Analog Devices Inc. LTM4609IY

Overview

LTM4609IY from Analog Devices (formerly Linear Technology) is a 141-lead BGA µModule® buck-boost DC/DC regulator delivering up to 4A continuous output current in boost mode (10A in buck mode), with 4.5V–36V input and 0.8V–34V programmable output voltage, housed in a RoHS-compliant 15mm × 15mm × 3.42mm BGA package. It enables high-density point-of-load regulation in telecom power supplies where VIN may exceed, fall below, or equal VOUT.

For engineers reviewing the LTM4609IY datasheet, LTM4609IY pinout, LTM4609IY application, or LTM4609IY equivalent, this page delivers verified technical context, validated pin functions, confirmed operating modes (Burst, skip-cycle, forced continuous), real-world efficiency curves (up to 98%), and precise thermal derating guidance for industrial and networking equipment design.

Technical Context

The LTM4609IY integrates a current-mode buck-boost controller, four synchronous power MOSFETs (M1–M4), gate drivers, internal compensation, and protection circuitry in a single module. Its single-inductor architecture supports seamless transition between buck and boost operation without external mode control logic.

It features phase-lockable fixed-frequency operation (200–400 kHz), programmable via PLLFLTR voltage or external clock on PLLIN, with ultrafast transient response enabled by current-mode control and low R_DS(ON) switches (M1: 10 mΩ typ, M2–M4: 14–20 mΩ). Fault protection includes foldback current limiting, output overvoltage detection (±7.5% window), and PGOOD open-drain status signaling.

Key Specifications

Pinout & Package

Package: 141-ball BGA, 15mm × 15mm × 3.42mm, RoHS-compliant SAC305 solder finish (e1), MSL Level 3.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTM4609IY, LTM4608IY offers identical form factor and interface but reduced current capacity, while LTM4622IY provides dual independent buck outputs at smaller size but cannot regulate VOUT > VIN - making LTM4609IY uniquely suited for wide-input, high-VOUT, single-rail buck-boost applications.

Availability

LTM4609IY 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 BGA packaging.

Supply support for LTM4609IY 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 µModule® product line as high-integration power solutions combining ICs, power devices, and passives in compact packages.

The LTM4609IY belongs to the µModule buck-boost regulator family designed for space-constrained, high-reliability applications needing wide input/output voltage flexibility without discrete power stage design effort.

FAQ

What is the maximum output voltage supported by the LTM4609IY?

The LTM4609IY supports an output voltage range of 0.8V to 34V, set by a single external resistor connected between the VFB pin and SGND. This wide range allows it to generate high-voltage rails such as 24V, 30V, or 34V directly from lower input sources - critical for applications like analog front-ends, industrial sensors, and telecom bias supplies. The 34V upper limit is absolute and validated across temperature and load conditions per the datasheet.

Does the LTM4609IY support external frequency synchronization?

Yes, the LTM4609IY supports external frequency synchronization via the PLLIN pin (Pin B9), which accepts a 200–400 kHz square wave clock signal with ≥2V amplitude and ≥400 ns pulse width. When enabled, the internal phase-locked loop aligns the rising edge of the bottom-gate switch to the external clock's rising edge - essential for reducing beat frequencies and EMI in multi-module systems. The LTM4609IY must be powered and running before synchronization engages.

How does the FCB pin control operating modes in the LTM4609IY?

The FCB pin (Pin A9) selects among three distinct operating modes: (1) <0.8V → forced continuous conduction mode in both buck and boost; (2) 0.85–5.3V → Burst Mode® in boost / skip-cycle in buck for light-load efficiency; (3) >5.3V → constant-frequency discontinuous conduction mode. These modes are internally decoded and applied without external logic, allowing simple resistor-divider or GPIO-based control of LTM4609IY behavior across load conditions.

What thermal performance can be expected from the LTM4609IY in a standard 4-layer PCB?

In a standard 4-layer PCB with 2 oz copper, 10 cm² exposed thermal pad area, and no forced airflow, the LTM4609IY achieves θ_JA = 11.4°C/W and θ_JCbottom = 4°C/W. At 4A boost load (32V_IN/12V_OUT), typical power dissipation is ~1.8W, resulting in ~20°C junction-to-ambient rise - well within the 125°C T_JMAX limit. Derating begins above 85°C ambient, per the published output current derating curves in the datasheet.

Is the LTM4609IY pin-compatible with other LTM46xx µModule regulators?

No, the LTM4609IY is not pin-compatible with other LTM46xx devices. While it shares the 15mm × 15mm BGA footprint with LTM4608IY, its pin assignment differs significantly - particularly for SW1/SW2 placement, RSENSE location, and PLLIN/PLLFLTR functionality. Substituting without layout revision will cause functional failure. Always verify pin mapping using the official LTM4609IY datasheet's Table 6 and mechanical drawings before board reuse.