Ground Fault Interupter

The FAN4147 is a low-power Ground Fault Interrupter (GFI) controller for detecting hazardous current paths to ground and ground-to-neutral faults. The FAN4147 application circuit opens the load contacts before a harmful shock occurs. Internally, the FAN4147 contains a diode rectifier, precision bandgap 12V shunt regulator, precision low-VOS offset-sense amplifier, time delay noise filter, window-detection comparators, and an SCR driver. With a minimum number of external components, the FAN4147 detects and protects against a hot-wire-to-ground fault and a neutral-line-to-neutral-load short. The minimal components and the small SuperSOT™ package allow for a small-form-factor, low-cost solution. The FAN4147 circuitry has a built-in rectifier and shunt regulator that operates with a low quiescent current. This allows for a high-value, low-wattage-series supply resistor. The internal temperature-compensated shunt regulator, sense amplifier, and bias circuitry provide for precision ground-fault detection. The low-VOS offset-sense amplifier allows direct coupling of the sense coil to the amplifier’s feedback signal. This eliminates the large 50/60Hz AC-coupling capacitor. The internal delay filter rejects high-frequency noise spikes common with inductive loads. This decreases false nuisance tripping. The internal SCR driver is temperature compensated and designed to satisfy the current requirements for a wide selection of external SCRs. The minimum number of external components and the 6-pin SuperSOT™ package enable a low-cost, compact design and layout.