Texas Instruments LM2594MX-3.3

Overview

LM2594MX-3.3 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 (LM2594 variant). It serves as an efficient on-card power supply for microcontroller cores, FPGA I/O banks, and industrial sensor interfaces requiring stable low-noise 3.3-V rails.

For engineers reviewing the LM2594MX-3.3 datasheet, LM2594MX-3.3 pinout, LM2594MX-3.3 application, or LM2594MX-3.3 equivalent, key selection criteria include its 0.5-A guaranteed output current, 85-μA standby quiescent current in shutdown, SOIC-8 surface-mount package, and compatibility with standard off-the-shelf inductors - all critical for cost-sensitive, space-constrained embedded power designs.

Technical Context

The LM2594MX-3.3 integrates a PWM controller, power switch, oscillator, and internal frequency compensation in a single chip. Its architecture uses external diode, inductor, and capacitors to form a classic nonsynchronous buck topology, with feedback sensed directly at the output via the internal 1.23-V reference and dedicated Feedback pin.

It operates in continuous conduction mode by default but supports discontinuous mode at light loads; thermal shutdown and peak-current limiting provide fault protection. The ON/OFF pin enables logic-level shutdown with 1.3-V threshold and 85-μA standby current, while the fixed 150-kHz switching frequency simplifies EMI filtering and inductor selection.

Key Specifications

Pinout & Package

LM2594MX-3.3 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 with 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 LM2594N-3.3, LM2594MX-3.3 provides superior thermal performance in surface-mount layouts and smaller footprint; compared with LM2594HVX-3.3, it trades 20-V input headroom for lower quiescent current and optimized cost in 12–24-V applications.

Availability

LM2594MX-3.3 is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, and medical diagnostics requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for LM2594MX-3.3 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 expertise in reliable, high-volume power conversion ICs.

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

FAQ

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

The LM2594MX-3.3 has a maximum input voltage rating of 40 V, as specified in the Absolute Maximum Ratings table. This distinguishes it from the LM2594HVX-3.3 variant, which supports up to 60 V. Exceeding 40 V on the +VIN pin of the LM2594MX-3.3 risks permanent damage, even momentarily. Designers must ensure transient suppression (e.g., TVS diodes) limits input spikes within this limit.

Does the LM2594MX-3.3 require an external feedback resistor network?

No, the LM2594MX-3.3 does not require external feedback resistors. As a fixed-output variant, it internally regulates to 3.3 V using a precision 1.23-V reference and dedicated feedback amplifier. Pin 4 (Feedback) connects directly to the output node, completing the loop without external components - a key simplification versus the adjustable LM2594ADJ version.

What is the typical efficiency of the LM2594MX-3.3 at full load?

The LM2594MX-3.3 achieves 80% typical efficiency at VIN = 12 V and IOUT = 0.5 A, per Section 7.5 of the datasheet. Efficiency varies with input voltage and load: it rises to ~88% at higher VIN (e.g., 24 V → 3.3 V) and drops at lighter loads due to fixed switching losses. Real-world efficiency depends on external component selection - especially Schottky diode forward voltage and inductor DCR.

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

Yes, the LM2594MX-3.3 can be configured as a positive-to-negative inverting regulator, as documented in Figure 8-5 of the datasheet. In this topology, the GND pin floats at the negative output voltage, and the Feedback pin is grounded. However, the maximum voltage across the IC becomes |VIN| + |VOUT|, so for a −3.3-V output, VIN must be limited to ≤36.7 V to stay within the 40-V absolute maximum rating.

What thermal considerations apply to the LM2594MX-3.3 in SOIC-8 package?

The LM2594MX-3.3 in SOIC-8 has a junction-to-ambient thermal resistance (R_θJA) of 150°C/W on a standard 4-layer JEDEC board. At 0.5-A load and 12-V input, power dissipation is ~4.35 W, implying a worst-case junction rise of 653°C - clearly unsustainable. Practical designs require generous copper pour on the GND pin, thermal vias under the exposed pad (if present), and derating above ~0.25 A unless ambient is <40°C or forced airflow is used.