DC1825A

LINEAR TECHNOLOGY DC1825A Evaluation Board, Flyback Converter, Load Current of 1mA to 250mA, 2V-75V Input, 5V Output

The demonstration board is an isolated flyback converter featuring LT8300ES5 device. The LT8300ES5 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 optoisolator for regulation. The output voltage is programmed with a single external resistor. Internal compensation and soft start further reduce external component count. This demo board outputs 5.0V and maintains tight regulation with a load current from 1mA to 250mA and over an input from 22V to 75V, with a nominal 48V. The output current capability increases with the input voltage. The DC1825A needs a very small minimum load to regulate the output voltage. The standby input current of the demo circuit is less than 400µA typical because of the low quiescent current design of the IC and very small minimum load requirement.

.

Typical switching frequency of 330KHz

.

Minimum switching frequency of 8KHz

.

80% efficiency

.

Boundary mode operation at heavy load

.

Low ripple burst mode operation at light load

.

Minimum load is less than 0.5% typ of full output

.

VOUT set with a single external resistor

.

No transformer third winding or optoisolator required for regulation

.

Accurate EN/UVLO threshold and hysteresis

.

Internal compensation and soft start

The LT8300 requires very small minimum load to maintain good output voltage regulation. A zener diode is placed on the output to clamp the voltage to 5.0V.