Analog Devices Inc. LTC3446EDE#TRPBF

Overview

LTC3446EDE#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic triple-output DC/DC power management IC integrating a 1A synchronous buck regulator and two 300mA very low dropout (VLDO) linear regulators. It operates from 2.7V–5.5V input, delivers 0.8V buck output and dual 0.4V-referenced VLDO outputs down to 0.4V, and features 2.25MHz switching, ±1.5% reference accuracy, and power-good monitoring. It targets compact Li-ion-powered systems requiring three tightly regulated low-voltage rails.

For engineers reviewing the LTC3446EDE#TRPBF datasheet, LTC3446EDE#TRPBF pinout, LTC3446EDE#TRPBF application, or LTC3446EDE#TRPBF equivalent, key selection considerations include its thermally enhanced 14-pin DFN package, independent enable pins per output, defeatable Burst Mode operation for light-load efficiency, 140µA no-load quiescent current with all outputs enabled, and compatibility with 1µF ceramic capacitors on VLDO outputs.

Technical Context

The LTC3446EDE#TRPBF implements constant-frequency current-mode control in its 2.25MHz synchronous buck stage, using internal P- and N-channel MOSFETs with R_DS(ON) of 130mΩ and 140mΩ respectively. Its error amplifier drives the ITH pin to regulate BUCKFB at 0.800V ±1.5%, enabling precise output setting via external resistive dividers.

Each VLDO regulator uses a 0.400V ±0.5% feedback reference, achieves 70–175mV dropout at 300mA, and remains stable with ≥1µF ceramic output capacitance. The integrated power-good circuit asserts open-drain PGOOD only when all enabled outputs are within ±8% of their target voltages, with LVIN supplied independently from the buck output or an alternate source.

Key Specifications

Pinout & Package

Thermally enhanced 14-pin plastic DFN (4mm × 3mm) with exposed GND pad (Pin 15), rated for –40°C to 125°C junction temperature. Exposed pad must be soldered to PCB ground for electrical integrity and thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar triple-output power management applications.

Compared with TPS65270PWPR and MAX8646ETG+, the LTC3446EDE#TRPBF uniquely combines Li-ion-compatible input range, 2.25MHz switching for miniaturization, defeatable Burst Mode, and true VLDO architecture-making it optimal for portable, battery-critical, and space-limited triple-rail applications.

Availability

LTC3446EDE#TRPBF is available at Aetrix Electronics and suitable for mobile handheld devices, FPGA/CPLD power systems, and low-power IoT sensor nodes requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LTC3446EDE#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 acquired Linear Technology in 2017 and maintains its high-performance analog and power management product lines with rigorous automotive and industrial qualification standards.

The LTC3446EDE#TRPBF belongs to Linear's legacy µPower DC/DC converter family, designed specifically for space- and energy-constrained portable electronics requiring high integration, low quiescent current, and robust multi-rail power delivery.

FAQ

What is the minimum input voltage required for the LTC3446EDE#TRPBF to regulate all three outputs?

The LTC3446EDE#TRPBF requires VIN ≥ LVOUT(MAX) + 1.4V to maintain regulation on both VLDO outputs, per datasheet Note 3. For example, if LVOUT1 = 1.5V and LVOUT2 = 1.2V, VIN must be ≥ 2.9V. Additionally, the buck stage requires VIN ≥ 2.7V. Therefore, the absolute minimum VIN depends on the highest VLDO output voltage configured, not a fixed value across all applications. The LTC3446EDE#TRPBF cannot regulate 1.5V VLDO outputs from a 2.7V input.

Can the LTC3446EDE#TRPBF VLDO regulators operate independently of the buck converter?

Yes, the LTC3446EDE#TRPBF VLDO regulators can operate independently: LVIN may be supplied from any 0.9V–5.5V source (e.g., a separate LDO or battery rail), and ENLDO1/ENLDO2 can be asserted while ENBUCK remains low. The buck stage and VLDO stages have fully independent enable controls and bias paths. The LTC3446EDE#TRPBF datasheet explicitly states "The VLDO regulators may be used independently of the buck converter."

What is the maximum allowable load current on each VLDO output of the LTC3446EDE#TRPBF?

The LTC3446EDE#TRPBF supports up to 300mA continuous output current per VLDO regulator, as specified in the Electrical Characteristics table under "ILVOUT(MAX) Continuous Output Current." Short-circuit current is 760mA, but sustained operation above 300mA risks thermal overload and violates the device's guaranteed specifications. Derating is recommended above 85°C ambient. The LTC3446EDE#TRPBF must be used within this 300mA limit per VLDO to ensure reliability and regulation accuracy.

Does the LTC3446EDE#TRPBF require external compensation components?

Yes, the LTC3446EDE#TRPBF requires external compensation on the ITH pin (Pin 3) for the buck converter's control loop. A series RC network (R_ITH, C_ITH) must be connected from ITH to GND to stabilize the current-mode loop. The VLDO regulators are internally compensated and require no external components beyond their feedback dividers and output capacitors. The LTC3446EDE#TRPBF datasheet provides design equations and typical values in the Applications Information section.

How does the PGOOD pin of the LTC3446EDE#TRPBF behave during startup and fault conditions?

The PGOOD pin of the LTC3446EDE#TRPBF is an open-drain NMOS output that remains low (pulled to GND) until all *enabled* outputs reach and maintain regulation within ±8% of their target voltages for ≥1ms. If any enabled output falls outside this window - due to overcurrent, undervoltage, or thermal shutdown - PGOOD is actively driven low. If no outputs are enabled, PGOOD stays low. The LTC3446EDE#TRPBF does not assert PGOOD until all active rails are verified stable.