PCF8534 datasheet(8/40 Pages) PHILIPS

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PCF8534_0

Preliminary datasheet

Rev. 00.05 — 20 February 2007

8 of 40

NXP Semiconductors

PCF8534

Universal LCD driver for low multiplex rates

A practical value for VOP is determined by equating VOFF(rms) with a defined LCD threshold

voltage (VTH), typically when the LCD exhibits approximately 10% contrast. In the static

drive mode a suitable choice is VOP

> 3VTH.

Multiplex drive ratios of 1:3 and 1:4 with 1

⁄2 bias are possible but the discrimination and

hence the contrast ratios are smaller e.g.:

The advantage of these modes is a reduction of the LCD full-scale voltage VOP as follows:

• 1:3 multiplex (1

⁄2 bias):

• 1:4 multiplex (1

⁄2 bias):

These compare with VOP =3 x VOFF(rms) when 1

⁄3 bias is used. Note: VOP =VLCD.

1.732 for 1:3 multiplex or

----------

1.528

⎝⎠

⎛⎞

for 1:4 multiplex

OFF rms

()

2.449V

OFF rms

()

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

2.309V

OFF r ms

()

Table 5.

Preferred LCD drive modes: summary of characteristics

LCD drive

mode

Number of:

LCD bias

configuration

Backplanes

Levels

static

∞

1:2

⁄2

0.354

0.791

2.236

1:2

⁄3

0.333

0.745

2.236

1:3

⁄3

0.333

0.638

1.915

1:4

⁄3

0.333

0.577

1.732

OFF ms

()

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

ON ms

()

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

ON ms

()

OFF ms

()

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

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