NXP Semiconductors
PCF8532
Universal LCD driver for low multiplex rates
V-V-----oo--fn--f-(-(-R-R--M-M---S-S--)-) = (-(--aa-----+–-----11---)-)--22----++-----((--nn----–-–----11----))
(3)
Using Equation 3, the discrimination for an LCD drive mode of
• 1:3 multiplex with 1⁄2 bias is 3 = 1.732
• 1:4 multiplex with 1⁄2 bias is ----3-2---1-- = 1.528
The advantage of these LCD drive modes is a reduction of the LCD full scale voltage VLCD
as follows:
• 1:3 multiplex (1⁄2 bias):V LCD = 6 × V off (RMS) = 2.449V off (RMS)
• 1:4 multiplex (1⁄2 bias): V LCD = (---4-----×--3-------3----) = 2.309V off (RMS)
These compare with V LCD = 3V off (RMS) when 1⁄3 bias is used.
It should be noted that VLCD is sometimes referred as the LCD operating voltage.
PCF8532_1
Product data sheet
Rev. 1 — 10 February 2009
© NXP B.V. 2009. All rights reserved.
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