3A fixed 3.3V buck — the workhorse regulator for 12V/24V rails
The Texas Instruments LM2596T-3.3 is a SIMPLE SWITCHER® step-down regulator delivering a fixed 3.3V output at up to 3A from input voltages between 4.5V and 40V. It uses a 150 kHz switching frequency — a deliberate choice that keeps the inductor small and the EMI profile predictable, at the cost of slightly larger output ripple than a modern 500 kHz part. The TO-220-5 package with formed leads suits through-hole assembly and can be bolted to a heatsink for higher current draws.
150 kHz switching — inductor sizing and ripple trade-off
At 150 kHz, the LM2596T-3.3 requires a 33 µH to 47 µH inductor for typical 3A designs — larger than what a 500 kHz part would need, but the lower frequency reduces core losses and keeps the switch-node ringing manageable without snubbers. The fixed 3.3V output means no external feedback divider; the internal reference and error amplifier set the regulation point.
The TO-220-5 package has a metal tab on the back side that connects to the output pin — in a through-hole layout, the tab can be soldered to a copper pour or bolted to a chassis heatsink. Without a heatsink, the 3A output is limited to about 2A at 85°C ambient; with a modest clip-on heatsink, the full 3A is available across the temperature range.
For through-hole designs, the LM2596T-ADJ (adjustable output) can be set to 3.3V with two resistors, but the BOM adds two components and the feedback node is more noise-sensitive.