Voltage Regulators & LDOsActive

LM2596

Manufacturer: Texas Instruments

Figures from the datasheet: Texas Instruments SNVS124G, rev. Rev. G, March 2023

Step-down switching voltage regulator capable of driving a 3A load with 150 kHz fixed frequency, 40V input range, internal thermal shutdown, and cycle-by-cycle current limiting in TO-220 and TO-263 packages.

PackagesTO-220-5, TO-263-5
Supply voltage4.5 – 40 V
Temperature range-40 – 125 °C
Official Datasheet (PDF)

Technical Overview

01

Technical Overview

The LM2596 is a monolithic integrated circuit manufactured by Texas Instruments (SIMPLE SWITCHER® series, Document SNVS124G, Revised March 2023) providing all active functions for a step-down (buck) switching regulator capable of driving a 3A load with excellent line and load regulation. Operating at a fixed switching frequency of 150 kHz, the LM2596 allows smaller filtering components than lower-frequency switching regulators. Available in 5-lead TO-220 (through-hole) and TO-263 (surface-mount) packages with pinout VIN, OUTPUT, GND, FEEDBACK, and ON/OFF (with the tab internally connected to GND), the device operates over a 4.5V to 40V input voltage range. It features an internal 3A NPN power switch with a typical saturation voltage of 1.16V at 3A, a 1.23V internal bandgap reference for adjustable configurations, quiescent current of 5.0 mA operating and 80 µA in shutdown mode, external shutdown via a TTL/CMOS-compatible ON/OFF pin, cycle-by-cycle current limit protection at 4.5A typical, and thermal shutdown under fault conditions.

Package Pinout & Alternate Functions

Interactive package pinout and pin mapping for TO-220-5.

Interactive pinout diagramTop

LM2596: TO-220-5 package illustrationInteractive package pinout and pin mapping for TO-220-5.1: VIN2: OUTPUT3: GND5: ON/OFF4: FEEDBACK

Package illustration, not a dimensioned mechanical drawing.

5 / 5 pins
#Pin nameType5V TolerantAlternate functions / details
VINpower in—
DC supply input voltage terminal (4.5V to 40V continuous operating range; requires low-ESR bypass capacitor located close to the IC and ground)
OUTPUTpower out—
Internal 3A NPN power switch emitter output (switches at 150 kHz between ~VIN - 1.2V and Schottky diode forward drop below ground)
GNDground—
Circuit ground reference and thermal substrate connection (internally connected to the metallic mounting tab)
FEEDBACKanalog inNo
Output voltage feedback sense terminal (senses regulated output voltage and regulates against internal 1.23V reference)
ON/OFFinput onlyYes
Shutdown control input (active-low: <= 0.6V or floating activates switching regulator; >= 2.0V up to 25V places device into 80 µA standby mode)

Key Specifications

Parametric attributes

ParameterMinTypicalMaxUnitTest condition
Oscillator Frequency(fOSC)127150173kHzVIN = 12 V, IO = 0.5 A, TJ = 25°C
Feedback Reference Voltage(VREF)1.1931.2301.267VLM2596-ADJ, VIN = 12 V, IO = 0.5 A, TJ = 25°C
Internal Switch Saturation Voltage(VSAT)—1.161.4VIOUT = 3.0 A, TJ = 25°C
Current Limit(ICL)3.64.56.9APeak switch current, TJ = 25°C
Quiescent Operating Current(IQ)—5.010mAFeedback pin = 5 V (not switching), TJ = 25°C
Standby Quiescent Current(ISTBY)—80200µAON/OFF pin = 5 V (shutdown mode), TJ = 25°C
ON/OFF Logic High Input Threshold(VIH)21.325VRegulator OFF (shutdown mode), TJ = 25°C
ON/OFF Logic Low Input Threshold(VIL)-0.31.30.6VRegulator ON (operating mode), TJ = 25°C
Maximum Continuous Output Current(IO_max)33.0—A4.5 V <= VIN <= 40 V, TJ <= 125°C with adequate heatsinking
Efficiency(eta)—82—%VIN = 12 V, VOUT = 5 V, IOUT = 3 A, TJ = 25°C

Absolute Maximum Ratings

Max supply voltage (VDD/VCC)45 V
Max input voltage25 V
Max output / pin current4500 mA
Junction temperature-40 – 125 °C
Storage temperature-65 – 150 °C
ESD rating (HBM)2000 V
Thermal resistance θJA (TO-220-5)32 °C/W
Thermal resistance θJC (TO-220-5)2 °C/W
Thermal resistance θJA (TO-263-5)36 °C/W
Thermal resistance θJC (TO-263-5)2 °C/W

Hardware Engineering Gotchas

Real-world hardware caveats, PCB layout constraints and silicon errata to know before manufacturing.

Critical

Mandatory Fast Schottky Catch Diode

The LM2596 requires a fast-recovery Schottky diode (such as 1N5822, B340A, or MBR360) across Pin 2 (OUTPUT) and ground. Using a standard slow silicon rectifier (such as 1N4001 or 1N5408) leads to excessive reverse-recovery losses, overheating, severe inductive voltage overshoot on Pin 2 during switch turn-off, and catastrophic destruction of the internal NPN switch.

Mitigation

Always specify a Schottky diode rated for at least 3A continuous average forward current (such as 1N5822 or SS34) and a reverse voltage rating of at least 1.25 times the maximum input voltage. For 24V or 36V input supplies, use a 40V or 60V Schottky barrier rectifier with ultra-short reverse recovery time (trr < 10 ns).

Critical

Critical High-Frequency Switching Ground Loop

The high-current AC switching loop consists of the input filter capacitor CIN, the internal switch (Pin 1 to Pin 2), the external Schottky catch diode, and the ground terminal (Pin 3). Because switching currents change at rates up to 3A in under 50 nanoseconds, stray PCB trace inductance creates high-frequency ringing, voltage spikes exceeding the 45V absolute maximum, and electromagnetic interference (EMI).

Mitigation

Route the input capacitor ground, Schottky diode anode, and LM2596 GND pin to a single ground point using wide, low-impedance copper pours. Keep traces between Pin 2, diode cathode, and inductor node as short as physically possible. Separate the high-current power ground from the quiet feedback node and connect them only at the output ground star point.

Warning

Output Filter Capacitor ESR Stability Boundary

The LM2596 internal voltage-mode compensation relies on the equivalent series resistance (ESR) of the output filter capacitor to provide an essential zero in the loop transfer function. Placing an ultra-low ESR ceramic capacitor (ESR < 10 mΩ) directly as the sole output capacitor without damping degrades phase margin, causing control loop instability, output ripple burst oscillations, and audible inductor whine.

Mitigation

Use low-ESR aluminum electrolytic capacitors (such as Panasonic HFQ/FC or Nichicon PL series, typically 180 µF to 680 µF with ESR between 30 mΩ and 150 mΩ) for COUT. If ceramic output capacitors are desired, place a small series damping resistor (0.05 Ω to 0.1 Ω) or parallel a 100 nF ceramic capacitor alongside a bulk electrolytic capacitor.

Warning

Internal Switch Power Dissipation at Continuous 3A Load

The internal bipolar NPN power switch exhibits a saturation voltage of approximately 1.16V to 1.4V at 3A load. At full load and moderate duty cycles, the internal switch dissipates between 2W and 3.5W as pure heat. In free air without a heatsink, the TO-220 package (thermal resistance θJA = 32°C/W) will experience a junction temperature rise of ΔTJ = 3.5W × 32°C/W = 112°C above ambient, triggering thermal shutdown (TJ > 150°C).

Mitigation

Calculate device dissipation PD = (VO × IO × VSAT) / VIN + (IQ × VIN) + switching losses. Mount the TO-220 package to an external aluminum heatsink with thermal grease (thermal resistance <= 10°C/W for 3A continuous output), or provide at least 2 square inches of 2-oz copper plane around the TO-263 tab.

Reference Circuits

LM2596 Step-Down Buck Converter (5V / 3A)

Topology: Buck (Step-Down) Switching Regulator

Inspect schematicOpen in Web CAD Editor

Official Documentation & Cited Datasheets

Primary semiconductor vendor datasheets, errata, and application notes.

DATASHEETTexas Instruments

LM2596 SIMPLE SWITCHER® Power Converter 150-kHz 3-A Step-Down Voltage Regulator

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