Texas Instruments LM2594N-12

Overview

LM2594N-12 from Texas Instruments is a monolithic nonsynchronous step-down (buck) DC-DC switching regulator delivering 12 V at up to 0.5 A with ±4% output voltage tolerance, 150-kHz fixed-frequency operation, and input voltage support up to 40 V. It integrates PWM controller, power switch, and protection circuitry for compact, high-efficiency on-card power conversion in industrial and embedded systems.

For engineers reviewing the LM2594N-12 datasheet, LM2594N-12 pinout, LM2594N-12 application, or LM2594N-12 equivalent, key selection criteria include its 12-V fixed output, PDIP-8 package thermal performance (R_θJA = 95°C/W), TTL-compatible ON/OFF control, 85-μA standby current, and compatibility with standard off-the-shelf inductors.

Technical Context

The LM2594N-12 operates in continuous conduction mode by default, using internal frequency compensation and a fixed 150-kHz oscillator to regulate output via duty-cycle control of an integrated NPN power switch. Its feedback loop senses output through an internal 1.23-V reference and external resistor divider (not required for fixed 12-V version).

Protection includes two-stage current limiting (peak limit ≈ 0.8 A) and thermal shutdown. The ON/OFF pin enables logic-level shutdown with 1.3-V threshold and 85-μA standby quiescent current, while saturation voltage (V_SAT) remains ≤1.1 V at 0.5-A load.

Key Specifications

Pinout & Package

LM2594N-12 is supplied in an 8-pin plastic dual in-line package (PDIP) with body size 9.81 mm × 6.35 mm. Pin 1–3 are no-connect (NC) but must be soldered to PCB for thermal relief. The package provides adequate thermal performance for 0.5-A operation without forced airflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2594HVN-12, the LM2594N-12 trades input voltage headroom for lower cost and identical thermal behavior in PDIP-8; compared with LM2596-12, it offers proven reliability in through-hole industrial assemblies but lacks current scalability.

Availability

LM2594N-12 is available at Aetrix Electronics and suitable for industrial sensor nodes, legacy equipment upgrades, on-board microcontroller supplies, and positive-to-negative converter designs requiring stable component supply, long-term manufacturability, and through-hole assembly compatibility.

Supply support for LM2594N-12 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 heritage in switching regulator design and manufacturing.

The LM2594xx series was developed for cost-sensitive, high-reliability industrial and embedded power applications where simplicity, thermal robustness, and minimal external component count are critical design requirements.

FAQ

What is the maximum input voltage rating for the LM2594N-12?

The LM2594N-12 has an absolute maximum input voltage of 45 V and a recommended operating maximum of 40 V. Exceeding 40 V risks violating recommended conditions and may trigger internal protection or reduce long-term reliability. For 48-V or higher input systems, the LM2594HVN-12 variant - rated for 60-V input - is the appropriate alternative. Always observe derating guidelines in TI's SNVS118F datasheet for LM2594N-12.

Does the LM2594N-12 require external feedback resistors to set its output voltage?

No, the LM2594N-12 does not require external feedback resistors because it is a fixed 12-V output variant. Its internal feedback network is trimmed to deliver 12 V ±4% across line, load, and temperature. Pin 4 (Feedback) is internally connected and should be left unconnected or bypassed to ground per layout recommendations - unlike the adjustable LM2594ADJ version, which relies on external resistor dividers.

Can the LM2594N-12 be used in an inverting (positive-to-negative) configuration?

Yes, the LM2594N-12 can be configured as a positive-to-negative converter by re-biasing its ground pin to the negative output rail, as documented in TI's SNVS118F datasheet Figure 8-5. This topology generates −12 V from a +24-V input, but requires additional diodes (D1, D3), careful start-up sequencing, and attention to maximum voltage stress (input + |output| ≤ 40 V). The LM2594N-12's fixed 12-V reference remains functional in this mode.

What is the thermal resistance (R_θJA) of the LM2594N-12 in its PDIP-8 package?

The LM2594N-12 in the PDIP-8 package has a junction-to-ambient thermal resistance (R_θJA) of 95°C/W under JEDEC-standard 4-layer board conditions. This value assumes proper PCB copper pour on the ground pin and no forced airflow. At 0.5-A load and 24-V input, typical power dissipation is ~0.3 W, resulting in ~28.5°C junction rise above ambient - well within the 150°C maximum junction temperature limit.

How does the ON/OFF pin function on the LM2594N-12?

The ON/OFF pin (Pin 5) of the LM2594N-12 provides TTL-compatible shutdown control: pulling it below ~1.3 V (referenced to ground) enables regulation, while pulling it above ~1.3 V disables switching and reduces quiescent current to 85 μA. It accepts logic-high voltages up to 25 V and draws only 5–15 μA. If unused, the pin may be tied directly to ground to ensure always-on operation - no pull-up or pull-down resistors are required.