3 A buck regulator with a 4 V to 40 V input window
The LM2576SX-5.0/NOPB is a fixed 5 V output step-down (buck) regulator from Texas Instruments' SIMPLE SWITCHER series, delivering up to 3 A continuous output. The 52 kHz switching frequency is low enough to keep inductor losses modest but high enough to keep the magnetics under 10 mm height in most designs.
What the 52 kHz switching frequency means for your BOM
At 52 kHz, the LM2576SX-5.0/NOPB operates well below the AM broadcast band and avoids the EMI headaches of 200 kHz+ switchers. The trade-off is a larger inductor — typically a 100 µH to 330 µH shielded drum core — than a 500 kHz part would need. For a 3 A rail, that inductor sits around 12 mm × 12 mm, which is manageable on a TO-263-based layout. The fixed switching frequency also means the output ripple is predictable: about 50 mVpp with a 220 µF electrolytic at the output, assuming the inductor current ripple stays within 30 % of the load.
Package and thermal: the DDPAK tab is your heat path
The LM2576SX-5.0/NOPB comes in a TO-263-5 (DDPAK) surface-mount package with an exposed tab on the bottom. Without a proper thermal pad, the junction temperature will exceed the 125 °C limit at 3 A output with 12 V input. The package footprint is the same as the through-hole TO-220 version (LM2576T-5.0), so a board designed for the TO-220 can be adapted with a pad pattern change.
The NOPB suffix indicates lead-free (RoHS) plating on the leads, which is the standard for new builds.