The LT1424-5 is a monolithic high power switching regulator specifically designed for the isolated flyback topology. No “third winding” or optoisolator is required; the integrated circuit senses the isolated output voltage directly from the primary side flyback waveform. A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry. The LT1424-5 operates with input supply voltages from 3V to 20V and draws only 7mA quiescent current. It can deliver up to 400mA at 5V with no external power devices. By utilizing current mode switching techniques, it provides excellent AC and DC line regulation. The LT1424-5 has a number of features not found on other switching regulator ICs. Its unique control circuitry can maintain regulation well into discontinuous mode. Load compensation circuitry allows for improved load regulation. An externally activated shutdown mode reduces total supply current to 20µA typical for standby operation.
The LT1424-5 is a monolithic high‑power isolated flyback switching regulator designed for 1:1 ratio transformers. It provides a fixed 5 V output, operates from 3 V to 20 V input, and delivers up to 400 mA with a quiescent current of only 7 mA. The device includes load compensation and a shutdown mode that reduces supply current to a few tens of microamperes.
The document contains absolute maximum ratings, electrical characteristics, typical performance curves, pin descriptions, block and timing diagrams, operation theory, package dimensions, and a typical application circuit. It is intended for designers of isolated power supplies and industrial automation equipment.
| Input Supply Voltage Range | 3 V to 20 V |
|---|---|
| Quiescent Supply Current | 7 mA |
| Output Current (5 V) | up to 400 mA |
| Switching Frequency (typical) | 285 kHz |
| Shutdown Mode Supply Current | 15 pA to 40 pA |
| Operating Temperature Range (industrial) | -40 °C to 125 °C |
The SHDN pin shuts down the regulator and reduces the input current to a few tens of microamperes.
A common 0.1 pF ceramic capacitor is sufficient for the RECOMP pin.
The device operates with input voltages from 3 V up to 20 V.
The typical switching frequency is 285 kHz.