Texas Instruments LM3460M5X-1.5

Overview

LM3460M5X-1.5 from Texas Instruments is a precision shunt regulator IC designed for GTLp bus termination at 1.5 V, featuring ±1% regulated voltage tolerance, 1.5 V nominal output (1.485–1.530 V), 85 μA quiescent current, 3.3 mA/mV transconductance, and operation in the 0°C to +70°C ambient range. It functions as the control element in high-current linear regulators delivering up to 7 A with external NPN pass transistors.

For engineers reviewing the LM3460M5X-1.5 datasheet, LM3460M5X-1.5 pinout, LM3460M5X-1.5 application, or LM3460M5X-1.5 equivalent, this device serves as a precision voltage reference and error amplifier in feedback loops for GTL/GTLp bus termination and adjustable high-current linear regulation - requiring attention to compensation capacitor selection, thermal management of the external pass transistor, and IN-to-GND sensing topology.

Technical Context

The LM3460M5X-1.5 implements a trimmed bandgap reference with curvature correction for low temperature coefficient (<50 ppm/°C implied by ±1% over 0°C–70°C), driving an internal op amp whose output sources current into the base of an external NPN pass transistor. Its COMPENSATION pin provides direct access to the inverting input for loop stability tuning via a single capacitor to OUT.

It operates as a two-terminal shunt regulator: voltage is sensed between IN and GROUND; when IN reaches VREG (1.5 V), the OUT pin sources current to reduce drive to the external pass transistor, establishing negative feedback. The 5-pin SOT23 package includes dedicated pins for IN, OUT, GROUND, COMPENSATION, and NC (thermally connected but unconnected).

Key Specifications

Pinout & Package

LM3460M5X-1.5 is housed in a thermally enhanced 5-lead SOT23-5 (Package Number MF05A) with Pin 5 internally unconnected but recommended for soldering to PCB ground plane for improved heat transfer.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar shunt regulator applications.

Compared with LM3460M5X-1.2 and TLV431ACDBVR, the LM3460M5X-1.5 delivers uniquely optimized performance for GTLp termination - including guaranteed 1.5 V output, COMP pin for stability tuning, and verified ≤30 µs transient recovery - making it irreplaceable in high-speed bus designs despite its obsolescence status.

Availability

LM3460M5X-1.5 is available at Aetrix Electronics and suitable for GTLp bus termination, high-current linear regulation, and precision adjustable reference applications requiring stable component supply despite TI's obsolete status.

Supply support for LM3460M5X-1.5 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 company headquartered in Dallas, Texas, specializing in analog, embedded processing, and digital signal technologies for industrial, automotive, and communications markets.

The LM3460 product line was developed specifically for precision GTL and GTLp bus termination in high-speed computing infrastructure, emphasizing low-noise reference stability, fast transient response, and compact SOT23 integration with discrete power transistors.

FAQ

What is the primary function of the LM3460M5X-1.5 in a circuit?

The LM3460M5X-1.5 functions as a precision shunt regulator that senses voltage at its IN pin relative to GROUND and sources current from its OUT pin when that voltage reaches 1.5 V. This current controls the base drive of an external high-current NPN transistor, forming a closed-loop system to maintain a stable 1.5 V output - essential for GTLp bus termination and high-current linear regulation. The LM3460M5X-1.5 does not regulate directly but enables regulation through external components.

Can the LM3460M5X-1.5 be used for voltages other than 1.5 V?

Yes - the LM3460M5X-1.5 supports adjustable output voltages using an external resistive divider connected to its IN and GROUND pins. Texas Instruments specifies that RA should be less than 500 Ω and 1% tolerance resistors used to maintain accuracy. The LM3460M5X-1.5's internal reference and amplifier remain fixed, but the feedback network shifts the regulation point; however, performance (e.g., noise, transient response) is validated only for 1.5 V per the datasheet.

Why does the LM3460M5X-1.5 have a COMP pin, and how is it used?

The COMP pin exposes the inverting input of the internal error amplifier, allowing direct external compensation for loop stability. In standard use, a single capacitor is connected from COMP to OUT to control phase margin and prevent ringing during load transients. This design enables tuning for specific pass transistor characteristics and output capacitance, which is critical for achieving the documented <30 µs recovery time in the LM3460M5X-1.5's 7 A application.

Is the LM3460M5X-1.5 still in production, and what does "OBSOLETE" mean for this part?

Texas Instruments has marked the LM3460M5X-1.5 as OBSOLETE per the SNVS126D datasheet revision history, indicating no new manufacturing. However, Aetrix Electronics maintains legacy inventory with full traceability and supports ongoing production programs requiring this exact specification. Obsolescence does not affect electrical performance or reliability - all published parameters (±1% tolerance, 3.3 mA/mV Gm, 50 μV RMS noise) remain valid for units in stock.

How does thermal management work for the LM3460M5X-1.5 given its SOT23-5 package?

The LM3460M5X-1.5 uses Pin 5 as a thermal pad with no internal connection - it must be soldered to a PCB ground plane to dissipate heat effectively. With a typical θ_JA of 330°C/W, even modest power dissipation (e.g., 100 mW) raises junction temperature significantly. Therefore, the LM3460M5X-1.5 itself handles only control current (≤20 mA), while heat from the main 7 A load is borne by the external pass transistor - making proper heatsinking of Q4 (not the LM3460M5X-1.5) the dominant thermal concern.