NCP346SN1EVB ON Semiconductor

xxxAYW NCP346 Overvoltage Protection IC The NCP346 Overvoltage Protection circuit (OVP) protects sensitive electronic circuitry from overvoltage transients and power supply faults when used in conjunction with an external Pchannel FET. The device is designed to sense an overvoltage condition and quickly disconnect the input voltage supply from the load before any NCP346 V CC (5) IN (4) V CC V5 Preregulator R1 OUT V CC (1) + LOGIC ON/OFF OUT COMP BLOCK DRIVER R2 Bandgap Reference CNTRL (3) GND (2) Figure 2. Detailed Block Diagram PIN FUNCTION DESCRIPTIONS Pin Symbol Pin Description 1 OUT This signal drives the gate of a Pchannel MOSFET. It is controlled by the voltage level on IN or the logic state of the CNTRL input. When an overvoltage event is detected, the OUT pin is driven to within 1.0 V of V in less CC than 1.0 sec provided that gate and stray capacitance is less than 12 nF. 2 GND Circuit Ground 3 CNTRL This logic signal is used to control the state of OUT and turnon/off the Pchannel MOSFET. A logic High results in the OUT signal being driven to within 1.0 V of V which disconnects the FET. The input is tied Low via an CC internal 50 k pulldown resistor. It is recommended that the input be connected to GND if it is not used. 4 IN This pin senses an external voltage point. If the voltage on this input rises above the overvoltage threshold (V ), th the OUT pin will be driven to within 1.0 V of V , thus disconnecting the FET. The nominal threshold level can be CC increased with the addition of an external resistor divider between IN, V , and GND. CC 5 V Positive Voltage supply. OUT is guaranteed to be in low state (MOSFET ON) as long as V remains above CC CC 2.5 V, and below the overvoltage threshold. TRUTH TABLE IN CNTRL OUT <V L GND th <V H V th CC >V L V th CC >V H V th CC