Analog Devices Inc. LTC3633AEUFD-1#PBF

Overview

LTC3633AEUFD-1#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. It features current-mode control, selectable 0°/180° phase shift between channels, adjustable switching frequency (500kHz–4MHz), and supports both Burst Mode® and forced continuous operation - enabling high-efficiency power conversion in space-constrained point-of-load applications such as FPGA core supplies and telecom baseband boards.

For engineers reviewing the LTC3633AEUFD-1#PBF datasheet, LTC3633AEUFD-1#PBF pinout, LTC3633AEUFD-1#PBF application, or LTC3633AEUFD-1#PBF equivalent, key selection criteria include its VON sense range (1.5V–12V), dual-channel interleaved operation capability, integrated 3.3V INTVCC and 2.5V V2P5 regulators, and QFN-28 (4mm × 5mm) package with exposed PGND pad for thermal management.

Technical Context

The LTC3633AEUFD-1#PBF implements a controlled on-time, current-mode architecture with an internal phase-locked loop that locks switching frequency to either an internal oscillator (set by RT resistor) or external clock applied to MODE/SYNC. Its two independent buck channels support out-of-phase operation via PHMODE pin to reduce input RMS current and capacitor stress.

Each channel uses internal N-channel MOSFETs (130mΩ top / 65mΩ bottom), senses output voltage via 0.6V reference at VFB pins, and provides programmable soft-start and tracking via TRACKSS pins. The device distinguishes itself from the standard LTC3633A by its extended VON input range (1.5V–12V vs. 0.6V–6V), enabling stable regulation at higher output voltages without external scaling.

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3633AEUFD#PBF, the LTC3633AEUFD-1#PBF enables higher-output-voltage regulation without external scaling, while the MP8859GQ-Z offers higher per-channel current but sacrifices integration, sequencing, and multi-rail coordination capabilities.

Availability

LTC3633AEUFD-1#PBF is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, and portable test equipment requiring stable component supply, extended temperature operation (–40°C to +125°C), and high-density power delivery.

Supply support for LTC3633AEUFD-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 full product support, documentation, and manufacturing continuity for the LTC portfolio.

The LTC3633A family was designed for high-efficiency, dual-channel point-of-load regulation in space-constrained systems requiring precise voltage tracking, low quiescent current, and robust protection - especially in FPGA, ASIC, and DSP power applications.

FAQ

What is the key functional difference between LTC3633AEUFD-1#PBF and LTC3633AEUFD#PBF?

The LTC3633AEUFD-1#PBF features a VON sense range of 1.5V to 12V, whereas the LTC3633AEUFD#PBF supports 0.6V to 6V. This allows the LTC3633AEUFD-1#PBF to directly sense and regulate higher output voltages like 5V or 12V without external resistor dividers, improving accuracy and reducing component count. Both share identical pinout, package, and all other electrical specifications.

Does LTC3633AEUFD-1#PBF support independent enable control for each channel?

Yes. The LTC3633AEUFD-1#PBF provides separate RUN1 (Pin 3) and RUN2 (Pin 6) inputs, each with independent 1.22V turn-on and 1.01V shutdown thresholds. This enables flexible power sequencing - for example, powering up a 3.3V I/O rail before a 1.2V core rail - and dynamic channel disabling to match real-time load demands.

How does the PHMODE pin affect system-level EMI and input capacitor sizing?

When PHMODE is tied to INTVCC, the LTC3633AEUFD-1#PBF operates channels 180° out of phase, interleaving their input current pulses. This reduces RMS input current by up to 30%, allowing smaller input bulk capacitors and lowering conducted EMI. In-phase operation (PHMODE = GND) doubles peak input current, demanding larger CIN and stricter layout for EMI compliance.

Can LTC3633AEUFD-1#PBF regulate two different output voltages simultaneously?

Yes. Each channel has independent feedback (VFB1/VFB2), on-time control (VON1/VON2), and soft-start (TRACKSS1/TRACKSS2) inputs. For example, LTC3633AEUFD-1#PBF can deliver 1.2V/3A on Channel 1 and 5V/3A on Channel 2 using separate resistor dividers and VON connections - with no interaction between regulation loops.

What thermal design considerations apply to LTC3633AEUFD-1#PBF in continuous 3A/channel operation?

The LTC3633AEUFD-1#PBF uses a 4mm × 5mm QFN with exposed PGND pad (Pin 29). To sustain 3A per channel at 125°C junction temperature, the pad must be soldered to ≥4cm² of inner-layer copper with ≥6 thermal vias to internal ground planes. With this layout, θJA remains at 43°C/W, limiting power dissipation to ~1.8W at 85°C ambient.