Simplified Block Diagram
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- Drives Backplane and Backlight
- 4V to 30V Battery Voltage Range
- Low 500µA Supply Current
- Digital or Potentiometer Control of CCFL Brightness and LCD Bias Voltage
- Negative LCD Contrast (MAX753)
- Positive LCD Contrast (MAX754)
- Independent Shutdown of Backlight and Backplane Sections
- 25µA Shutdown Supply Current
- Notebook Computers
- Palmtop Computers
- PDAs and Other Handheld Devices
- Pen-Based Data Systems
- Portable Data-Collection Terminals
Both the backplane bias and the CCFL supply can be shut down independently. When both sections are shut down, supply current drops to 25µA. The LCD contrast and CCFL brightness can be adjusted by clocking separate digital inputs or using external potentiometers. LCD contrast and backlight brightness settings are preserved in their respective counters while in shutdown. On power-up, the LCD contrast counter and CCFL brightness counter are set to one-half scale.
The ICs are powered from a regulated 5V supply. The magnetics are connected directly to the battery, for maximum power efficiency.
The CCFL driver uses a Royer-type resonant architecture. It can provide from 100mW to 6W of power to one or two tubes. The MAX753 provides a negative LCD bias voltage; the MAX754 provides a positive LCD bias voltage.