PC85232-1 查看數據表（PDF） - NXP Semiconductors.

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PC85232-1

LCD driver for low multiplex rates

NXP Semiconductors. 

NXP Semiconductors

PCF85132

LCD driver for low multiplex rates

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.

7.3.1 Electro-optical performance

Suitable values for Von(RMS) and Voff(RMS) are dependant on the LCD liquid used. The

RMS voltage, at which a pixel will be switched on or off, determine the transmissibility of

the pixel.

For any given liquid, there are two threshold values defined. One point is at 10 % relative

transmission (at Vlow) and the other at 90% relative transmission (at Vhigh), see Figure 5.

For a good contrast performance, the following rules should be followed:

Von(RMS) ≥ Vhigh

(4)

Voff(RMS) ≤ Vlow

(5)

Von(RMS) and Voff(RMS) are properties of the display driver and are affected by the selection

of a, n (see Equation 1 to Equation 3), and the VLCD voltage.

Vlow and Vhigh are properties of the LCD liquid and can be provided by the module

manufacturer.

It is important to match the module properties to those of the driver in order to achieve

optimum performance.

PCF85132

Product data sheet

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

Rev. 1 — 23 November 2010

© NXP B.V. 2010. All rights reserved.

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