LM2596 Reference Tables, Pins & Specifications

Pin reference

Signal names, electrical functions and connection guidance

TO-220-5

Physical pin numbers5 pins

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LM2596 pin functions and connections
Signal	Type	Function & connection
VIN	Supply input	Supplies the internal power switch, control circuit and bias current. Connection guidance Connect the positive DC supply and a short, local input bypass to ground. The 5 V version is specified with 7–40 V input under its stated load conditions; 45 V is an absolute maximum, not an operating target.
SW	Switch node	Pulsed output of the internal high-side switch. This node drives the external inductor. Connection guidance Connect to the inductor input and Schottky cathode. The diode anode returns to GND. This is not the filtered 5 V rail. Keep switch-node copper compact and away from feedback wiring.
GND	Ground and metal tab	Common return for the controller and power stage. The exposed metal tab is also ground. Connection guidance Connect to the input-capacitor return, catch-diode anode and output-capacitor return with short power paths. On the SMD footprint, pin 3 and the thermal-pad sections have the same electrical pad number.
FB	Output sense	Senses the filtered output and closes the regulation loop. The fixed 5 V device includes its feedback divider internally. Connection guidance For the fixed 5 V example, connect directly to the output after the inductor, near COUT. The adjustable variant instead needs an external divider referenced to approximately 1.23 V. Do not mix the two circuits.
ON/OFF	Shutdown input	Low enables switching; high shuts the regulator down. Connection guidance Connect to ground for an always-on converter. Logic ON is guaranteed at 0.6 V or below and OFF at 2 V or above over the specified temperature range. The typical switching threshold is approximately 1.3 V.

Operating envelope

Fixed 5 V option · TI SNVS124G

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Nominal output	5 V	LM2596T-5.0 / LM2596S-5.0
Specified input for 5 V regulation	7–40 V	0.2–3 A output load
Output at 25°C	4.8–5.2 V	VIN = 7–40 V; ILOAD = 0.2–3 A
Output over temperature	4.75–5.25 V	Same input/load range; TJ = −40–125°C
Output current	Up to 3 A	Inductor, diode, capacitors, layout and cooling must support the load
General supply operating range	4.5–40 V	Does not imply a regulated 5 V output from 4.5 V input

Output accuracy includes the manufacturer’s stated conditions; do not use a headline current rating without thermal review.

Switching and control

Typical values retain their test conditions

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Oscillator	150 kHz typical	127–173 kHz at 25°C; 110–173 kHz over temperature
Switch saturation	1.16 V typical	3 A switch current; 1.4 V maximum at 25°C
Peak switch-current limit	4.5 A typical	Protection threshold; not a continuous output rating
Shutdown threshold	1.3 V typical	High = OFF; low = ON
Guaranteed enable / shutdown	≤ 0.6 V / ≥ 2 V	Logic thresholds over specified temperature range
Standby supply current	80 µA typical	VIN = 40 V, ON/OFF = 5 V; 200 µA maximum at 25°C

The internal switch and diode have losses; the actual duty ratio is above the ideal VOUT/VIN estimate.

12 V to 5 V example

Nominal 1 A load · illustrative component selection

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Input / output	12 V DC / 5 V DC	Fixed-output device; pin 4 connected directly to filtered output
Inductor L1	47 µH	Choose saturation/current ratings for load, ripple and current-limit behavior
Catch diode D1	1N5825 · 5 A, 40 V Schottky	Cathode to pin 2; anode to GND; suitable for this 12 V illustration
Input CIN	470 µF, 50 V	Low-ESR aluminum; check RMS ripple rating
Output COUT	330 µF, 35 V	Low-ESR aluminum; check TI ESR/stability guidance
Load	5 Ω · at least 10 W	1 A nominal; resistor dissipates 5 W

The inductor, diode and capacitor values follow TI’s layout example. Validate startup, ripple, stability and thermal margins for the actual parts and conditions.

Understand the waveforms

Ideal continuous-conduction estimates

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Duty ratio	D ≈ 5 / 12 = 41.7%	Neglects switch and diode voltage drops
Switch period	6.67 µs	1 / 150 kHz
ON time	2.78 µs	D / f
Inductor ripple	Approximately 0.414 A peak-to-peak	(12 − 5) × D / (47 µH × 150 kHz)
Peak current at 1 A average	Approximately 1.207 A	ILOAD + ΔIL/2 in ideal steady state
Output power	5 W	5 V × 1 A

This calculation is a teaching aid. It is not a full SPICE simulation or a guarantee of measured ripple.

Layout and package checks

Short switching loops · correct thermal-pad mapping

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Input loop	CIN → VIN → internal switch → diode → CIN return	Place CIN and diode close to the IC
Switch node	Pin 2 to L1 and diode cathode	Keep copper compact and away from feedback
Feedback	Pin 4 to COUT positive / output	Use a quiet sense route, away from switch node
Ground / tab	Pin 3 plus exposed metal tab	Ground plane and cooling path
TO-220 footprint	NDH formed-lead pattern	1.70 mm lateral pitch; 5.80 mm nominal row stagger
D²PAK footprint	KTT five leads plus stepped thermal land	All pad-3 sections are GND

The downloads contain electrical pads and outlines. Check the chosen lead form, solder process and heatsinking before manufacture.

Thermal and stress limits

Separate operating conditions from stress ratings

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Operating junction temperature	−40 to +125°C	Recommended range
Supply absolute maximum	45 V	Stress rating; recommended VIN maximum is 40 V
Junction absolute maximum	150°C	Not a normal operating target
Storage temperature	−65 to +150°C	Unpowered
TO-220 RθJA	50°C/W	Vertical mount; approximately 1 in², 1 oz copper per TI note
TO-263 RθJA	20–50°C/W in TI examples	Depends strongly on copper area and board conditions

Thermal shutdown and current limiting provide protection; they do not replace a suitable board and cooling design.