Texas Instruments LM2599T-12/NOPB

Overview

LM2599T-12/NOPB from Texas Instruments is a monolithic 150-kHz nonsynchronous step-down DC-DC converter delivering up to 3 A output current with fixed 12-V output, ±4% output voltage tolerance over line and load, and input voltage range up to 40 V. It integrates internal frequency compensation, thermal shutdown, current-limit protection, and soft-start/shutdown control - used in industrial power supplies and embedded system point-of-load regulation.

For engineers reviewing the LM2599T-12/NOPB datasheet, LM2599T-12/NOPB pinout, LM2599T-12/NOPB application, or LM2599T-12/NOPB equivalent, key selection criteria include its fixed 12-V output, TO-220-7 package thermal performance (R_θJA = 50°C/W), 80-μA standby current, and integrated error flag with programmable delay for power-good signaling.

Technical Context

The LM2599T-12/NOPB operates as a fixed-frequency (150 kHz) buck regulator using an internal NPN switch and external catch diode, inductor, and capacitors. Its feedback loop senses output voltage via internal 1.23-V reference and adjusts duty cycle to maintain regulation across 4.5–40 V input and –40°C to +125°C ambient.

Functional modes include normal regulation, shutdown (80 μA I_Q), soft-start (capacitor-controlled ramp), and out-of-regulation detection with open-collector error flag and delay timing. Protection includes two-stage current limit, thermal shutdown, and input overvoltage clamping.

Key Specifications

Pinout & Package

LM2599T-12/NOPB is supplied in a 7-pin TO-220 package (NDZ) with vertical mounting and tab-connected to Pin 4 (Ground). The exposed tab provides thermal conduction to heatsink or PCB copper area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2596T-12/NOPB, LM2599T-12/NOPB adds critical system-level features (error flag, delay, soft-start) without increasing BOM count; versus LM2678-12/NOPB, it trades peak current headroom for simpler layout, lower EMI, and plug-and-play operation in 3-A applications.

Availability

LM2599T-12/NOPB is available at Aetrix Electronics and suitable for industrial PLC power supplies, automotive body control modules, and POS terminal power management requiring stable component supply and long-term manufacturability.

Supply support for LM2599T-12/NOPB 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 high-reliability power conversion ICs.

The LM2599 series belongs to TI's SIMPLE SWITCHER® portfolio - designed specifically for engineers needing robust, easy-to-implement DC-DC solutions with minimal external components and proven thermal performance in industrial and automotive environments.

FAQ

What is the maximum input voltage rating for LM2599T-12/NOPB?

The LM2599T-12/NOPB has an absolute maximum input voltage rating of 45 V, with recommended operating range from 4.5 V to 40 V. Exceeding 40 V during normal operation risks violating safe operating area limits, especially under high ambient temperature or poor heatsinking - sustained operation above this level may trigger thermal shutdown or reduce lifetime reliability. Always verify worst-case input conditions including transients when designing with LM2599T-12/NOPB.

Does LM2599T-12/NOPB require an external feedback resistor network?

No, LM2599T-12/NOPB does not require external feedback resistors. As a fixed-output variant, it internally sets the regulated output to 12 V using a precision 1.23-V reference and trimmed resistor ratio. Pin 6 (Feedback) must be left unconnected per the datasheet - connecting external components to this pin will disrupt regulation and cause output voltage deviation. This simplifies layout and improves long-term stability compared to adjustable versions.

How does the Error Flag pin function in LM2599T-12/NOPB?

The Error Flag pin (Pin 3) of LM2599T-12/NOPB is an open-collector output that pulls low when the regulated output voltage falls more than 5% below nominal (i.e., below 11.4 V). At startup, it remains low until VOUT reaches 95% of 12 V and the Delay pin capacitor charges - then transitions high after a user-defined delay. This provides a clean, debounced power-good signal usable for microcontroller reset or system supervision without external circuitry.

Can LM2599T-12/NOPB be used in an inverting (positive-to-negative) configuration?

Yes, LM2599T-12/NOPB can be configured as an inverting regulator to generate a negative output (e.g., –12 V) from a positive input, using the topology shown in TI's SLVA017 application note. This requires relocating the ground reference, adding an isolation diode, and selecting appropriate inductor/capacitor values. Note that maximum output current depends on both input and output voltage magnitudes, and the total voltage across the IC must remain ≤40 V - so 24-V input yields ≤16-V |V_OUT| in practice.

What thermal considerations apply to LM2599T-12/NOPB in TO-220 package?

LM2599T-12/NOPB in the TO-220-7 (NDZ) package has a junction-to-ambient thermal resistance (R_θJA) of 50°C/W with no heatsink. To maintain T_J ≤125°C at full 3-A load and 40-V input (worst-case power dissipation ~20 W), a heatsink reducing R_θJA to ≤20°C/W is required. Mounting the tab to ≥1 in² of 1-oz copper with thermal vias significantly improves performance - always verify temperature rise under actual operating conditions using LM2599T-12/NOPB's thermal shutdown threshold (150°C).