3 A, 150 kHz — the workhorse buck that does not need a lab bench
The LM2596S-ADJ/NOPB: It is a non-synchronous buck with a fixed 150 kHz oscillator — no external compensation, no complicated loop tuning. The adjustable output version lets you set Vout anywhere from 1.2 V up to 37 V with two feedback resistors. This is the part you keep in the field kit because it swaps in without a scope: the TO-263-5 package has a big tab that sinks heat into the board copper, and the pinout is standard enough that you can usually read the silkscreen and get it right the first time.
Input range and thermal — what the ratings mean on a real board
The 4.5 V minimum input means it will start from a 5 V rail with some headroom, but not from a single-cell Li-ion. The 40 V maximum covers 24 V industrial supplies with margin for transients. At 3 A and 150 kHz, the inductor ripple current is around 30 % of load — a 33 µH to 47 µH shielded inductor handles it cleanly. No synchronous rectifier means the external Schottky diode takes the hit on efficiency at light load, but it also means the part is dead simple to troubleshoot with a multimeter.
No last-time-buy notice, no end-of-life window. The NOPB suffix confirms lead-free (RoHS) plating on the DDPAK/TO-263-5 tab and leads.