See Microchip Appnote for TC7660<\/a><\/p>\nDriving the contrast voltage from a PWM output is a recommended solution => Button contrast control. If an on board temperature sensor is present, you can even have an automatic contrast\/temperature adjustment when not using an extended temperature grade device.<\/p>\n
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LCD CONTRAST ADJUSTMENT WITH TEMP COMPENSATION<\/span><\/p>\nDue to the contrast versus voltage versus temperature characteristics of liquid crystal fluids, and the sensitive nature of display drive voltage during multiplex operation, it may become necessary to compensate the LCD drive voltage for applications where the display is subjected to wide temperature excursions. For a typical Liquid Crystal fluid, with a negative temperature coefficient, an under voltage condition with diminished display contrast will result at low temperatures, and a “ghosting” or overdrive condition will occur at high temperatures, if no compensation techniques are employed. So if your application requires good contrast over a large temperature range, you may need to consider temperature compensation for your contrast adjustment circuitry.<\/p>\n
When using an LCD module, one solution is to order an automatic temperature compensation option ( if available)<\/p>\n\t