The configuration for Liquid Crystal Display Multiplex Drive technique differs from a Static
Drive technique is that it uses more than a single "backplane" or segment
common. With this configuration, each segment control line can be connected
to as many segments as there are backplanes, providing that each of the
segments that it is connected to are tied to a separate backplanes.
This method "Multiplexes" each of the segment control lines and minimizes
the number of interconnects. This is the method used with complex
displays that have limited interconnection surface area or available drive
circuits. This reduction in the number of external connections
enhances device reliability and increases the potential display density. The
liability of a higher multiplex rate will effect display quality,
operational temperature range, and the increased complexity of drive
circuitry (or perhaps microprocessor software) may necessary for their
The control signals that drive an LCD are AC in nature. The basic configuration of how to generate a waveform to control an LCD are covered in the sections "LCD Multiplex Ratio (above)" and "LCD Static Drive Technology". But to control LCDs with a larger multiplex ratio, we need to provide the waveform generator with multiple bias voltage level points. The resulting waveform sent to the LCD segment/dot control lines and backplane commons will contain a stair-stepped waveform that will maintain specific ac voltages across any given segment/dot to keep it in it's "on" or "off" state (or in a grayscale module, states between those two points). The LCD Bias number (example: 1/5 bias) will indicate how many voltage reference points are created to drive a specific LCD. The table below shows the relationship between the number of driving bias voltages and the display multiplex ratios typically used:
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