DC2490A: 5V @ 840mA, 36 ~ 72 Vin

Demonstration circuit 2490A is a micropower no-optoisolated flyback converter featuring the LT®8303. This demo circuit outputs 5V, and maintains tight regulation with a load current from 2.5mA to 0.84A over an input voltage from 36V to 72V. The output current capability increases with the input voltage, as shown in the Performance Summary table.

The DC2490A needs less than 0.5% of its full output power as a minimum load to maintain good output voltage regulation. On the DC2490A, in order to avoid preloading, a 5.6V Zener diode is placed between its VOUT + and VOUT – to serve as a minimum load.

The Performance Summary table summarizes the performance of the demo board at room temperature. The demo circuit can be easily modified for different applications with some predesigned transformers.

The LT8303 is a micropower high voltage isolated flyback converter. By sampling the isolated output voltage directly from the primary-side flyback waveform, the part requires no third winding or opto-isolator for regulation. The output voltage is programmed with a single external resistor. Boundary mode operation provides a small magnetic solution with excellent load regulation. Low ripple Burst Mode® operation maintains high efficiency at light load while minimizing the output voltage ripple. A 0.45A, 150V DMOS power switch is integrated along with all the high voltage circuitry and control logic into a 5-lead ThinSOT™ package.

The LT8303 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with this quick start guide for demo circuit 2490A.