Analog Devices Inc. LTC3728LIUH-1#TRPBF

Overview

LTC3728LIUH-1#TRPBF from Analog Devices (formerly Linear Technology) is a dual-channel, 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 OPTI-LOOP® compensation, 0.8 V ±1.5% reference accuracy, and delivers dual regulated outputs (e.g., 5 V/3.3 V @ 5 A each) in notebook power systems and telecom DC distribution.

For engineers reviewing the LTC3728LIUH-1#TRPBF datasheet, LTC3728LIUH-1#TRPBF pinout, LTC3728LIUH-1#TRPBF application, or LTC3728LIUH-1#TRPBF equivalent, key selection considerations include its dual-phase current-mode architecture, absence of overcurrent latchoff, 4.5 V–28 V input range, 5 mm × 5 mm QFN package with exposed pad, and support for Burst Mode®, constant-frequency, and forced-continuous PWM operation.

Technical Context

The LTC3728LIUH-1#TRPBF implements two independent current-mode control loops with 180° phase separation to minimize input ripple and EMI. Each channel uses an error amplifier with transconductance gm = 1.3 mmho and GBW = 3 MHz, referenced to a precision 0.8 V feedback threshold (±1.5% over temperature), and supports soft-start via RUN/SS pins with 0.5–1.2 μA charge current.

Its oscillator offers programmable frequency (260–550 kHz) via PLLIN/PLLFLTR, while FCB pin selection enables three operating modes: Burst Mode® (low-I_Q), constant-frequency discontinuous conduction, or forced continuous PWM. The device lacks overcurrent latchoff-unlike the LTC3728L-but retains foldback current limiting and output overvoltage protection at ±7.5% trip level.

Key Specifications

Pinout & Package

Package: 32-lead (5 mm × 5 mm) plastic QFN (UH) with exposed pad (Pin 33), rated for –40°C to +85°C operation. Exposed pad must be soldered to PCB ground plane for thermal and electrical performance.

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#TRPBF, the LTC3728LIUH-1#TRPBF guarantees full –40°C to +85°C operation and includes enhanced input voltage robustness (35 V abs max for LTC3728LI-1 variants). Versus MP2918GL-Z, it offers superior analog configurability, external clock sync, and embedded 3.3 V bias - at the cost of requiring discrete MOSFETs and external PMBus-free design.

Availability

LTC3728LIUH-1#TRPBF is available at Aetrix Electronics and suitable for notebook power systems, telecom DC distribution, portable instrumentation, and battery-operated digital devices requiring stable component supply, long-term lifecycle support, and guaranteed industrial temperature operation.

Supply support for LTC3728LIUH-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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.

The LTC3728L-1 family was designed by Linear Technology specifically for high-efficiency, dual-phase, N-channel synchronous buck control in space-constrained, thermally demanding applications such as portable computing and telecom infrastructure.

FAQ

What is the maximum input voltage rating for the LTC3728LIUH-1#TRPBF?

The LTC3728LIUH-1#TRPBF has an absolute maximum input voltage (VIN) rating of 30 V. However, the LTC3728LI-1 variant - which shares the same UH package and marking "3728L1" - is rated for up to 35 V input, confirmed in Absolute Maximum Ratings Table 1. Always observe derating guidelines and ensure transient clamping for reliability.

Does the LTC3728LIUH-1#TRPBF support phase synchronization to an external clock?

Yes, the LTC3728LIUH-1#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 filter node and DC frequency tuning input (260–550 kHz range), enabling precise noise-aware frequency placement.

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

The FCB pin on the LTC3728LIUH-1#TRPBF selects among three distinct modes: <0.8 V enables forced continuous PWM; 0.8–2.8 V activates Burst Mode® for high light-load efficiency; >2.8 V disables Burst Mode® for constant-frequency operation. This pin also supports secondary winding regulation - a feature retained from the base LTC3728L-1 design.

What is the purpose of the exposed pad on the LTC3728LIUH-1#TRPBF QFN package?

The exposed pad (Pin 33) on the LTC3728LIUH-1#TRPBF is electrically connected to SGND and serves as the primary thermal path. It must be soldered to a PCB copper pour tied to PGND for optimal thermal performance (θ_JA = 34°C/W) and signal integrity. Leaving it unconnected degrades efficiency, increases junction temperature, and risks instability in high-current operation.

Is overcurrent latchoff enabled in the LTC3728LIUH-1#TRPBF?

No - the LTC3728LIUH-1#TRPBF explicitly lacks overcurrent latchoff. As stated in the product description, it is identical to the LTC3728L except that "the LTC3728L-1 lacks the over current latchoff feature." Instead, it provides foldback current limiting and output overvoltage protection, making it suitable for applications requiring graceful current limiting rather than hard shutdown.