Miniature Isolated Solution Using LT8301 and Coupled Inductor

Customers that require miniature solutions with only functional isolation often choose isolated modules. These solutions have very bulky form factors, and typically do not provide high power efficiency or a low no-load input current. In addition, the output voltages of these modules are usually unregulated, having large VOUT variations due to line/load changes. But now, the LT8301, a simple-to-use no-opto isolated flyback converter can provide such customers a much more compact high-performance solution, using coupled inductors. With the micropower LT8301, high power efficiency and low no-load input current can be achieved. Meanwhile, the output voltage can be simply set by a resistor, and tightly regulated to the target value over a wide range of input voltage and load current.

Figure 1. Miniature 5V isolated flyback converter using a coupled inductor.

The schematic in Figure 1 shows a miniature 5V isolated flyback converter using the LT8301, with a coupled inductor, L1, to provide functional isolation. The entire solution requires very few components, and the total size is about 13mm × 7mm × 3mm. The 5V output voltage is tightly regulated over a 2.7V to 16V input voltage range, with a peak power efficiency of 85%. To meet the 1mA minimum load requirement, a 5kΩ resistor should be added at VOUT, or a Zener diode should be used to clamp VOUT. In the case of VOUT being clamped by a 5.6V Zener diode, the no-load input current remains below 2mA over the entire input voltage range.

Figure 2. LT8301 Efficiency and Load/Line Regulation.



Bryan Legates


Chen Zheng