STE2004S Datasheet, PDF (12/79 Pages) STMicroelectronics – 102 x 65 single-chip LCD controller/driver

Circuit description
Table 3. Bias level m=65 and m=49
Symbol
m = 65 (1/9)
V1
V_LCD
V2
8/9*V_LCD
V3
7/9*V_LCD
V4
2/9*V V_LCD
V5
1/9 *V_LCD
V6
V_SS
STE2004S
m = 49 (1/8)
V_LCD
7/8*V_LCD
6/8*V_LCD
2/8*V_LCD
1/8*V_LCD
V_SS
3.6
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:
V_LCD(T=To) = V_LCDo = (Ai+V_OP · B)
with the following values:
(i=0,1,2)
Table 4. LCD voltage generation
Symbol
Value
Unit
Note
Ao
2.95
V
PRS = [0;0]
A1
6.83
V
PRS = [0;1]
A2
10.71
V
PRS = [1;0]
B
0.0303
V
To
27
°C
Note that the three PRS values produce three adjacent ranges for VLCD. If the V_OP 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:
VLCD
=
-----------¹----+----------^m------------- ⋅
2⋅
⎛
⎝
1
–
---¹--_m---_⎠⎞
Vth
For MUX Rate m = 65 the ideal V_LCD is:
V_LCD(to) = 6.85 · V_th
than:
Vop
=
(_---6_---._--8_---5_-----⋅_------V_{----t--h-----–-----}A_----i--)
0.03
12/79