Texas Instruments LM2594MX-3.3/NAK2

Overview

LM2594MX-3.3/NAK2 from Texas Instruments is a monolithic nonsynchronous step-down (buck) DC-DC switching regulator delivering 3.3 V at up to 0.5 A, with 150-kHz fixed-frequency operation, ±4% output voltage tolerance over line and load, and input voltage support up to 40 V. It serves as an efficient on-card power supply for embedded microcontrollers, industrial sensors, and low-power analog circuitry.

For engineers reviewing the LM2594MX-3.3/NAK2 datasheet, LM2594MX-3.3/NAK2 pinout, LM2594MX-3.3/NAK2 application, or LM2594MX-3.3/NAK2 equivalent, key selection criteria include its SOIC-8 package, TTL-compatible ON/OFF control, 85 μA standby current, thermal shutdown protection, and requirement of only four external components for full operation.

Technical Context

The LM2594MX-3.3/NAK2 integrates a PWM controller, power switch, oscillator, error amplifier, and thermal/current protection in a single SOIC-8 package. Its fixed 150-kHz switching frequency enables predictable EMI filtering and simplifies inductor selection using standard off-the-shelf parts.

It operates in discontinuous or continuous conduction mode depending on load and inductor value, with built-in undervoltage lockout and delayed start-up capability via the ON/OFF pin - supporting system-level sequencing and input rail conditioning without external circuitry.

Key Specifications

Pinout & Package

LM2594MX-3.3/NAK2 is housed in an 8-pin SOIC (D-package) with 4.90 mm × 3.91 mm body size and standard 1.27-mm pitch. Thermal performance is characterized at R_θJA = 150°C/W on a 4-layer JEDEC board.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2594MX-3.3/NAK2, LM2594MX-3.3/NOPB offers identical functionality with enhanced environmental compliance, while LMR36506RNXR delivers superior efficiency and integration at the cost of pin compatibility and increased design effort.

Availability

LM2594MX-3.3/NAK2 is available at Aetrix Electronics and suitable for industrial sensor nodes, microcontroller core supplies, programmable logic interfaces, and legacy industrial I/O modules requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for LM2594MX-3.3/NAK2 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 technologies, with decades of experience in high-reliability industrial and automotive power solutions.

The LM2594xx series was designed specifically for cost-sensitive, medium-power DC-DC conversion in industrial controls, instrumentation, and distributed power architectures where simplicity, robustness, and minimal external component count are critical.

FAQ

What is the maximum input voltage rating for LM2594MX-3.3/NAK2?

The LM2594MX-3.3/NAK2 has a maximum input voltage rating of 40 V, as specified in the Absolute Maximum Ratings table. This applies to the standard LM2594 variant (not the HV version). Operation above 40 V risks permanent damage. The LM2594HV variant supports up to 60 V, but LM2594MX-3.3/NAK2 is not rated for that range. Always maintain at least 1-V margin below 40 V in designs with transient-prone inputs.

Does LM2594MX-3.3/NAK2 require an external feedback resistor network?

No, LM2594MX-3.3/NAK2 does not require an external feedback resistor network. As a fixed 3.3-V output version, the feedback node is internally connected to the output, eliminating the need for external resistors. This simplifies layout, reduces component count, and avoids tolerance-induced output drift. The LM2594 adjustable variant (e.g., LM2594ADJ) requires external resistors, but LM2594MX-3.3/NAK2 is fully self-contained for 3.3-V regulation.

What thermal derating applies to LM2594MX-3.3/NAK2 at 125°C ambient?

At 125°C ambient, LM2594MX-3.3/NAK2 must be thermally derated due to its R_θJA of 150°C/W. With a maximum junction temperature of 150°C, the allowable power dissipation drops to approximately 167 mW - limiting practical output current well below 0.5 A unless additional heatsinking or airflow is provided. For full 0.5-A operation at high ambient, PCB copper area, thermal vias, or forced air cooling must be implemented per TI's thermal design guidelines for the SOIC-8 package.

Can LM2594MX-3.3/NAK2 be used in an inverting (positive-to-negative) configuration?

Yes, LM2594MX-3.3/NAK2 can be configured as a positive-to-negative inverting regulator, as documented in TI's application notes (e.g., Figure 8-5). However, the fixed 3.3-V version regulates only the magnitude - the output polarity becomes negative relative to system ground. This requires re-referencing the ground pin and adding external diodes. The ON/OFF threshold shifts to ~13 V in this topology, and startup current demands increase significantly, so delayed start-up circuitry is recommended.

What is the typical efficiency of LM2594MX-3.3/NAK2 at 12-V input and 0.5-A load?

The typical efficiency of LM2594MX-3.3/NAK2 at 12-V input and 0.5-A load is 80%, as specified in Section 7.5 of the datasheet. This value assumes use of the recommended external components (e.g., Schottky catch diode, 68-μF input capacitor, 22-μF output capacitor, and appropriate inductor). Efficiency varies with input voltage, load current, and component selection - dropping at light loads due to fixed quiescent current and rising slightly at higher VIN within the 4.5–40 V range.