Dual-Output (Positive and Negative), DC-DC Converter for CCD and LCD

The MAX685 DC-DC converter provides low-noise dual outputs for powering CCD imaging devices and LCDs. This device uses a single inductor to provide independently regulated positive and negative outputs. Integrated power switches are included in a small 24-Pin 4mm x 4mm Thin QFN package to save space and reduce cost. A 16-pin QSOP package is also available.

Each output delivers up to 10mA from a +2.7V to +5.5V input voltage range. Output voltages are set independently up to 24V and down to -9V. With a few additional low-cost components, the output voltages can be set at up to 45V and down to -16V. Output ripple magnitude is 30mVp-p. The MAX685 uses a fixed-frequency, pulse-width-modulated (PWM) control scheme at 220kHz or 400kHz to permit output noise filtering and to reduce the size of external components. The frequency can also be synchronized to an external clock signal between 200kHz and 480kHz.

The MAX685 has a power-OK indicator output (POK) that signals when both outputs are within regulation. A logic-controlled shutdown completely turns off both outputs and reduces supply current to 0.1µA. The user can also set which output turns on first.

The preassembled MAX685 evaluation kit is available to reduce design time.

Applications

* Camcorders * CCD Imaging Devices * Digital Cameras * LCDs * Notebook Computers

* Dual Output Using a Single Inductor

* Low-Noise Output, 30mVp-p Ripple

* Output Voltages up to 24V and down to -9V (up to 45V and down to -16V with added components)

* Internal Switches in a Small 24-Pin 4mm x 4mm Thin QFN Package

* 220kHz/400kHz Fixed-Frequency PWM Operation

* Frequency Can Be Synchronized to External Clock

* Power-OK Indicator

* Selectable Power-On Sequencing

* 0.1µA Logic-Controlled Shutdown