PCF8562 datasheet(9/36 Pages) PHILIPS

9 / 36 page

November 22, 2004

Philips Semiconductors

Preliminary specification

Universal LCD driver

for low multiplex rates

PCF8562

Discrimination is the ratio of Von to Voff, and is determined by the formula

Using the above formula, the discrimination for an LCD drive mode of 1 : 3 with 1

⁄2bias is

= 1.732, and the

discrimination for an LCD drive mode of 1 : 4 with 1

⁄2bias is

= 1.528.

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

• 1 : 3 multiplex (1⁄2 bias): VLCD =

= 2.449 Voff(rms)

• 1 : 4 multiplex (1⁄2 bias): VLCD =

= 2.309 Voff(rms)

These compare with VLCD = 3 Voff(rms) when 1

⁄3 bias is used.

Table 2

Discrimination ratios

LCD DRIVE MODE

NUMBER OF

LCD BIAS

CONFIGURATION

BACKPLANES

LEVELS

static

∞

1 : 2 multiplex

⁄2

0.354

0.791

2.236

1 : 2 multiplex

⁄3

0.333

0.745

2.236

1 : 3 multiplex

⁄3

0.333

0.638

1.915

1 : 4 multiplex

⁄3

0.333

0.577

1.732

off

---------

()

–

()

–

()

–

()

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

----------

off(rms)

()

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

off(rms)

lcd

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

on(rms)

lcd

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

on(rms)

off(rms)

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

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