PCF85162 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 5 — 17 December 2014 13 of 53
NXP Semiconductors
PCF85162
32 × 4 universal LCD driver for low multiplex rates
The advantage of these LCD drive modes is a reduction of the LCD full scale voltage V
LCD
as follows:
• 1:3 multiplex (
1
⁄
2
bias):
• 1:4 multiplex (
1
⁄
2
bias):
These compare with when
1
⁄
3
bias is used.
It should be noted that V
LCD
is sometimes referred as the LCD operating voltage.
7.3.3.1 Electro-optical performance
Suitable values for V
on(RMS)
and V
off(RMS)
are dependent on the LCD liquid used. The
RMS voltage, at which a pixel will be switched on or off, determine the transmissibility of
the pixel.
For any given liquid, there are two threshold values defined. One point is at 10 % relative
transmission (at V
th(off)
) and the other at 90 % relative transmission (at V
th(on)
), see
Figure 5
. For a good contrast performance, the following rules should be followed:
(4)
(5)
V
on(RMS)
and V
off(RMS)
are properties of the display driver and are affected by the selection
of a, n (see Equation 1
to Equation 3) and the V
LCD
voltage.
V
th(off)
and V
th(on)
are properties of the LCD liquid and can be provided by the module
manufacturer. V
th(off)
is sometimes just named V
th
. V
th(on)
is sometimes named saturation
voltage V
sat
.
It is important to match the module properties to those of the driver in order to achieve
optimum performance.
V
LCD
6V
off RMS
2.449V
off RMS
==
V
LCD
43
3
----------------------
2.309V
off RMS
==
Fig 5. Electro-optical characteristic: relative transmission curve of the liquid
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