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Maxim > Design Support > Technical Documents > Application Notes > Digital Potentiometers > APP 3467
Maxim > Design Support > Technical Documents > Application Notes > Display Drivers > APP 3467
Keywords: LCD drivers, SMBus, I/O expanders, digital potentiometers, stepup converters
APPLICATION NOTE 3467
SMBus I/O Expander Controls LCD Bias Voltage
By: Jim Christensen, Strategic Applications Engineer
Mar 14, 2005
Abstract: A circuit consisting of an SMBus™ I/O expander, step-up converter, and digital potentiometer
enables the SMBus to control the contrast of an LCD.
Small, handheld, battery-powered devices often feature an LCD panel and a microcontroller with limited
I/O pins. The SMBus is useful for controlling system functions under limited I/O and, for convenience, it
should also be able to control the LCD contrast. In Figure 1, this task is accomplished with an SMBus
I/O expander (IC2), a step-up converter (IC1), and a digital potentiometer (IC3).
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