Boost and flyback workhorse in a TO-220-5
The Texas Instruments LM2577T-ADJ/LF03 is a SIMPLE SWITCHER® monolithic IC that integrates a 3 A NPN switch into a boost, flyback, or forward-converter topology. It accepts a 3.5 V to 40 V input and delivers an adjustable output from 1.23 V up to 60 V (switch rating). The 52 kHz fixed-frequency oscillator keeps the LC filter components small enough to fit on a single-sided PCB — a practical choice for motor-drive bias rails, industrial control auxiliary supplies, and telecom line cards where through-hole assembly is preferred.
52 kHz switching — inductor sizing trade-off
At 52 kHz the switching period is about 19 µs, which lets you use a standard drum-core or toroid inductor in the 47 µH to 330 µH range for most boost designs. The same frequency keeps the diode recovery-loss manageable with a Schottky — a 3 A, 60 V Schottky like the MBR360 handles the catch-diode duty without a heatsink in most TO-220 layouts. The trade-off is output ripple amplitude; plan for 50 mV to 100 mV p-p at full load unless you add a second LC stage.
3 A switch — where the output power ceiling lands
In a typical boost from 5 V to 12 V, that translates to roughly 15 W output before the current-limit foldback engages. For flyback applications the usable power is lower — the transformer turns ratio and leakage inductance eat into the switch duty-cycle budget. The part has no synchronous rectifier, so the Schottky catch diode carries the full output current during the switch-off interval; diode selection directly affects efficiency, especially at low input voltages where the duty cycle is high.
Through-hole assembly — rework and field-service angle
The TO-220-5 package with formed leads is a standard through-hole footprint that fits the same 0.100-inch pitch as the original LM2577T-ADJ. The formed leads let the body sit flush against the PCB or a heatsink — the tab is the switch collector, so a thermal pad or a clip-on heatsink is advisable above 10 W dissipation. The leads are tin-plated and compatible with leaded solder profiles; no special bake-out or moisture sensitivity level applies.
That means Texas Instruments is still manufacturing the die and assembling the TO-220 package — no last-time-buy notice, no end-of-life window to manage.
Sourcing — quoted to order per BOM quantity
No minimum order threshold beyond the standard tube quantity.