PCF2119RU2DB2 datasheet(12/83 Pages) NXP

12 / 83 page

PCF2119X

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Product data sheet

Rev. 7 — 15 November 2010

12 of 83

NXP Semiconductors

PCF2119x

LCD controllers/drivers

The RMS on-state voltage (Von(RMS)) for the LCD is calculated with Equation 3 and the

RMS off-state voltage (Voff(RMS)) with Equation 4:

(3)

(4)

where the values of a are

a=2 for 1

⁄

4 bias

a=3 for 1

⁄

5 bias

and the values for n are

n = 2 for 1:2 multiplex rate

n = 9 for 1:9 multiples rate

n = 18 for 1:18 multiplex rate.

Discrimination (D) is the ratio of Von(RMS) to Voff(RMS) and is determined from Equation 5

(5)

8.5.1 Electro-optical performance

Suitable values for Von(RMS) and Voff(RMS) are dependant 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 Vlow) and the other at 90% relative transmission (at Vhigh), see Figure 3.

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

(6)

(7)

Table 6.

Bias levels as a function of multiplex rate

Multiplex

rate

Number of

bias levels

Bias voltages

1:18

VLCD

VSS

1:9

VLCD

VSS

1:2

VLCD

VSS

--- V

LCD

–

()

--- V

LCD

–

()

--- V

LCD

–

()

--- V

LCD

–

()

--- V

LCD

–

()

--- V

LCD

–

()

--- V

LCD

–

()

--- V

LCD

–

()

--- V

LCD

–

()

--- V

LCD

–

()

--- V

LCD

–

()

--- V

LCD

–

()

on RMS

()

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

LCD

off RMS

()

–

()

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

LCD

on RMS

()

off RMS

()

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

()

–

()

–

()

–

()

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

on RMS

()

high

≥

off RMS

()

low

≤

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