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PC8533-2

Universal LCD driver for low multiplex rates

NXP Semiconductors. 

NXP Semiconductors

PCF8533

Universal LCD driver for low multiplex rates

n = 1 for static drive mode

n = 2 for 1:2 multiplex drive mode

n = 3 for 1:3 multiplex drive mode

n = 4 for 1:4 multiplex drive mode

The RMS off-state voltage (Voff(RMS)) for the LCD is calculated with Equation 2:

Voff(RMS)

=

VLCD

--a---2----–----2----a----+-----n---

n × (1 + a)2

(2)

Discrimination is the ratio of Von(RMS) to Voff(RMS) and is determined from Equation 3:

D

=

-V----o---n--(--R---M----S---)

Voff(RMS)

=

(---a-----+-----1----)--2----+-----(--n-----–----1----)

(a – 1)2 + (n – 1)

(3)

Using Equation 3, the discrimination for an LCD drive mode of 1:3 multiplex with

1⁄2 bias is 3 = 1.732 and the discrimination for an LCD drive mode of 1:4 multiplex with

1⁄2 bias is

-----2---1--

3

=

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 = 6 × Voff(RMS) = 2.449Voff(RMS)

• 1:4 multiplex (1⁄2 bias): VLCD =

(---4-----×---------3----)

3

= 2.309Voff(RMS)

These compare with VLCD = 3Voff(RMS) when 1⁄3 bias is used.

It should be noted that VLCD is sometimes referred as the LCD operating voltage.

PCF8533_4

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 04 — 5 March 2010

© NXP B.V. 2010. All rights reserved.

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