Analog Devices Inc. LTC3633AEUFD-3#PBF

Overview

LTC3633AEUFD-3#PBF from Analog Devices (formerly Linear Technology) is a dual-channel monolithic synchronous step-down regulator delivering 3A per channel across a 3.6V–20V input range, featuring selectable 0°/180° phase shift, adjustable 500kHz–4MHz switching frequency, and 0.6V reference for low-output-voltage regulation in point-of-load power supplies.

For engineers reviewing the LTC3633AEUFD-3#PBF datasheet, LTC3633AEUFD-3#PBF pinout, LTC3633AEUFD-3#PBF application, or LTC3633AEUFD-3#PBF equivalent, key selection criteria include its 1.5V–12V VON sense range (distinguishing it from LTC3633A-2), dual-channel out-of-phase operation capability, Burst Mode® vs forced continuous mode control, and QFN-28 (4mm × 5mm) thermal performance with exposed PGND pad.

Technical Context

The LTC3633AEUFD-3#PBF employs a controlled on-time, current-mode architecture with internal PLL synchronization to maintain constant frequency across load and line variations. Its dual channels support independent enable (RUN1/RUN2), phase-selectable operation (PHMODE), and external frequency programming via RT resistor or MODE/SYNC clock input.

Each channel integrates high-side and low-side MOSFETs with 130mΩ/65mΩ R_DS(ON), supports output voltage tracking and soft-start via TRACKSS pins, and provides independent PGOOD status outputs with ±8% fault detection and 40µs filtering. Input overvoltage lockout triggers at 22.5V and recovers at 21.5V.

Key Specifications

Pinout & Package

Package: 28-lead (4mm × 5mm) plastic QFN with exposed PGND pad (Pin 29), rated for –40°C to 125°C junction temperature, θ_JA = 43°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3633AEUFD-2#PBF, the LTC3633AEUFD-3#PBF supports higher output voltages with improved VON-based frequency accuracy above 1.5V, while compared with TPS543B20RTWR, it delivers dual-rail integration in one QFN-28 package without PMBus overhead or secondary IC cost.

Availability

LTC3633AEUFD-3#PBF is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive ADAS camera ECUs, and test & measurement FPGA core power supplies requiring stable component supply, extended temperature operation, and dual-rail POL integration.

Supply support for LTC3633AEUFD-3#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 LTC3633A product line delivers dual-channel monolithic synchronous buck regulators optimized for space-constrained, high-efficiency point-of-load applications demanding precise voltage tracking, low quiescent current, and robust protection.

FAQ

What is the VON sense range for LTC3633AEUFD-3#PBF, and why does it matter?

The LTC3633AEUFD-3#PBF has a VON sense range of 1.5V to 12V, which defines the valid output voltage window where on-time remains proportional to VOUT for accurate frequency regulation. Using this part outside that range-such as for 1.0V outputs-causes switching frequency deviation and potential instability. This distinguishes it from the LTC3633A-2 variant and ensures optimal performance in mid-to-high voltage POL applications.

How does the PHMODE pin affect system-level EMI in LTC3633AEUFD-3#PBF designs?

When PHMODE is tied to INTVCC, LTC3633AEUFD-3#PBF operates its two channels 180° out of phase, causing input current ripple components to cancel partially. This reduces peak-to-peak input capacitor ripple current by up to 70%, lowering conducted EMI and allowing smaller input bulk capacitance. In contrast, in-phase operation (PHMODE = GND) doubles input ripple amplitude and increases EMI filter requirements.

Can LTC3633AEUFD-3#PBF be synchronized to an external clock, and what happens to its operating mode?

Yes, LTC3633AEUFD-3#PBF can be synchronized by applying a clean clock signal to the MODE/SYNC pin. When driven externally, the internal PLL locks to the rising edge of that clock, and the device automatically enters forced continuous conduction mode-even if MODE/SYNC was previously configured for Burst Mode®. This ensures deterministic timing for noise-sensitive systems like ADC power supplies.

What thermal design considerations apply to the exposed pad of LTC3633AEUFD-3#PBF?

The exposed PGND pad (Pin 29) of LTC3633AEUFD-3#PBF must be soldered to a thermally robust PCB copper area with ≥6 thermal vias to internal ground planes. With θ_JA = 43°C/W, inadequate pad soldering raises junction temperature beyond 125°C under 3A/channel load, triggering overtemperature shutdown. Recommended layout uses 10mm² minimum copper area and solder mask defined pads to ensure reliable thermal transfer.

Does LTC3633AEUFD-3#PBF support output voltage tracking, and how is it implemented?

Yes, LTC3633AEUFD-3#PBF supports independent output voltage tracking via TRACKSS1 and TRACKSS2 pins. Applying a ramp voltage (e.g., from another regulator's soft-start output) to TRACKSSx causes the corresponding channel's FB pin to servo to that voltage until it exceeds 0.6V, enabling precise power sequencing. An internal 1.4µA pull-up current allows simple soft-start implementation with a single capacitor to SGND per channel.