Analog Devices Inc. DC1477A

Overview

LTM4609 from Analog Devices (formerly Linear Technology) is a 36V-input, 34V-output buck-boost µModule® regulator integrating controller, power FETs, and support components in a single surface-mount package. It delivers up to 4A continuous output current in boost mode (10A in buck mode), operates from 4.5V to 36V input, supports 0.8V to 34V programmable output voltage via resistor feedback, and achieves up to 98% efficiency in telecom power supplies.

For engineers reviewing the LTM4609 datasheet, LTM4609 pinout, LTM4609 application, or LTM4609 equivalent, this page provides verified technical context, validated pin functions, confirmed operating modes (Burst Mode®, skip-cycle, forced continuous), real-world transient response data, and two rigorously cross-checked alternative buck-boost µModules for high-density point-of-load designs.

Technical Context

The LTM4609 implements a single-inductor, four-switch buck-boost topology with current-mode control, enabling seamless VIN-to-VOUT transitions where input may be above, below, or equal to output. Its internal architecture includes four synchronous MOSFETs (M1–M4) with RDS(ON) values of 10mΩ (M1) and 14–20mΩ (M2–M4), integrated Schottky diodes, and a precision 0.8V feedback reference.

It features phase-lockable fixed-frequency operation (200–400kHz), ultrafast transient response enabled by current-mode stability margins, and dual protection schemes: foldback current limiting triggered by VFB drop and open-drain PGOOD signaling ±7.5% output regulation window violation.

Key Specifications

Pinout & Package

The LTM4609 is available in two RoHS-compliant surface-mount packages: 141-lead LGA (15mm × 15mm × 2.82mm) and 141-lead BGA (15mm × 15mm × 3.42mm), both with SnPb or SAC305 terminal finishes. Pin functions are identical across packages and organized into six banks.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buck-boost µModule applications.

Compared with LTM4609, LTM4618 extends input voltage range at the cost of reduced output current and incompatible pin mapping, while MAXM17504 trades programmability and sync capability for integration and size-making LTM4609 optimal for high-current, EMI-sensitive telecom and industrial systems requiring precise control.

Availability

LTM4609 is available at Aetrix Electronics and suitable for telecom infrastructure, industrial automation, and automotive infotainment systems requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.

Supply support for LTM4609 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 power management semiconductors, acquired Linear Technology in 2017 to expand its µModule portfolio.

The LTM4609 belongs to ADI's µModule regulator family, designed specifically for high-density, high-reliability point-of-load power delivery in space-constrained systems where layout simplicity and thermal performance are critical.

FAQ

What is the maximum output voltage supported by the LTM4609?

The LTM4609 supports an output voltage range of 0.8V to 34V, set by a single external resistor between the VFB and SGND pins. This range is explicitly specified in the Absolute Maximum Ratings and Electrical Characteristics tables, with 34V confirmed as the upper limit for VOUT under all operating conditions including transient events.

Does the LTM4609 require an external inductor, and what value is recommended for 12V output?

Yes, the LTM4609 requires an external inductor. For a 12V output, the datasheet recommends a 5.6µH inductor (as shown in Typical Application TA01a), selected to maintain 20–40% inductor current ripple at full load and switching frequency. Inductor saturation current must exceed peak inductor current, which reaches ~12A in buck mode at 10A output.

How does the LTM4609 handle input voltage variations during cold-crank or load-dump conditions?

The LTM4609 handles cold-crank (down to 4.5V) and load-dump (up to 36V) within its rated input range. Its buck-boost topology automatically transitions between modes: operating in boost when VIN < VOUT (e.g., 6V→12V) and in buck when VIN > VOUT (e.g., 32V→12V), maintaining regulation without interruption or external intervention.

Can the LTM4609 be synchronized to an external clock, and what are the timing requirements?

Yes, the LTM4609 can be synchronized via the PLLIN pin. The external clock must have a frequency between 200kHz and 400kHz, minimum amplitude of 2V, and pulse width ≥400ns. The internal phase-locked loop locks the rising edge of the bottom gate signal to the rising edge of the PLLIN signal, reducing harmonic emissions in noise-sensitive systems.

What protection features are built into the LTM4609, and how do they activate?

The LTM4609 includes overvoltage protection (OVP), foldback current limiting, and PGOOD monitoring. OVP triggers when VFB exceeds ±7.5% of 0.8V, pulling PGOOD low. Foldback current limiting activates when VFB drops below regulation, reducing output current to protect against short circuits. These protections operate autonomously without external circuitry.