15V fixed-output buck regulator at 3A — the SIMPLE SWITCHER® workhorse
The Texas Instruments LM2576SX-15 is a fixed 15V output step-down (buck) regulator from the SIMPLE SWITCHER® family, delivering up to 3A continuous output current. It operates at a fixed 52 kHz switching frequency, which simplifies inductor selection and keeps the LC filter components relatively large but predictable. The input voltage range spans 4V to 40V, making it suitable for unregulated DC rails from multi-cell battery stacks, 12V or 24V industrial supplies, and automotive systems after transient protection.
52 kHz switching — inductor sizing and output ripple trade-off
The fixed 52 kHz switching frequency is low by modern standards. It means the inductor value will be in the 100 µH to 330 µH range for a 15V output at 3A, and the output voltage ripple will be higher than a 100 kHz+ regulator. The trade-off is lower switching losses and simpler EMI filtering — the fundamental and its harmonics sit well below the AM broadcast band. No synchronous rectifier is used internally (the part uses an external Schottky catch diode), so the efficiency peaks around 75-80% depending on the input voltage and load. The diode selection is critical: a 3A, 45V Schottky with a low forward voltage keeps the dissipation manageable.
For new designs or BOM lines that need a guaranteed supply, the closest functional replacement within the SIMPLE SWITCHER® family is the LM2576HVSX-15 (higher input voltage version, also obsolete) or a more modern pin-compatible alternative such as the LM2596 series, which operates at 150 kHz and offers higher efficiency. Verify pin compatibility and output voltage tolerance before substituting.
The wide temperature range also covers cold-crank conditions in automotive 12V systems.