PCF8811USLASH2DASLASH1 datasheet(49/81 Pages) NXP

49 / 81 page

PCF8811_4

Product data sheet

Rev. 04 — 27 June 2008

49 of 81

NXP Semiconductors

PCF8811

80 x 128 pixels matrix LCD driver

12.10 Set VOP value

For multiplex rate 1:80 the optimum operation voltage of a liquid can be calculated with the

variables given in Table 25, Equation 1 and Equation 2.

(3)

Where VTH is the threshold voltage of the liquid crystal material used.

The programming method for the VOP value is implemented differently in the basic

command set from that in the extended command set. In the basic command set two

commands are sent to the PCF8811: namely VPR[5:0] and VOFF[2:0]. In the extended

command set only one command VPR[7:0] is sent to the PCF8811. The programming of

VOP in the basic command set can be used when the PCF8811 is used as a replacement

for an IAPT (Improved Alt-Pleshko Technique) LCD driver. The ROM look-up table

Table 28 shows the possible values for VOFF[2:0], VPR[5:0], VOP[7:0] and VLCD.

12.10.1 Basic command set

The VLCD at T = TCUT in the basic command set is determined by the conversion in the

ROM look-up table with the programmed values of VPR[5:0] and VOFF[2:0]. It can,

additionally, be adjusted with the VLCD offset pads VOS[4:0] to obtain the optimum optical

performance.

Example: To get the value of 6 V for VLCD the following values have to be taken;

see Table 26.

Table 25.

Relationship between multiplex rates and bias setting variables with the icon row

(only extended command set)

Multiplex rate

Variable

1:16

1:32

1:48

1:64

1:80

LCD

-------

------

–

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

4.472

Fig 35. Setting of VOP in the basic and extended command set

mgw753

VLCD

LOOK-UP

TABLE

ROM

MMVOPCAL[4:0]

VOS[4:0]

VOP[7:0]

VPR[7:0]

rom_add[8:0]

VPR[5:0]

VOFF[2:0]

EXT

EXT = 1

EXT = 0

7 6 5 4 3 2 1 0 2 1 0

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