Typical Application


Ø   Constant-Current (CC) and Constant-Voltage (CV) with Primary Side Control

Ø   Proprietary technology enabling high efficiency and fast dynamic response

Ø   No audible noise over entire operating range

Ø   Applications from 1W to more than 18W output

Ø   Direct drive of BJT or MOS switch

Ø   Built-in Cable Compensation

Ø   Built-in Line Compensation

Ø   Primary-side feedback eliminates opto-coupler and TL431

Ø   Cycle-by-Cycle Current Limiting

Ø   Over Temperature Protection

Ø   VCC Over Voltage Protection

Ø   Open Circuit Protection


The FT839Dx controller device is optimized for high-performance, low power switching mode power supply applications. The FT839Dx facilitates CC/CV charger design by eliminating an opto-coupler and TL431. Its highly integrated functions such as Under Voltage Lockout (UVLO), Leading Edge Blanking (LEB) and built-in cable compensation offer the users a high efficiency and low cost solution for AC/DC power applications.  

Power supplies built with FT839Dx can achieve both highest average efficiency and fast dynamic load response.

Furthermore, FT839Dx features fruitful protections like Open Circuit Protection and Over Temperature Protection to eliminate the external protection circuits and provide reliable operations. FT839Dx is available in SOT23-5 package.


Ø   Adapter/Charger for Cell/Cordless Phones,PDAs, MP3 and Other Portable Apparatus

Ø   Standby and Auxiliary Power SuppliesSet Top Boxes (STB)

Ø   AC/DC LED Driver applications