Analog Devices Inc. LTC3633AIFE-1#PBF

Overview

LTC3633AIFE-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° interchannel phase shift, adjustable 500kHz–4MHz switching frequency, and supports both Burst Mode® and forced continuous operation. It is used in high-density point-of-load power supplies for FPGA, ASIC, and DSP core voltage regulation.

For engineers reviewing the LTC3633AIFE-1#PBF datasheet, LTC3633AIFE-1#PBF pinout, LTC3633AIFE-1#PBF application, or LTC3633AIFE-1#PBF equivalent, key selection considerations include its 1.5V–12V VON sense range (distinguishing it from the LTC3633A), TSSOP-28 package with exposed PGND pad, dual-channel interleaved operation for reduced input ripple, and integrated overvoltage/overtemperature protection.

Technical Context

The LTC3633AIFE-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 INTVCC default) or external clock applied to MODE/SYNC. Its dual channels operate independently with separate RUN, FB, TRACKSS, ITH, and VON inputs, enabling asymmetric output configurations.

It integrates two high-efficiency synchronous buck stages with top/bottom MOSFETs (R_DS(ON) = 130mΩ/65mΩ), 0.6V reference (±1% over temp), and dedicated PGOOD outputs per channel. The LTC3633A-1 variant specifically supports 1.5V–12V output sensing via VON pins-critical for higher-voltage rails-while maintaining pin compatibility with the base LTC3633A in TSSOP-28.

Key Specifications

Pinout & Package

Package: 28-Lead Plastic TSSOP with exposed PGND pad (Pin 29), rated for –40°C to +125°C junction temperature (θ_JA = 30°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 MPQ4433AGL-A-Z, the LTC3633AIFE-1#PBF delivers true dual-channel integration with phase control and rail-specific sequencing, while compared with LTC3633AEFE#PBF, it enables accurate 1.5V–12V output regulation without external feedback scaling - critical for high-precision, high-voltage point-of-load designs.

Availability

LTC3633AIFE-1#PBF is available at Aetrix Electronics and suitable for industrial PLCs, test equipment, networking edge devices, and medical handhelds requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant manufacturing.

Supply support for LTC3633AIFE-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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LTC3633A family was designed for high-efficiency, space-constrained point-of-load regulation in FPGA, ASIC, and DSP applications - emphasizing dual-rail flexibility, thermal robustness, and seamless integration with complex power sequencing requirements.

FAQ

What is the key functional difference between LTC3633AIFE-1#PBF and LTC3633AEFE#PBF?

The LTC3633AIFE-1#PBF supports a 1.5V–12V VON sense range, enabling direct feedback from higher-voltage outputs like 5V or 12V without external resistor dividers. In contrast, the LTC3633AEFE#PBF has a 0.6V–6V VON range and cannot natively regulate above 6V using VON feedback. This makes LTC3633AIFE-1#PBF essential for dual-rail systems where one output exceeds 6V, preserving accuracy and simplifying layout. Both share identical pinout, package, and thermal specs.

Does LTC3633AIFE-1#PBF support external frequency synchronization, and how is it implemented?

Yes, LTC3633AIFE-1#PBF supports external frequency synchronization via the MODE/SYNC pin. When a clean CMOS/TTL clock signal is applied, an internal phase-locked loop locks the bottom NMOS turn-on edge to the rising edge of the input clock, ensuring jitter-free operation. Synchronization forces forced continuous mode and overrides Burst Mode. The supported frequency range matches the internal programmable range (500kHz–4MHz), and no additional components are required beyond proper AC coupling and termination.

How does the 180° phase shift feature in LTC3633AIFE-1#PBF reduce input capacitance requirements?

By configuring LTC3633AIFE-1#PBF for 180° out-of-phase operation (via PHMODE = INTVCC), the input current pulses from each channel are interleaved. This reduces peak-to-peak and RMS input current by up to 30% compared to in-phase operation, directly lowering the required input bulk capacitance. For example, a design using two 10µF X7R ceramics in parallel may achieve equivalent ripple suppression with a single 10µF capacitor - saving board space and cost while improving supply rail stability.

Can LTC3633AIFE-1#PBF safely power a 12V output rail, and what design considerations apply?

Yes, LTC3633AIFE-1#PBF can safely regulate a 12V output using its 1.5V–12V VON sense range - tie VON2 directly to VOUT2 to enable proportional on-time control. Critical considerations include verifying minimum on-time (20ns) suffices at 12V_OUT/20V_IN (duty ≈ 60%), selecting an inductor with adequate saturation current (>3.5A), and ensuring thermal design accommodates ~1.5W dissipation at full load. Input overvoltage protection (22.5V trip) remains active on VIN2.

What is the role of the TRACKSS pins in LTC3633AIFE-1#PBF, and how do they differ from standard soft-start?

The TRACKSS1 and TRACKSS2 pins in LTC3633AIFE-1#PBF provide combined tracking and soft-start functionality. Applying a voltage <0.6V (e.g., from another regulator's output) causes LTC3633AIFE-1#PBF to servo its VFB pin to match that voltage - enabling precise power-rail sequencing. With no external voltage, the internal 1.4µA pull-up current charges an external capacitor to SGND, generating a linear soft-start ramp. This dual capability eliminates need for external tracking ICs or discrete RC timers in multi-rail systems.