Analog Devices Inc. LT1580IR-2.5#PBF

Overview

LT1580IR-2.5#PBF from Analog Devices (formerly Linear Technology) is a 7A fixed-output low-dropout linear regulator with 2.5V output, remote sense capability, and dual-supply architecture requiring separate VCONTROL and VPOWER inputs. It delivers 1mV load regulation over 100mA–7A, achieves 540mV dropout at full load, and targets high-current microprocessor core supplies on motherboards using available 3.3V/5V rails.

For engineers reviewing the LT1580IR-2.5#PBF datasheet, LT1580IR-2.5#PBF pinout, LT1580IR-2.5#PBF application, or LT1580IR-2.5#PBF equivalent, this page provides verified technical context, package-specific pin functions, real-world transient response behavior, thermal design constraints, and validated alternative options for 2.5V/7A processor supply implementations.

Technical Context

The LT1580IR-2.5#PBF uses a dual-input architecture: VCONTROL (≥1.0V above VOUT) powers control circuitry and supplies ~1% of output current as base drive, while VPOWER (≥0.1V above VOUT) supplies the NPN pass transistor collector. This separates drive and power paths to minimize dropout-achieving just 540mV at 7A-unlike single-supply LDOs.

It implements Kelvin remote sensing via dedicated SENSE and GND pins to eliminate PCB trace IR drop effects, enabling <1mV load regulation measured at the load. The ADJ pin is exposed on this fixed-output variant to allow external capacitor bypassing (0.1–1µF), improving transient response and ripple rejection without altering output voltage.

Key Specifications

Pinout & Package

LT1580IR-2.5#PBF is housed in a 7-lead plastic TO-220 (T7) package with exposed tab (thermal path). Pin 1 is SENSE, Pin 2 is ADJ, Pin 3 is VPOWER, Pin 4 is VOUT, Pin 5 is VCONTROL, Pin 6 is GND, Pin 7 is NC (no connect). The tab is electrically connected to VOUT and serves as primary thermal interface.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-current, low-dropout linear regulator applications.

Compared with LTC3085EDD-2.5#PBF and TPS7A8300RGRT, the LT1580IR-2.5#PBF uniquely combines 7A output, remote Kelvin sensing, and dual-supply architecture-making it irreplaceable where load-point accuracy under high dynamic current is non-negotiable, despite requiring two input rails.

Availability

LT1580IR-2.5#PBF is available at Aetrix Electronics and suitable for microprocessor core supplies, FPGA I/O banks, post-regulation of switching converters, and portable computing power systems requiring stable component supply and long-term industrial availability.

Supply support for LT1580IR-2.5#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 ICs, serving industrial, automotive, communications, and computing markets.

The LT1580 product line was designed specifically for high-current, low-dropout microprocessor core regulation-addressing the need for sub-1V input/output differential, remote sensing, and robust transient response in late-1990s Pentium® and PowerPC™ platforms.

FAQ

What is the minimum input voltage required for LT1580IR-2.5#PBF to regulate at 7A?

The LT1580IR-2.5#PBF requires two separate input voltages: VPOWER must be at least 0.70–0.80V above 2.5V (i.e., ≥3.2V) at 7A and 0°C–125°C, while VCONTROL must be at least 1.15–1.30V above 2.5V (i.e., ≥3.65V). Both rails must be present simultaneously-neither alone suffices. These values are specified in the Electrical Characteristics table under "Minimum VPOWER" and "Minimum VCONTROL".

Can LT1580IR-2.5#PBF operate from a single input supply?

Yes, LT1580IR-2.5#PBF can operate with VCONTROL and VPOWER tied together, functioning as a conventional single-supply LDO-but dropout increases to match that of the LT1584 (≈1.0V at 7A), losing the key advantage of its dual-supply architecture. Thermal performance also degrades due to combined power dissipation in one path. Datasheet Section "Applications Information" explicitly confirms this mode but notes it sacrifices optimized dropout.

Why does LT1580IR-2.5#PBF expose the ADJ pin despite being a fixed 2.5V device?

The ADJ pin is exposed on LT1580IR-2.5#PBF to allow connection of a 0.1–1µF capacitor to ground, which lowers high-frequency output impedance and improves transient response-critical for microprocessor loads with nanosecond-scale current steps. This feature, uncommon in fixed-output LDOs, leverages the internal resistor divider's node without altering the 2.5V setpoint. Datasheet Figure 1 and Applications Information confirm this design intent.

How does remote sensing work on LT1580IR-2.5#PBF, and what is its practical benefit?

LT1580IR-2.5#PBF uses dedicated SENSE and GND pins to close the feedback loop directly at the load terminals-not at the regulator output. This eliminates voltage errors caused by PCB trace resistance (e.g., 5mΩ × 7A = 35mV drop). As confirmed in the Electrical Characteristics table, load regulation is ≤1mV over 100mA–7A when measured at SENSE, enabling true point-of-load accuracy essential for modern microprocessors.

What thermal considerations apply to LT1580IR-2.5#PBF in continuous 7A operation?

At 7A with 0.8V dropout (VPOWER = 3.3V), LT1580IR-2.5#PBF dissipates ≈5.6W in the power transistor (P = 0.8V × 7A). With θ_JA = 50°C/W (T7 package), ambient must stay below ≈74°C to keep junction ≤150°C. A heatsink reducing θ_CA to ≤10°C/W is strongly recommended. Datasheet Table "Thermal Resistance" specifies 2.70°C/W (junction-to-case) for the power section-mounting to a thermally conductive surface is mandatory.