STE2002 datasheet(7/51 Pages) STMICROELECTRONICS

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STE2002

The STE2002 provides three bits (BS0, BS1, BS2) for programming the desired Bias Ratio as shown below:

The following table Bias Level for m = 65 and m = 81 are provided:

LCD Voltage Generation

The LCD Voltage at reference temperature (To = 27°C) can be set using the VOP register content according to

the following formula:

VLCD(T=To) = VLCDo = (Ai+VOP · B)

(i=0,1,2)

with the following values:

Note that the three PRS values produce three adjacent ranges for VLCD. If the VOP register and PRS bits are

set to zero the internal voltage generator is switched off.

The proper value for the VLCD is a function of the Liquid Crystal Threshold Voltage (Vth) and of the Multiplexing

Rate. A general expression for this is:

For MUX Rate m = 65 the ideal VLCD is:

VLCD(to) = 6.85 · Vth

than:

BS2

BS1

BS0

007

016

105

114

003

012

101

110

Symbol

m = 65 (1/9)

m = 81 (1/10)

VLCD

8/9*VLCD

9/10*VLCD

7/9*VLCD

8/10*VLCD

2/9*V VLCD

2/10*VLCD

1/9 *VLCD

1/10*VLCD

VSS

Symbol

Value

Unit

Note

2.95

PRS = [0;0]

6.83

PRS = [0;1]

10.71

PRS = [1;0]

0.0303

°C

LC D

---------

–





⋅

------------------------------------ V

⋅

6.85 V

–

⋅

()

0.03

-----------------------------------------

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