PC85133-1(2009) 查看數據表（PDF） - NXP Semiconductors.

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PC85133-1
(Rev.:2009)

Universal LCD driver for low multiplex rates

NXP Semiconductors. 

NXP Semiconductors

PCF85133

Universal LCD driver for low multiplex rates

The RMS on-state voltage (Von(RMS)) for the LCD is calculated with the equation

V on(RMS)

=

V LCD

-1n- + (n – 1) × 1-----+1-----a-- 2

-----------------------------n-------------------------------

(1)

where VLCD is the resultant voltage at the LCD segment and where the values for n are

n = 1 for static mode

n = 2 for 1:2 multiplex

n = 3 for 1:3 multiplex

n = 4 for 1:4 multiplex

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

V off (RMS) = V LCD -a-n--2---×-–---(--(-1-2----a+-----+a---)-n--2--)

(2)

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

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

Voff (RMS)

-((--aa-----+–-----11---)-)--22----++-----((--nn----–-–----11----))

(3)

Using Equation 3, the discrimination for an LCD drive mode of

• 1:3 multiplex with 1⁄2 bias is 3 = 1.732

• 1:4 multiplex with 1⁄2 bias is ----3-2---1-- = 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):V LCD = 6 × V off (RMS) = 2.449V off (RMS)

• 1:4 multiplex (1⁄2 bias): V LCD = (---4-----×--3-------3----) = 2.309V off (RMS)

These compare with V LCD = 3V off (RMS) when 1⁄3 bias is used.

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

PCF85133_1

Product data sheet

Rev. 1 — 17 February 2009

© NXP B.V. 2009. All rights reserved.

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