An LM2576-ADJ makes a variable DC buck supply by switching a higher DC input down to a regulated output. Set the output with a two-resistor feedback divider, then select the inductor, diode, capacitors and thermal design for the actual input voltage and load. The standard LM2576 supports up to 40 V input and an adjustable output specified from 1.23 V to 37 V; the LM2576HV raises the input limit to 60 V and the adjustable-output specification to 57 V. Neither version can boost voltage above its input.
What the LM2576 adjustable supply does
The LM2576 is a monolithic step-down (buck) switching regulator. It switches current through an inductor and uses feedback to hold the output near a set voltage as input or load conditions change. TI rates the family to drive a 3 A load; that is a device capability, not a guarantee that every circuit will deliver 3 A under every voltage and cooling condition. Fixed-output and adjustable-output versions are available. The LM2576-ADJ is the relevant version when the output must be set with external resistors.
A buck converter only steps voltage down. The input must be high enough above the desired output to accommodate the regulator’s operating limits and losses. The nominal output range alone does not establish that a chosen input, load and temperature combination will work; check the datasheet’s electrical limits and test the completed circuit.
Choose standard LM2576 or LM2576HV
| Variant | Maximum input voltage | Adjustable output specification | What to check |
|---|---|---|---|
| LM2576-ADJ | 40 V maximum input (TI datasheet) | 1.23 V to 37 V (TI specification) | Usable output depends on input headroom, duty cycle, load and thermal conditions. |
| LM2576HV-ADJ | 60 V maximum input (TI datasheet) | Up to 57 V (TI specification) | Usable output remains limited by input voltage, headroom, duty cycle, load and temperature. |
These are separate voltage ratings, not permission to operate at the maximum input while expecting the maximum output. Choose the version based on the highest possible supply input, including variation or transients, and verify that the resulting input-to-output difference and load fit the datasheet. A buck regulator cannot produce an output higher than its input.
#1 Best Overall
- LM2576T-ADJ is an adjustable 3A switching regulator for flexible power designs
- Flexible power designs requiring adjustable voltage with higher current benefit from its design
- Good current capability with adjustable output provide design flexibility
- Adjustable output with 3A capability allows for various application requirements
- Flexible power supplies variable voltage systems and adjustable applications
How to set the output voltage
The adjustable version compares the feedback-pin voltage with an internal reference of approximately 1.23 V. A resistor divider from the output to ground feeds that pin. If Rtop connects output to feedback and Rbottom connects feedback to ground, the nominal relationship is:
Vout ≈ 1.23 V × (1 + Rtop / Rbottom)
For a target output, choose the lower resistor first and calculate the upper resistor as Rtop ≈ Rbottom × (Vout/1.23 − 1). This ideal calculation does not account for reference tolerance, resistor tolerance, wiring effects or the converter’s operating limits, so measure the assembled supply under load.
Rank #2
- Product Type: Adjustable Step-Down Voltage Regulator Transistor
- Model Specification: The model number is LM2576T-ADJ and it is enclosed in a TO-220-5 package.
- Functionality: This transistor does not belong to NPN/PNP, NMOS/PMOS, Darlington, JFET, or IGBT types.
- Application: Primarily used for voltage regulation, step-down functions, and current control in various electronic circuits.
- Packaging: Comes in a pack of 10 units, ensuring adequate supply for your projects. Delivered in an Anti-Static bag for electrostatic protection and a prolonged shelf life.
TI’s LM2576/LM2576HV datasheet Rev. G, revised March 2023, illustrates a “1.2-V to 55-V Adjustable 3-A Power Supply With Low Output Ripple” using 50-kΩ and 1.21-kΩ feedback resistors. That is a datasheet example, not a universal bill of materials or a promise that any build will cover that full range. Use the recommended circuit and component guidance for the exact variant and conditions.
External parts and selection checks
The regulator IC is only one part of the converter. The inductor stores and releases energy during switching; the catch diode carries inductor current while the internal switch is off; capacitors manage input and output ripple; and the divider sets the output. TI’s illustrated HV circuit uses a 150-µH inductor, 1N5822 diode, 100-µF input capacitor, 2000-µF output capacitor, and 50-kΩ/1.21-kΩ feedback resistors. Treat these as values from that specific application circuit, not as universal selections for every input, output and load.
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Rank #3
- LM2576T-12 is a 12V 3A switching regulator for higher current power applications
- Higher current power applications requiring 12V regulation benefit from its 3A capability
- Good current handling with efficient switching ensures reliable power delivery
- Higher current rating makes it suitable for more demanding power applications
- Higher current power supplies 12V systems and power applications
- Inductor: Select inductance and current capability using TI’s recommendations for the intended input/output conditions. Its saturation-current rating must exceed the peak inductor current; saturation can cause excessive current and heating.
- Catch diode: Use a suitably rated fast Schottky diode where called for by the design. Orient it with its anode at ground and cathode at the switching node, as shown in TI’s buck circuit. Check reverse-voltage and forward-current ratings against the circuit conditions.
- Input capacitor: Place a capacitor across the regulator input and ground with a voltage rating safely above the maximum input. Check ripple-current capability as well as capacitance and temperature rating.
- Output capacitor: Choose capacitance, voltage rating and ripple-current capability for the desired output and load. The example’s 2000-µF value reflects its circuit and should not be copied without checking the datasheet’s stability and ripple guidance.
- Feedback resistors: Use the calculated ratio for the desired nominal output and account for resistor tolerances. Keep the feedback connection away from noisy switching paths.
Layout, heat and protection
Keep the high-current switching loop—input capacitor, internal switch, catch diode and return—short and compact to reduce parasitic inductance and noise. Follow TI’s pinout and layout guidance, use suitable copper and grounding, and route feedback from the output node without coupling it to the switching node. Poor layout can undermine ripple and regulation even when the schematic is correct.
Check dissipation at the expected input, output and load conditions, then provide adequate board copper or heatsinking as required by the package and thermal environment. The LM2576 includes cycle-by-cycle current limiting and thermal shutdown, and its ON/OFF pin provides shutdown control. Those features help protect the device under faults; they do not replace correctly rated components, good layout, cooling or load testing.
Rank #4
- Input: DC3V-40V DC or AC 2~30V
- Output: 3~40V DC linear adjustable
- Power: 15 Watt max
- Current: 1.5A, 2.5A peak (need a bigger heat sink for higher current output)
Efficiency and practical validation
TI’s Rev. G datasheet reports a 77% minimum-efficiency test point for 12-V input, 5-V output and 3-A load in its specified test circuit. This is a result under that stated datasheet condition, not a general efficiency figure for other voltage ratios, loads, layouts or builds. In a finished supply, verify output voltage and ripple across the intended input and load range, check component and regulator temperatures, and confirm startup and shutdown behavior before connecting sensitive equipment.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When this design is a good fit
An LM2576-ADJ circuit is useful when a straightforward adjustable buck supply is needed and the switching regulator’s voltage and thermal limits suit the application. Its architecture requires an external inductor, diode and capacitors, plus divider resistors. Newer synchronous converters may differ in switching frequency, efficiency, external-part count and thermal behavior, but no universal advantage can be inferred without comparing specific parts under the same test conditions. Also confirm present-day availability of the exact LM2576 package and suffix before designing around it.
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Best Value
- Features: Built with SANYO solid capacitors, 36μ thick PCB, high-Q inductors, and an LED output indicator for enhanced performance and reliability
- Application: Perfect for DIY power bank projects, powering monitors, communication devices, and a wide range of other electronic equipment
- Wide Input Voltage Range: The LM2596 buck converter supports a broad input voltage range from 3V to 40V, making it ideal for various applications, including DIY electronics, solar power systems, and more.(Input voltage must be at least 1.5V higher than the output voltage; no boost function)
- High-Efficiency Output: Achieve up to 92% conversion efficiency with this step-down regulator, ensuring stable and efficient voltage regulation for your devices, from 1.25V to 35V
- Adjustable Voltage Regulator: Easily customize the output voltage with a precision multi-turn potentiometer, providing flexibility for powering a wide range of electronic projects and devices
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