Overview

The LM2596 (and surface-mount TO-263 packaged LM2596S-ADJ) is a 3.0 Amp step-down (buck) switching voltage regulator IC manufactured by Texas Instruments. Sold as a ubiquitous blue DC-DC buck converter breakout module with a multi-turn trimmer potentiometer on Amazon, eBay, and AliExpress, it efficiently steps down higher DC voltages (such as 12V, 24V, or 36V power supplies) to lower regulated voltages (such as 5V or 3.3V) for microcontrollers, motors, and LED strips.

Operating at a 150 kHz150\text{ kHz} switching frequency, the LM2596 achieves power conversion efficiencies between 80% and 92%80\%\text{ and }92\%, generating significantly less heat than traditional linear regulators (like the LM7805 or LM317).

Quick reference

Regulator TypeMonolithic Step-Down (Buck) Switching Regulator
PackageTO-263 (D2PAK 5-Lead) / TO-220-5 / Blue Breakout Module
Input Voltage Range (VINV_{IN})4.5 V4.5\text{ V} to 40.0 V40.0\text{ V} DC (HV version up to 60V)
Output Voltage Range (VOUTV_{OUT})1.23 V1.23\text{ V} to 37.0 V37.0\text{ V} DC (Adjustable) / Fixed 3.3V, 5V, 12V
Continuous Output Current (IOUTI_{OUT})Up to 3.0 A3.0\text{ A} (with adequate copper PCB heatsinking)
Switching Frequency150 kHz150\text{ kHz} internal oscillator
Conversion Efficiency80%…92%80\% \dots 92\%
Control FeaturesON/OFF shutdown control pin (Low = ON, High = OFF)

Pinout (TO-263 5-Lead Package & Module Terminals)

text
        ┌──────────────────┐
        │   LM2596S-ADJ    │  (Front Package Face)
        └─┬───┬───┬───┬────┘
          1   2   3   4   5
         VIN SW  GND FB  ON/OFF
PinNameDescription
1VINUnregulated DC power input pin (+4.5 V to +40 V DC)
2OUTPUT / SWInternal NPN switch output (Connects to Schottky diode & 33µH inductor)
3GND / TABGround reference (0 V)
4FEEDBACK / FBVoltage feedback sensing pin (1.23V reference)
5ON/OFFLogic control input (Connect to GND for normal operation, High to shut down)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Input Voltage RangeVINV_{IN}4.512 / 2440VDC input
Output Feedback VoltsVFBV_{FB}1.1931.2301.267VAdjustable version
Continuous Load CurrentIOUTI_{OUT}—3.0—AVIN−VOUT≥3.0VV_{IN} - V_{OUT} \ge 3.0\text{V}
Current Limit ThresholdICLI_{CL}3.64.57.5AInternal switch peak current limit
Oscillator FrequencyfOSCf_{OSC}127150173kHzInternal switching clock
Quiescent CurrentIQI_Q—5.010.0mAOperating state (VFB=1.3VV_{FB} = 1.3\text{V})

Module Circuit & Voltage Calculation

text
       +V_IN (4.5V - 40V DC Input)
          │
       [Pin 1: VIN]
        LM2596S-ADJ ── [Pin 2: SW] ─── [ 33µH Inductor ] ───┬─── +V_OUT Regulated DC Output
          │                                  │              │
       [Pin 3: GND]               [SS34 Schottky Diode]  [ R1 = 1kΩ ]
          │                                  │              │
         GND ────────────────────────────────┴──────────────┼─── [Pin 4: FB]
                                                            │
                                                   [ R2 = Potentiometer ]
                                                            │
                                                           GND

VOUT=1.23V×(1+R2R1)V_{OUT} = 1.23\text{V} \times \left( 1 + \frac{R_2}{R_1} \right)

(Adjusting the brass screw on the 3296W multi-turn potentiometer changes R2R_2 to adjust output voltage).

Wiring (DC-DC Converter Module)

LM2596 Module Terminal→Power Source / LoadNotes
IN++VCC+V_{CC} (12V / 24V Power Supply)Positive input rail
IN-Power Supply GNDGround reference
OUT++VOUT+V_{OUT} (5V / 3.3V Load Rail)Regulated output voltage
OUT-Load GNDShared ground output
Warning

Adjusting Blue LM2596 Buck Modules for the First Time:

  • Blue LM2596 modules shipped from factories often have their multi-turn potentiometer preset to maximum voltage (VOUT=VINV_{OUT} = V_{IN}).
  • Turn the brass screw 10 to 15 full turns COUNTER-CLOCKWISE while measuring output with a multimeter to bring output voltage down to 5V before connecting sensitive microcontrollers.

Common mistakes

  • Attempting to step UP voltage: The LM2596 is a Buck (Step-Down) regulator. VINV_{IN} must be at least 1.5V1.5\text{V} higher than VOUTV_{OUT}. It cannot boost 5V5\text{V} up to 12V12\text{V} (use XL6009 or MT3608 for step-up boost).
  • Omitting external Schottky diode on custom PCBs: The LM2596 requires an external fast Schottky catch diode (e.g. 1N5822 or SS34) across the SW pin and GND to recirculate inductor current.

Notes

  • LM2596 vs XL4015 vs MP1584: LM2596 operates at 150kHz (3A max); XL4015 operates at 180kHz (5A max); MP1584 operates at 1.5MHz (tiny footprint).

Assets & downloads