3A adjustable buck regulator — what it does
The LM2596S-ADJ is a SIMPLE SWITCHER® step-down buck regulator from Texas Instruments, delivering up to 3A output from an input range of 4.5V to 40V. The adjustable output version lets you set Vout from 1.2V up to 37V with two external resistors. Switching frequency is fixed at 150 kHz, which keeps the inductor and capacitor sizes reasonable but means the part is not a candidate for noise-sensitive RF or audio rails — the ripple fundamental lands at 150 kHz plus harmonics.
Sizing the input and output rails
Minimum input is 4.5V, so a 5V rail with 5% tolerance is workable; the 40V max input covers 24V industrial supplies and 36V nominal telecom buses with margin. Output voltage is adjustable from 1.2V to 37V — the upper limit is Vout(max) = Vin - dropout, so a 40V rail can regulate down to 37V but not to 38V. The 3A current rating is continuous, not peak.
The adjustable version is no longer factory-supported.