Texas Instruments LM2599T-5.0

Overview

LM2599T-5.0 from Texas Instruments is a monolithic 150-kHz nonsynchronous step-down DC-DC converter delivering up to 3 A output current with fixed 5-V output, ±4% regulation over line and load, input voltage range up to 40 V, and integrated thermal shutdown and current-limit protection - used in industrial power supplies and embedded system point-of-load conversion.

For engineers reviewing the LM2599T-5.0 datasheet, LM2599T-5.0 pinout, LM2599T-5.0 application, or LM2599T-5.0 equivalent, key selection criteria include output accuracy under wide input variation, soft-start control for inrush limiting, error flag timing behavior, and TO-220 thermal performance at full load.

Technical Context

The LM2599T-5.0 implements a fixed-frequency (150 kHz) buck topology with internal power switch, requiring only external diode, inductor, and capacitors. Its feedback loop senses output via internal 1.23-V reference and adjusts duty cycle to maintain regulation across 7 V–40 V input and 0.2 A–3 A load.

Functional modes include active regulation, shutdown (80 μA standby), soft-start (capacitor-controlled ramp), and out-of-regulation detection with programmable delay. Protection includes two-stage current limit, thermal shutdown, and undervoltage lockout capability via SD/SS pin threshold (1.3 V).

Key Specifications

Pinout & Package

LM2599T-5.0 is supplied in a 7-pin TO-220 package (body size 14.986 mm × 10.16 mm) with vertical lead orientation and integral heat sink tab. The package requires mounting to a heatsink or copper pour for continuous 3-A operation at ambient >50°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2596T-5.0 and MP1584EN-LF-Z, the LM2599T-5.0 uniquely combines 3-A capability, integrated error flag with delay, and TO-220 thermal performance - making it optimal for industrial and automotive applications requiring robust fault handling without added components.

Availability

LM2599T-5.0 is available at Aetrix Electronics and suitable for industrial power supplies, embedded system rails, and automotive body control modules requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM2599T-5.0 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 power management technologies.

The LM2599 series belongs to TI's SIMPLE SWITCHER® power converter family, designed specifically for ease-of-use in non-isolated DC-DC buck applications where minimal external components, thermal robustness, and integrated supervision features are critical.

FAQ

What is the maximum input voltage rating for the LM2599T-5.0?

The LM2599T-5.0 has an absolute maximum input voltage rating of 45 V, with recommended operating range from 4.5 V to 40 V. Exceeding 40 V in normal operation risks violating safe operating area limits, especially under high ambient temperatures or poor heatsinking - sustained operation above this level may trigger thermal shutdown or cause premature device failure. Always verify input transient conditions against the 45-V absolute max.

Does the LM2599T-5.0 require an external feedback resistor network?

No, the LM2599T-5.0 does not require external feedback resistors because it is a fixed-output variant with internal voltage divider set to 5.0 V. Pin 6 (Feedback) must be left unconnected per the datasheet - connecting it externally would disrupt regulation and potentially cause output instability or overvoltage. This simplifies design and improves accuracy versus adjustable versions.

How does the Error Flag pin function in the LM2599T-5.0?

The Error Flag pin (Pin 3) is an open-collector output that pulls low when the regulated 5-V output drops more than 5% below nominal (i.e., below 4.75 V). It remains low during startup until V_OUT reaches 95% of 5 V and the Delay pin capacitor charges - then transitions high. This signal can directly drive microcontroller reset inputs or supervisory circuits without additional level-shifting components.

Can the LM2599T-5.0 be used in an inverting (positive-to-negative) configuration?

Yes, the LM2599T-5.0 supports inverting configurations to generate −5 V from a positive input, as documented in TI's application notes. In this topology, the ground pin is referenced to the negative output, and the feedback pin is grounded - the regulator senses the inverted voltage. Input-to-ground voltage must remain ≤40 V, and startup inrush current is higher; soft-start is strongly recommended to manage peak input demand.

What thermal considerations apply to the LM2599T-5.0 in TO-220 package?

The LM2599T-5.0 in TO-220 (NDZ) has a junction-to-ambient thermal resistance (R_θJA) of 50°C/W with no heatsink. At 3 A output and 12 V input, power dissipation exceeds 2 W - requiring either a heatsink or ≥1 in² copper pour to maintain junction temperature below 125°C. Thermal shutdown activates at 150°C, so derating is essential for reliable long-term operation in enclosed or high-ambient environments.