36.1 Description

The Segment Liquid Crystal Display Controller (SLCDC) drives a monochrome passive liquid crystal display (LCD) with up to 8 common terminals and up to 31 segment terminals.

An LCD consists of several segments (pixels or complete symbols) which can be visible or invisible. A segment has two electrodes with liquid crystal between them. When a voltage above a threshold voltage is applied across the liquid crystal, the segment becomes visible.

The voltage must alternate to avoid an electrophoresis effect in the liquid crystal, which degrades the display. Hence the waveform across a segment must not have a DC component.

The SLCDC is programmable to support many different requirements such as:

  • Adjusting the driving time of the LCD pads in order to save power and increase the controllability of the DC offset
  • Driving smaller LCD (down to 1 common by 1 segment)
  • Adjusting the SLCDC frequency in order to obtain the best compromise between frequency and consumption and adapt it to the LCD driver
  • Assigning the segments in a user defined pattern to simplify the use of the digital functions multiplexed on these pins
    Table 36-1. List of Terms
    TermDescription
    LCDA passive display panel with terminals leading directly to a segment
    SegmentThe least viewing element (pixel) which can be on or off
    Common(s)Denotes how many segments are connected to a segment terminal
    Duty1/(Number of common terminals on a current LCD display)
    Bias1/(Number of voltage levels used driving an LCD display -1)
    Frame RateNumber of times the LCD segments are energized per second