Circuit using MAX1578 to drive high-power white LED

　This circuit includes a charge pump regulator ( IC 1) suitable for camera flash applications. This device can provide current regulation function for up to 8 white LEDs . Connecting LED1 to LED8 in parallel can provide a current of up to 480mA for a single 1W LVXEONStar high-power white LED module. When the potential of the open-drain input pin EN is pulled down to ground, IC1 enters shutdown mode. A compact and low-cost thermal shutdown circuit can be constructed using a thermistor and a dual open-drain comparator ( IC 2) with an internal reference. When VTHERM drops below the 1.2V internal reference voltage, internal comparator A pulls the EN pin potential down to ground. This operation is performed when the temperature of the thermistor (R2) is very high. The internal comparator B is used to provide open circuit fail protection, that is, when the thermistor contact is open, the EN pin potential will be pulled low. When an open-circuit fault occurs in the thermistor, VTHERM is pulled high by R1, causing comparator B to pull the EN pin potential low. Resistor dividers R3 and R4 are used to set the threshold voltage for open circuit faults, and resistor R1 and thermistor R2 are used to set the thermal shutdown threshold. When the temperature is too high and the thermistor has an open or short circuit failure, the white LED will be turned off.