A Power Management Interface Circuit For Telecom Hot Swap With Local Dc/dc Conve


Posted on Feb 6, 2014

New cellular phones have incorporated high resolution cameras, which require high brightness illumination of the ambient area in order to achieve high quality pictures. Traditional xenon-filled photo Flash cannot be used in the very tight space available to photo cameras in cellular phones. Instead, design engineers use a white LED with high pulse


A Power Management Interface Circuit For Telecom Hot Swap With Local Dc/dc Conve
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d current. It occupies small PCB space when compared with a traditional photo Flash however, it also provides significantly lower light. Additionally, this high current CAN overload the phone battery during Flash A possible solution to this problem is to use two or three LEDs instead of one in order to improve the light output and use a super capacitor to avoid battery overload. An example of this solution is shown below in Figures 1 and 2. The circuit uses three SP7618 LED Driver ICs with one photo Flash LED connected to each driver and 0. 5F super capacitor that acts as an energy storage element during the Flash pulse. DESCRIPTION AND BOARD SCHEMATIC The SP7618 is a linear low-side constant-current driver designed to drive high power LEDs from an input voltage rail. The driver acts as a high current source, ensuring constant LED current for the full range of input voltage. The SP7618 allows implementing the lowest cost LED Driver for a variety of applications. Internal circuitry maintains the preset constant current output for a wide voltage range at the LED input. The LED current CAN be adjusted up to 1033mA with an external Clock applied to the CTRL pin. Dimming CAN be achieved by using the sequencing CTRL pin or feeding a PWM signal to the EN pin. The built-in thermal protection automatically stops LED current to prevent overheating. A timeout function serves as a fail safe, shutting down the output for currents...




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