PCF8531 datasheet(22/44 Pages) NXP

22 / 44 page

PCF8531_4

Product data sheet

Rev. 04 — 13 June 2008

22 of 44

NXP Semiconductors

PCF8531

34 x 128 pixel matrix driver

The practical value for VLCD is determined by equating Voff(RMS) with a deﬁned LCD

threshold voltage (Vth), typically when the LCD exhibits approximately 10 % contrast.

As the programming range for the internally generated VLCD allows values above the

maximum allowed VLCD, the user must ensure, while setting the VOP register and

selecting the temperature compensation, that the VLCD limit maximum of 9.0 V is never

exceeded under all conditions and including all tolerances.

9.10 Voltage multiplier control S[1:0]

The PCF8531 incorporates a software conﬁgurable voltage multiplier. After reset (internal

or external), the voltage multiplier is set to 2

× V

DD2. The voltage multiplier factors are set

by setting bits S[1:0] (see Table 13).

9.11 Temperature compensation

Due to the temperature dependency of the liquid crystal’s viscosity, the LCD controlling

voltage VLCD should usually be increased at lower temperatures to maintain optimum

contrast. Figure 12 shows VLCD for high multiplex rates.

Table 10.

Parameter values for the HV generator programming

Symbol

Value

Unit

PRS = 0

PRS = 1

Tints

°C

2.94

6.75

0.03

Programming range

2.94 to 6.75

6.75 to 10.56

VOP[6:0] (programmed) [00h to 7Fh] program range LOW to HIGH

Fig 11. VLCD programming of PCF8531

mgl935

VLCD

. . . 7D

. . . 5F

LOW

HIGH

PCF8531 Datasheet(PDF) 22 Page - NXP Semiconductors

PCF8531 Datasheet(HTML) 22 Page - NXP Semiconductors

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

Datasheet Download

Link URL