component

LM2596 (adjustable buck)

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by Ray

TI 150 kHz 3 A adjustable buck regulator, TO-263. VOUT 1.2-37 V, integrated switch. Datasheet-verified.

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Contents

README

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LM2596S-ADJ

Texas Instruments · Buck switching regulator · TO-263-5 (D2PAK)

150 kHz fixed-frequency, 3 A step-down (buck) switching regulator with an integrated high-side switch, in a TO-263-5 (D2PAK) package. The output is adjustable from 1.2 V to 37 V via a divider on the FB pin (VREF = 1.23 V). It has internal loop compensation, a TTL-compatible ON/OFF pin, thermal shutdown, and cycle-by-cycle current limit, and needs only an inductor, catch diode, and input/output capacitors. The workhorse behind countless cheap buck modules.

Pinout

Pin Name Type Function
1 VIN power_in Positive input supply for the switching regulator, 4.5 V to 40 V operating (45 V absolute max). A low-ESR bypass capacitor must be placed directly at this pin to supply the switch currents and minimize input transients.
2 Output output Internal high-side switch node (SW). Swings between approximately (VIN - VSAT) and about -0.5 V (catch-diode drop) with duty cycle VOUT/VIN; connect to the external inductor and Schottky catch diode. PCB copper area on this node must be minimized to reduce EMI coupling.
3 GND power_in Circuit ground and power return for the regulator. On the TO-263 (KTT) package the metal tab is also GND.
4 FB input Feedback input to the error amplifier, regulated to VREF = 1.23 V (typ) on the -ADJ version. Connect to the R1/R2 external divider from VOUT: VOUT = 1.23 V x (1 + R2/R1). Feedback bias current is typically 10 nA (50 nA max at 25 degC). Absolute-max range -0.3 V to 25 V.
5 ON/OFF input TTL-compatible active-low shutdown input. Pulling below ~1.3 V (or tying to GND / leaving open) enables the regulator; driving above ~1.3 V (up to 25 V max) shuts it down and drops total supply current to ~80 uA typ. Internally clamped; input current 5 uA typ at VLOGIC = 2.5 V.

Key specifications

Parameter Value
Type Buck (step-down) switching regulator
Switching frequency 150 kHz (fixed)
Output current 3 A
Output voltage 1.2-37 V adjustable (VREF 1.23 V)
Input voltage up to 40 V
Control TTL-compatible ON/OFF
Protection Thermal shutdown + cycle-by-cycle current limit
Package TO-263-5 (D2PAK)
Body (L×W×H) 10.2 × 8.4 × 4.6 mm

Ordering variants

Same part, different packaging or reel option.

The extractor listed these alongside LM2596 (adjustable buck), but they are different parts with different electrical characteristics. Do not order them as substitutes.

  • LM2596S-ADJ (TO-263, tape & reel)
  • LM2596T-ADJ (TO-220-5)

CAD (KiCad official)

  • Symbol: Regulator_Switching:LM2596S-ADJ
  • Footprint: Package_TO_SOT_SMD:TO-263-5_TabPin3
  • 3D model: TO-263-5 (KiCad packages3D)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Texas Instruments datasheet (47 pp, sha256 fbd0a8af4dcd4c37, retrieved 2026-08-17, tier: manufacturer)
  • Extractor: ds2sf (Claude) — every pin and dimension is cited to a datasheet page; refuses to fabricate.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF