Texas Instruments LM25005MHX

Overview

LM25005MHX from Texas Instruments is a 42V, 2.5A synchronous step-down DC/DC switching regulator with integrated 160mΩ N-channel MOSFET, current-mode control using emulated ramp, and programmable 50–500kHz oscillator. It delivers regulated output down to 1.225V and supports industrial point-of-load conversion from 7V–42V input rails.

For engineers reviewing the LM25005MHX datasheet, LM25005MHX pinout, LM25005MHX application, or LM25005MHX equivalent, key selection criteria include its 42V input rating, thermal shutdown at 165°C, ±1.5% feedback reference accuracy, HTSSOP-20 package with exposed pad, and synchronization capability for multi-rail systems.

Technical Context

The LM25005MHX implements peak current-mode control via an emulated inductor current ramp-generated by internal voltage-controlled current source (18–184µA depending on VIN/VOUT) and external RAMP capacitor-eliminating noise-sensitive current sensing and enabling stable operation at small duty cycles. Its dual-mode VCC bias regulator maintains 7V output above 9V VIN while tracking VIN below that threshold.

Functional modes are controlled via the SD pin: <0.7V = shutdown (<85µA quiescent), 0.7–1.225V = standby (bias active, switch disabled), >1.225V = full operation. Synchronization occurs bidirectionally on the SYNC pin, allowing multiple LM25005MHX units to lock to the highest-frequency device without external clock sources.

Key Specifications

Pinout & Package

LM25005MHX is housed in a thermally enhanced 20-pin HTSSOP (PWP) package measuring 6.5mm × 4.4mm with exposed die attach pad (EP) soldered to PCB ground plane for low RθJC(bot) = 1.2°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Compared with LM5115MHX and TPS54240DGQR, the LM25005MHX uniquely integrates both high-voltage switching and emulated current-mode control in a single 20-pin HTSSOP, reducing component count while maintaining precision regulation and robust fault handling for industrial 2.5A loads.

Availability

LM25005MHX is available at Aetrix Electronics and suitable for industrial point-of-load regulators, telecom infrastructure power shelves, and factory automation I/O modules requiring stable component supply, long-term lifecycle support, and consistent parametric performance.

Supply support for LM25005MHX 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management ICs, with decades of expertise in high-reliability power conversion solutions.

The LM25005MHX belongs to TI's high-voltage DC/DC controller family designed specifically for efficient, compact buck regulation in industrial, telecom, and automotive environments where input voltage exceeds 36V.

FAQ

What is the maximum input voltage rating for the LM25005MHX?

The LM25005MHX has an absolute maximum input voltage rating of 45V, with recommended operating range from 7V to 42V. Exceeding 45V-even transiently-can cause permanent damage. Layout best practices include placing high-quality input capacitors close to the VIN and PGND pins to suppress ringing during load or line transients. The LM25005MHX is engineered for reliable operation across harsh industrial 24V and telecom 48V bus environments within this specification.

How does the LM25005MHX achieve current-mode control without a sense resistor?

The LM25005MHX uses an emulated current ramp architecture: it samples freewheeling diode current at the IS pin to establish a DC level, then generates a voltage-controlled ramp signal at the RAMP pin using an internal current source (5µA/V × (VIN − VOUT) + 25µA). This eliminates external sense resistors and associated power loss/noise. The LM25005MHX thus achieves true current-mode benefits-including inherent line feed-forward and simplified loop compensation-without compromising efficiency or board space.

Can the LM25005MHX synchronize multiple regulators without an external clock source?

Yes. The LM25005MHX SYNC pin operates bidirectionally: when multiple LM25005MHX devices have their SYNC pins tied together, the unit with the highest programmed oscillator frequency (set by its RT resistor) automatically becomes the master and forces all others into slave mode. No external clock generator is needed. This self-synchronizing capability simplifies multi-rail designs and reduces EMI through deterministic phase alignment-core functionality confirmed in the LM25005MHX datasheet Figure 6-4.

What thermal performance can be expected from the LM25005MHX in a standard 4-layer PCB layout?

In a standard 4-layer PCB with 2oz copper, 1-in² exposed EP pad connected to inner ground planes, the LM25005MHX achieves RθJA ≈ 35.2°C/W and RθJC(bot) ≈ 1.2°C/W. At 2.5A output and 24V input, typical junction temperature rise is ~88°C above ambient-well within the 125°C max operating limit. The LM25005MHX thermal design relies critically on proper EP pad soldering; insufficient thermal vias or missing ground connections will significantly degrade performance and trigger thermal shutdown.

Does the LM25005MHX support adjustable soft-start timing, and how is it implemented?

Yes. The LM25005MHX implements soft-start via a precision 10µA internal current source charging an external capacitor connected to the SS pin. The resulting voltage ramp controls the error amplifier reference, delaying full output regulation. Start time is calculated as tSS ≈ (CSS × 1.225V) / 10µA. For example, a 100nF capacitor yields ~12ms soft-start. The LM25005MHX also discharges the SS capacitor during faults (e.g., thermal shutdown or VCC UVLO), ensuring safe restart after recovery.