First LLC controller with current-mode control and synchronous rectification

Mouser is now stocking the Fairchild Semiconductor FAN7688 advanced pulse frequency modulated (PFM) controller. Integrating an advanced two-inductor, one capacitor (LLC) resonant controller with current-mode control and synchronous rectification (SR), the FAN7688 is one of the industry's first isolated DC-DC controller chips that adds charge current control to LLC resonant power supply units (PSUs) versus traditional voltage-mode control. The robust features and high efficiency of the FAN7688 enables designers to improve the reliability and efficiency of their power supplies for a variety of uses, including servers, telecoms, PC, industrial, and TV applications. The FAN7688 employs Fairchild's charge-current control technology, enabling the controller to use current-mode control opposed to voltage mode control. Using a triangular waveform, the oscillator on the FAN7688 is combined with the integrated switch current information to determine switching frequency. This advanced technique offers better control-to-output transfer functionality of the power stage, which not only helps simplify the feedback loop design, but also allows true input power limit capabilities. A closed-loop soft-start on the FAN7688 permits a monotonic rising of the output voltage regardless of load condition. The efficiency of the FAN7688 is rated up to 97 percent (typical) for a 400V input/12V output power supply. The FAN7688 controller's comprehensive set of protection functions also help in providing its best-in-class efficiency when it comes to isolated DC/DC converters. These features include over-load protection (OLP), over-current protection (OCP), output-short protection (OSP), over-voltage protection (OVP), over-temperature protection (OTP), and NON zero-voltage switching prevention (NZS). The device is available in a 16-pin SOP package, has a wide operating frequency spanning 36-690kHz, and works over a temperature range from 40C to +125C. The controller is ideal for a variety of applications, including desktop servers, telecom power supplies, intelligent off-line power supplies, high-efficiency DC/DC converters, industrial power and large screen display power. In addition, the FAN7688 is supported by two evaluation boards, the FEBFAN7688_I00250A and the FEBFAN7688SJXA_CP14U306, also available from Mouser stock.