Digital Camera Step-Down Power Supply

The MAX1802 provides a complete power-supply solution for digital still cameras and video cameras by integrating two high-efficiency step-down DC-DC converters and three auxiliary step-up controllers. This complete solution is targeted for applications that use either three to four alkaline cells or two lithium-ion (Li+) cells.

The main step-down DC-DC controller accepts inputs from 2.5V to 11V and regulates a resistor-adjustable output from 2.7V to 5.5V. It uses a synchronous rectifier to regulate the output with up to 94% efficiency. An adjustable operating frequency (up to 1MHz) facilitates designs for optimum size, cost, and efficiency.

The core step-down DC-DC converter accepts inputs from 2.7V to 5.5V and regulates a resistor-adjustable output from 1.25V to 5.5V. It delivers 500mA with up to 94% efficiency.

The three auxiliary step-up controllers can be used to power the digital camera's CCD, LCD, and backlight. The MAX1802 also features expandability by supplying power, an oscillator signal, and a reference to the MAX1801, a low-cost slave DC-DC controller that supports step-up, single-ended primary inductance converter (SEPIC), and fly-back configurations.

The MAX1802 is available in a space-saving 32-pin TQFP package (5mm x 5mm body), and the MAX1801 is available in an 8-pin SOT-23 package. An evaluation kit (MAX1802EVKIT) featuring both devices is available to expedite designs.

Applications

* Digital Still Cameras * Digital Video Cameras * DVD Players * Handheld Devices * Internet Access Tablets * PDAs

* 2.5V to 11V Input Voltage Range

* Main DC-DC Controller

* 94% Efficiency

* +2.7V to +5.5V Adjustable Output Voltage

* Up to 100% Duty Cycle

* Independent Shutdown

* Core DC-DC Converter

* 94% Efficiency

* Up to 500mA Load Efficiency

* Output Voltage Adjustable Down to 1.25V

* Independent Shutdown

* Three Auxiliary DC-DC Controllers

* Adjustable Maximum Duty Cycle

* Independent Shutdown

* Power, Oscillator, and Reference Outputs to Drive External Slave Controllers (MAX1801)

* Up to 1MHz Switching Frequency

* 3µA Supply Current in Shutdown Mode

* Internal Soft-Start

* Overload Protection for All DC-DC Converters

* Compact 32-Pin TQFP Package