PCF8576DTSLASHS400SLASH2 datasheet(10/57 Pages) NXP

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PCF8576D

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Product data sheet

Rev. 14 — 10 June 2013

10 of 57

NXP Semiconductors

PCF8576D

Universal LCD driver for low multiplex rates

(3)

Using Equation 3, the discrimination for an LCD drive mode of 1:3 multiplex with

1⁄2 bias is

and the discrimination for an LCD drive mode of 1:4 multiplex with

1⁄2 bias is

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):

• 1:4 multiplex (1⁄2 bias):

These compare with

when 1⁄3 bias is used.

It should be noted that VLCD is sometimes referred as the LCD operating voltage.

7.3.1 Electro-optical performance

Suitable values for Von(RMS) and Voff(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 Vth(off)) and the other at 90 % relative transmission (at Vth(on)), see

Figure 6. For a good contrast performance, the following rules should be followed:

(4)

(5)

Von(RMS) and Voff(RMS) are properties of the display driver and are affected by the selection

of a, n (see Equation 1 to Equation 3) and the VLCD voltage.

Vth(off) and Vth(on) are properties of the LCD liquid and can be provided by the module

manufacturer. Vth(off) is sometimes just named Vth. Vth(on) is sometimes named saturation

voltage Vsat.

It is important to match the module properties to those of the driver in order to achieve

optimum performance.

on RMS



off RMS



-----------------------

–

---------------------------

1.732

----------

1.528

LCD

off RMS





2.449V

off RMS



LCD





----------------------

2.309V

off RMS



LCD

off RMS



on RMS



th on





off RMS



th off





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