PCF8811USLASH2DASLASH1 datasheet(37/73 Pages) PHILIPS

37 / 73 page

2004 May 17

Philips Semiconductors

Product speciﬁcation

× 128 pixels matrix LCD driver

PCF8811

Table 19 Bias levels for MRA driving method

SYMBOL

BIAS VOLTAGES

DC SHIFTED BIAS VOLTAGES

F=Gmax

VLCD

FVLCD

V3_H

V2_H

V1_H

1/2VLCD

V1_L

V2_L

V3_L

VSS

−FV

–

()

–

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

LCD

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

–

()

–

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





–

()

–

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

LCD

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

–

()

–

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





–

()

–

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

LCD

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

–

()

–

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





–

()

–

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

LCD

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

–

()

–

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

–





–

()

–

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

LCD

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

–

()

–

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

–





–

()

–

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

LCD

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

–

()

–

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

–





The row voltages (F) are not necessarily larger then the

column voltages. This depends on the number of rows

which are selected, the multiplexibility and the value of p.

However, the PCF8811 is designed in such a way that the

maximum column voltages are always equal to the row

voltages. In Table 20 the VLCD and the different bias levels

are given for the PCF8811. The VLCD voltage is defined as:

(2)

Where F is defined in (1)

The bias system settings for different display modes are

given in Table 20. All bias levels can be calculated by

using the third column of Table 19 and the variables given

in Table 20. Programming of the bias levels is not

necessary in the PCF8811. The selection of the

appropriate bias level voltages for each display mode is

done automatically. Only the appropriate VLCD voltage

must be programmed according to equations (1) and (2)

for the display modes listed in Table 20.

The variables for calculating VLCD, when the icon row is

enabled, are given in Table 21. The icon row can only be

addressed in the extended command set.

The PCF8811 allows the value of p, for certain mux rates,

to be chosen manually.

This is only possible for the mux rates 1 : 64 and 1 : 80.

If other mux rates are chosen the PCF8811 determines

the optimum value of p. By setting the value of p manually

a compromise can be made between contrast and power

consumption with certain liquids for the high mux rates

1 : 64 and 1 : 80. However, care must be taken that the

liquid which is chosen ensures that the row voltages (F)

and the maximum column voltages are equal.

Table 20 Relationship between mux rates and bias

setting variables without icon row

LCD

MUX RATE

1:16

1:24

1:32

1:40

1:48

1:56

1:64

1:72

1:80

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