics and suitable for notebook computers, telecom intermediate bus converters, and portable instrumentation requiring stable component supply with guaranteed industrial temperature range and QFN thermal performance.

Supply support for LTC3728LIUH-1#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 qualification and long-term product support.

The LTC3728L family delivers dual-phase synchronous buck control for high-density, low-EMI DC/DC conversion in space-constrained portable and telecom applications, emphasizing thermal efficiency, input ripple reduction, and flexible operating mode selection.

FAQ

What is the key functional difference between LTC3728LIUH-1#PBF and LTC3728L-1?

The LTC3728LIUH-1#PBF is the industrial-grade variant of the LTC3728L-1 family, specified for operation from –40°C to +85°C and packaged in a 32-lead QFN. It lacks the overcurrent latchoff feature present in non-"L" versions (e.g., LTC3728-1), enabling automatic recovery after short-circuit faults. All electrical specifications-including 400 kHz nominal frequency, 0.8 V reference, and dual-phase interleaving-are identical to the base LTC3728L-1 design.

Does LTC3728LIUH-1#PBF support synchronization to an external clock?

Yes, LTC3728LIUH-1#PBF supports full phase synchronization via its PLLIN pin, which accepts an external TTL/CMOS clock signal. The internal phase-locked loop aligns the rising edge of TG1 to the rising edge of the PLLIN signal. Simultaneously, the PLLFLTR pin allows DC voltage tuning of the oscillator frequency from 260 kHz to 550 kHz, enabling precise frequency matching across multiple LTC3728LIUH-1#PBF units in a system.

How does the FCB pin affect operating mode selection in LTC3728LIUH-1#PBF?

The FCB pin on LTC3728LIUH-1#PBF selects among three distinct operating modes: pulling FCB below 0.8 V forces continuous PWM operation; leaving FCB open enables Burst Mode® for highest light-load efficiency; tying FCB to INTVCC (>4.3 V) disables Burst Mode® and enforces constant-frequency discontinuous conduction. This single-pin control eliminates external mode-selection logic and simplifies firmware integration.

What is the purpose of the 3.3VOUT pin on LTC3728LIUH-1#PBF?

The 3.3VOUT pin on LTC3728LIUH-1#PBF is an integrated linear regulator delivering up to 10 mA at 3.3 V ±5%, with <2% load regulation. It is designed to power auxiliary circuitry such as level shifters, monitoring ICs, or small logic blocks-reducing bill-of-materials count and eliminating the need for a separate 3.3 V supply. It remains active during normal operation but shuts down when both RUN/SS pins are pulled low.

Can LTC3728LIUH-1#PBF be used in single-channel configurations?

Yes, LTC3728LIUH-1#PBF supports independent operation of each channel: RUN/SS1 and RUN/SS2 can be controlled separately to enable or disable individual controllers, and VOSENSE1/SENSE1+/– and VOSENSE2/SENSE2+/– are fully isolated. This allows use as two discrete synchronous buck controllers on one die-ideal for asymmetric rail generation (e.g., 5 V @ 5 A + 3.3 V @ 3 A) without cross-talk or shared timing constraints.