PCF8548 datasheet(19/40 Pages) PHILIPS

19 / 40 page

1999 Aug 16

Philips Semiconductors

Product speciﬁcation

× 102 pixels matrix LCD driver

PCF8548

12.6

Set X address of RAM

The X address points to the columns. The range of X is

0 to 101 (65H).

12.7

Set HV generator stages

12.7.1

S[1:0]

The PCF8548 incorporates a software configurable

voltage multiplier. After reset the voltage multiplier is set to

× VDD2. Other voltage multiplier factors are set via the

command ‘set HV-gen stages’ (see Tables 1 and 2).

12.8

Temperature control

Due to the temperature dependency of the liquid crystals

viscosity, the LCD controlling voltage VLCD must be

increased with lower temperature to maintain optimum

contrast.

There are 4 different temperature coefficients available in

the PCF8548 (see Fig.15). The coefficients are selected

by the two bits TC[1:0]. Table 6 shows the typical values of

the different temperature coefficients. The coefficients are

proportional to the programmed VLCD.

12.9

Bias system

The Bias voltage levels are set in the ratio

of R

− R − nR − R − R giving a

bias system.

The resulting bias levels are shown in Table 5.

Different multiplex rates require different factors n (see

Table 4); this is programmed by BS[2 : 0]. For Mux1:65

the optimum bias value n is given by:

resulting in 1

⁄

9bias.

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

–

5.06

Fig.15 Temperature coefficients.

handbook, halfpage

MGS402

VLCD

Tcut

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