PCF8536AT datasheet(17/54 Pages) NXP

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PCA85233

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Product data sheet

Rev. 5 — 12 November 2018

17 of 54

NXP Semiconductors

PCA85233

Automotive 80 × 4 LCD driver for low multiplex rates

7.7.1 Electro-optical performance

Suitable values for Von(RMS) and Voff(RMS) are dependent 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 Vth(off)) and the other at 90 % relative transmission (at Vth(on)), see

Figure 8. For a good contrast performance, the following rules should be followed:

(7)

(8)

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

of a, n (see Equation 4 to Equation 6) and the VLCD voltage.

Vth(off) and Vth(on) are properties of the LCD liquid and can be provided by the module

manufacturer. Vth(off) is sometimes named Vth. Vth(on) is sometimes named saturation

voltage Vsat.

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

optimum performance.

Fig 8.

Electro-optical characteristic: relative transmission curve of the liquid

on RMS



th on





off RMS



th off





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