LM257652 kHz buck regulator
Switch, store and smooth: a lower DC voltage with less wasted heat.
LM2576 is a five-pin step-down switching regulator. This reference follows TI’s fixed 5 V versions in TO-220 and D²PAK packages; 3.3 V, 12 V, 15 V and adjustable versions are separate ordering options. An internal 52 kHz controller switches the input into an external inductor. A Schottky catch diode carries current while the switch is off, and the output capacitor smooths the filtered DC rail. The regulator can support up to 3 A with suitable external parts and cooling. Pin 2 is the switching node, pin 4 senses the filtered output, and pin 3 and the metal tab are ground.
DC inputSwitching outputGround & tabFeedback senseEnable / shutdown
LM2576TO-220-5Front view · leads down · pin 3 and tab are GND
LM2576D²PAK-5Top view · leads down · pin 3 and tab are GND
Click a lead or use the arrow keys. Front view · leads down · pin 3 and tab are GND
PIN 1 · DC input
Supply inputVIN
Function
Supplies the internal power switch, control circuit and bias current.
How to connect
Connect the positive DC supply and a short, local input bypass to ground.
Electrical note
The 5 V version is specified with 8–40 V input under its stated load conditions; 45 V is an absolute maximum, not an operating target.
PIN 2 · Switching output
Switch nodeSW
Function
Pulsed output of the internal high-side switch. This node drives the external inductor.
How to connect
Connect to the inductor input and Schottky cathode. The diode anode returns to GND.
Electrical note
This is not the filtered 5 V rail. Keep switch-node copper compact and away from feedback wiring.
PIN 3 · Ground & tab
Ground and metal tabGND
Function
Common return for the controller and power stage. The exposed metal tab is also ground.
How to connect
Connect to the input-capacitor return, catch-diode anode and output-capacitor return with short power paths.
Electrical note
On the SMD footprint, pin 3 and the thermal-pad sections have the same electrical pad number.
PIN 4 · Feedback sense
Output senseFB
Function
Senses the filtered output and closes the regulation loop. The fixed 5 V device includes its feedback divider internally.
How to connect
For the fixed 5 V example, connect directly to the output after the inductor, near COUT.
Electrical note
The adjustable variant instead needs an external divider referenced to approximately 1.23 V. Do not mix the two circuits.
PIN 5 · Enable / shutdown
Shutdown inputON/OFF
Function
Low enables switching; high shuts the regulator down.
How to connect
Connect to ground for an always-on converter.
Electrical note
Logic ON is guaranteed at 0.8 V or below and OFF at 2.4 V or above over the specified temperature range. The typical switching threshold is approximately 1.4 V.
At a glance
52 kHz buck regulator
Use an inductor, catch diode and suitable input/output capacitors. The filtered output—not the switch node—feeds the load and feedback pin.
5 V · fixed versionSelected output
52 kHz typicalSwitching frequency
−40–125 °CJunction operation
3 A · design-dependentOutput capability
Operating profile
LM2576T-5.0/NOPB
Choose the exact version
Key parameters and their test conditions
- Selected fixed output
- 5 VConditions / notes: LM2576T-5.0/NOPB and LM2576S-5.0/NOPB
- Other fixed outputs
- 3.3 V / 12 V / 15 VConditions / notes: Choose the matching suffix; changing a resistor does not reprogram a fixed version
- Adjustable option
- 1.23–37 V nominal rangeConditions / notes: ADJ version uses an external divider; input headroom is still needed
- HV version
- 60 V recommended supply ceilingConditions / notes: A separately ordered device; the selected non-HV parts remain limited to 40 V
- Straight TO-220 leads
- KC0005AConditions / notes: Do not substitute the footprint for LF02/LF03 formed-lead orderables
- Grounded tab
- Pin 3 electrical nodeConditions / notes: A heatsink or exposed pad can be electrically live at ground potential
Package details
Follows the selected physical package
- Manufacturer
- Texas Instruments
- Part number
- LM2576T-5.0/NOPB
- Package
- TO-220-5
- Connections
- 5 pins
- Mounting
- Through-hole
- Lead pitch
- 1.70 mm
- Package code
- KC
- Thermal reference
- Grounded tab; thermal performance depends on board copper and cooling
Connections by function
Select a pin to open its function, electrical notes and wiring guidance.
DC input1 pins
Switching output1 pins
Ground & tab1 pins
Feedback sense1 pins
Enable / shutdown1 pins
DC input1 pins
Switching output1 pins
Ground & tab1 pins
Feedback sense1 pins
Enable / shutdown1 pins
Switch ON: charge the inductor
The internal transistor connects VIN to pin 2. Inductor current rises while energy flows toward the load.
Switch OFF: keep current flowing
The catch diode conducts from ground into the switch node. Inductor current continues toward the load and falls gradually.
Close the control loop
Feedback senses the filtered output. The controller adjusts pulse width, while current limiting and thermal shutdown handle abnormal conditions.
The 12 V to 5 V, 1 A example has an ideal duty ratio of 41.7%. At 52 kHz and 100 µH, ideal inductor ripple is about 0.561 A peak-to-peak. These are calculated illustrations, not live measurements.
Pin reference
Select a pin to explore its function and connection.
5 pins
| Pin | Signal | Type | Function |
|---|---|---|---|
| VIN | Supply input | Supplies the internal power switch, control circuit and bias current. | |
| SW | Switch node | Pulsed output of the internal high-side switch. This node drives the external inductor. | |
| GND | Ground and metal tab | Common return for the controller and power stage. The exposed metal tab is also ground. | |
| FB | Output sense | Senses the filtered output and closes the regulation loop. The fixed 5 V device includes its feedback divider internally. | |
| ON/OFF | Shutdown input | Low enables switching; high shuts the regulator down. |
No pins match. Try a signal name or choose All pins.
Choose the exact version
Output and voltage class are ordering options
Manufacturer specifications 6 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Selected fixed output | 5 V | LM2576T-5.0/NOPB and LM2576S-5.0/NOPB |
| Other fixed outputs | 3.3 V / 12 V / 15 V | Choose the matching suffix; changing a resistor does not reprogram a fixed version |
| Adjustable option | 1.23–37 V nominal range | ADJ version uses an external divider; input headroom is still needed |
| HV version | 60 V recommended supply ceiling | A separately ordered device; the selected non-HV parts remain limited to 40 V |
| Straight TO-220 leads | KC0005A | Do not substitute the footprint for LF02/LF03 formed-lead orderables |
| Grounded tab | Pin 3 electrical node | A heatsink or exposed pad can be electrically live at ground potential |
No specifications match. Try a parameter name or a unit.
The package switch changes the physical package, not the regulator family or output-voltage suffix.
Operating envelope
Fixed 5 V option · TI SNVS107G
Manufacturer specifications 6 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Nominal output | 5 V | LM2576T-5.0 / LM2576S-5.0 |
| Specified input for 5 V regulation | 8–40 V | 0.5–3 A output load |
| Output at 25°C | 4.8–5.2 V | VIN = 8–40 V; ILOAD = 0.5–3 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 |
| Non-HV supply ceiling | 40 V maximum | The fixed 5 V regulation table uses 8–40 V input |
No specifications match. Try a parameter name or a unit.
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 specifications 6 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Oscillator | 52 kHz typical | 47–58 kHz at 25°C; 42–63 kHz over temperature |
| Switch saturation | 1.4 V typical | 3 A switch current; 1.8 V maximum at 25°C |
| Peak switch-current limit | 5.8 A typical | Protection threshold; not a continuous output rating |
| Shutdown threshold | 1.4 V typical | High = OFF; low = ON |
| Guaranteed enable / shutdown | ≤ 0.8 V / ≥ 2.4 V | Logic thresholds over specified temperature range |
| Standby supply current | 50 µA typical | ON/OFF = 5 V; 200 µA maximum under the stated test conditions |
No specifications match. Try a parameter name or a unit.
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 specifications 6 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Input / output | 12 V DC / 5 V DC | Fixed-output device; pin 4 connected directly to filtered output |
| Inductor L1 | 100 µH | Choose saturation/current ratings for load, ripple and current-limit behavior |
| Catch diode D1 | MBR360 · 3 A, 60 V Schottky | Cathode to pin 2; anode to GND; suitable for this 12 V illustration |
| Input CIN | 100 µF, 50 V | Low-ESR aluminum; check RMS ripple rating |
| Output COUT | 1000 µF, 25 V | Low-ESR aluminum; check TI ESR/stability guidance |
| Load | 5 Ω · at least 10 W | 1 A nominal; resistor dissipates 5 W |
No specifications match. Try a parameter name or a unit.
The inductor, diode and nominal capacitances follow TI’s fixed-output application. Input voltage and load here are a 12 V, 1 A teaching example. Validate startup, ripple, stability and thermal margins for the actual parts and conditions.
Understand the waveforms
Ideal continuous-conduction estimates
Manufacturer specifications 6 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Duty ratio | D ≈ 5 / 12 = 41.7% | Neglects switch and diode voltage drops |
| Switch period | 19.23 µs | 1 / 52 kHz |
| ON time | 8.01 µs | D / f |
| Inductor ripple | Approximately 0.561 A peak-to-peak | (12 − 5) × D / (100 µH × 52 kHz) |
| Peak current at 1 A average | Approximately 1.280 A | ILOAD + ΔIL/2 in ideal steady state |
| Output power | 5 W | 5 V × 1 A |
No specifications match. Try a parameter name or a unit.
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 specifications 6 parameters
| 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 | KC straight-lead pattern | 1.70 mm pitch; five holes in one row |
| D²PAK footprint | KTT five leads plus stepped thermal land | All pad-3 sections are GND |
No specifications match. Try a parameter name or a unit.
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 specifications 6 parameters
| 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 | 32.4°C/W | JEDEC four-layer board; real board and heatsinking change this value |
| TO-263 RθJA | 42.6°C/W | JEDEC four-layer board; depends strongly on copper and cooling |
No specifications match. Try a parameter name or a unit.
Thermal shutdown and current limiting provide protection; they do not replace a suitable board and cooling design.
Embedded DC rails
Create a lower-voltage rail from a higher DC supply when the input range, noise and load requirements suit the design.
Manufacturer application guidePower-stage learning
Explore the difference between switching-node pulses, inductor current and the filtered output.
Manufacturer application guideDistributed conversion
Place a buck stage near the load with short high-current loops and carefully routed feedback.
Manufacturer application guideTake it into ProTech
Find LM2576 in the Components Library to place its schematic symbol and connect its pins.
Reference page · circuit simulation model not yet availableOpen ProTech