PCF8562TT/2(2008) 查看數據表（PDF） - NXP Semiconductors.

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PCF8562TT/2
(Rev.:2008)

Universal LCD driver for low multiplex rates

NXP Semiconductors. 

NXP Semiconductors

PCF8562

Universal LCD driver for low multiplex rates

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-V-----oo--f-n-f-(-(-R-R--M-M---S-S--)-) = -((--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 and the discrimination for an LCD drive mode of 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.

PCF8562_3

Product data sheet

Rev. 3 — 2 December 2008

© NXP B.V. 2008. All rights reserved.

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