Step-Up Converters – for LCD and OLED display bias

Maxim introduced the MAX8570-MAX8575 family of high-efficiency, step-up converters for LCD and OLED display bias used in personal digital assistants (PDA), digital still cameras (DSC), mobile phones, palmtop computers, and other handheld portable equipment. The converters operate from a 2.7V to 5.5V supply voltage and have an internal switch that delivers up to 28V at the output.

The MAX857x family offers up to 87% efficiency and only 25&#181A quiescent current in light-load conditions. Each device includes an extra internal switch to provide true shutdown, completely disconnecting the output from the input supply when the device is not active. The MAX857x converters address the long-standing problem of display damage resulting from runaway output for high-voltage boost converters.

Protection features make these ICs extremely robust. For example, if the output capacitor or one of the feedback resistors is disconnected or missing, the devices protect the internal switch from being damaged. In fact, in response to most fault conditions, the MAX8570 family protects not only itself but also the downstream circuitry.

The MAX8570 family is offered with 110mA, 250mA, and 500mA current limits in both adjustable and fixed output voltages. This allows designers to select the best device to minimize output ripple and component size, and maximize efficiency for their specific application.

The MAX857x family is specified for the extended temperature range (-40&#176C to +85&#176C) and packaged in a 6-pin SOT23. Evaluation kits are available with recommended external components to speed designs. Prices start at $1.25 (1000-up, FOB USA).

Maxim Integrated Products Ltd , Theale, Berks RG7 4XX, UK.

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