PFM controller boasts current 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 controller 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 controller permits a monotonic rising of the output voltage regardless of load condition. The efficiency of thedevice is rated up to 97 percent (typical) for a 400V input/12V output power supply.      

The 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).      

Fairchild’s FAN7688 advanced PFM controller is available in a 16-pin, SOP package, has a wide operating frequency spanning 36–690 KHz, and works over a temperature range from ‑40 to +125 degrees Celsius.

The controller is ideally suited 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.