Analog Devices Inc. DC2481A-B

Overview

LTM4650 from Analog Devices is a dual-output 25A µModule DC/DC regulator (or single 50A output) operating from 4.5V–15V input, delivering 0.6V–1.8V per channel with ±1.5% total DC output error, differential remote sensing, and current-mode control for fast transient response in FPGA/ASIC core power applications.

For engineers reviewing the LTM4650 datasheet, LTM4650 pinout, LTM4650 application, or LTM4650 equivalent, key selection considerations include its 16mm × 16mm BGA package, dual-channel current sharing up to 300A in multiphase configurations, programmable switching frequency (400–780 kHz), and integrated temperature monitoring via TEMP pin.

Technical Context

The LTM4650 integrates two independent current-mode buck regulators with internal MOSFETs, inductors, and compensation-enabling stable operation with all-ceramic output capacitors. Its 90ns minimum on-time and 400–780kHz adjustable switching frequency support high-efficiency regulation across wide VIN/VOUT ratios.

Dual-channel operation supports independent voltage tracking, soft-start sequencing, and multiphase parallelization via MODE_PLLIN, PHASMD, and CLKOUT pins. Fault protection includes overvoltage lockout (0.64–0.68V at VFB), overcurrent foldback, and open-drain PGOOD outputs asserting within ±10% of regulation.

Key Specifications

Pinout & Package

144-ball BGA package (16mm × 16mm × 5.01mm), RoHS-compliant SAC305 finish, MSL Level 3, rated for –40°C to 125°C (E/I grade) or –55°C to 125°C (MP grade).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-output high-current DC/DC regulator applications.

Compared with LTM4650, LTM4630-1 offers identical mechanical fit but reduced current capacity and higher light-load efficiency, while TPS546D24A trades integration for digital configurability and telemetry-making it suitable for datacenter power architectures requiring runtime adaptation.

Availability

LTM4650 is available at Aetrix Electronics and suitable for telecom baseband processing, industrial FPGA systems, and storage controller power applications requiring stable component supply across extended temperature grades and long production lifecycles.

Supply support for LTM4650 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 is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, communications, and industrial markets since 1965.

The LTM4650 belongs to the µModule regulator product line-designed to deliver complete, verified, high-current DC/DC solutions in compact BGA packages for space-constrained, thermally demanding digital systems.

FAQ

What is the maximum continuous output current per channel for the LTM4650?

The LTM4650 delivers up to 25A continuous current per output channel under specified thermal conditions (VIN = 12V, VOUT = 1.2V, TA ≤ 85°C). Derating curves in the datasheet define safe operating area based on input voltage, output voltage, and ambient temperature-e.g., at VIN = 4.5V and VOUT = 1.8V, max current drops to ~18A due to duty cycle and thermal constraints. The LTM4650 must be mounted on a 4-layer PCB with ≥2 oz copper and thermal vias to achieve full rating.

How does the LTM4650 support voltage tracking between its two outputs?

The LTM4650 uses dedicated TRACK1 and TRACK2 pins to implement precise voltage ramp sequencing. When one channel is designated "master," its TRACK pin is connected to a soft-start capacitor; the "slave" channel's TRACK pin receives a scaled version of the master's output via a resistor divider matching its feedback ratio. This ensures both outputs rise simultaneously and proportionally-critical for I/O-to-core rail sequencing in FPGAs. The LTM4650's internal 1.3µA pull-up current on each TRACK pin sets the ramp slope, and no external op-amp is needed.

Can the LTM4650 operate in single-output mode delivering 50A?

Yes-the LTM4650 supports single-output 50A operation by paralleling both channels internally. In this configuration, VOUT1 and VOUT2 are shorted together, COMP1 and COMP2 are tied, and VFB1/VFB2 are connected to a common feedback network. The device maintains current balance via internal current-mode control and requires only one set of output capacitors. Full 50A capability assumes proper thermal management: θJCbottom = 1.5°C/W must be achieved via thermal vias to inner ground planes, and peak efficiency reaches 93% at 12V input and 1.2V output.

What is the purpose of the DIFFP and DIFFN pins on the LTM4650?

The DIFFP and DIFFN pins form a differential remote sense amplifier that measures output voltage directly at the load point-not at the module's VOUT pins-to compensate for PCB trace resistance. DIFFP connects to the load's positive rail, DIFFN to the load's ground reference, and DIFFOUT feeds back to VOUTS1 or VOUTS2. This topology reduces regulation error caused by IR drop, especially critical for high-current, low-voltage rails (e.g., 0.8V @ 25A). The amplifier has 1V/V gain, 3mV offset, and 90dB PSRR-ensuring accurate sensing even with noisy system grounds.

Does the LTM4650 require external compensation components?

No-the LTM4650 is fully internally compensated and stable with a wide range of ceramic output capacitors (minimum 600µF per channel). Its current-mode architecture and built-in loop compensation eliminate the need for external Type II or Type III compensators. Stability is verified across 10–1000µF output capacitance and ESR values from 0.2mΩ to 10mΩ. Layout best practices (e.g., short COMP trace, solid SGND plane) are sufficient; no tuning resistors or capacitors are required for basic operation.