LCD_F Controller Architecture and Operation
1006
SLAU356I – March 2015 – Revised June 2019
Copyright © 2015–2019, Texas Instruments Incorporated
LCD_F Controller
Table 27-2. Bias Voltages and External Pins
Mode
Bias
LCD2B
Voltage Level
Pin
Condition
Static
Static
X
V1 ("1")
V1 = V
CC
(internally sourced)
V5 ("0")
R03
R03EXT = 1
2-mux, 3-mux, 4-mux
1/2
1
V1 ("1")
V1 = V
CC
(internally sourced)
V3 ("1/2")
R13
LCDREXT = 1 or LCDEXTBIAS = 1
V5 ("0")
R03
R03EXT = 1
2-mux, 3-mux, 4-mux
1/3
0
V1 ("1")
V1 = V
CC
(internally sourced)
V2 ("2/3")
R23
LCDREXT = 1 or LCDEXTBIAS = 1
V4 ("1/3")
R13
LCDREXT = 1 or LCDEXTBIAS = 1
V5 ("0")
R03
R03EXT = 1
5-mux to 8-mux
1/3
0
V1 ("1")
V1 = V
CC
(internally sourced)
V2 ("2/3")
R23
LCDREXT = 1 or LCDEXTBIAS = 1
V4 ("1/3")
R13
LCDREXT = 1 or LCDEXTBIAS = 1
V5 ("0")
R03
R03EXT = 1
5-mux to 8-mux
1/4
1
V1 ("1")
V1 = V
CC
(internally sourced)
V2 ("3/4")
R23
LCDREXT = 1 or LCDEXTBIAS = 1
V3 ("2/4")
R13
LCDREXT = 1 or LCDEXTBIAS = 1
V4 ("1/4")
R03
LCDREXT = 1 or LCDEXTBIAS = 1
V5 ("0")
Not available on
pin
27.2.5.6.2 LCD Contrast Ratio Control
The peak voltage of the output waveforms (V1 = V
CC
) together with the selected mode and biasing
determine the contrast and the contrast ratio of the LCD.
The contrast ratio depends on the used LCD display and the selected biasing scheme.
lists the
biasing configurations that apply to the different modes together with the RMS voltages for the segments
turned on (V
RMS,ON
) and turned off (V
RMS,OFF
) as functions of V
LCD
(V
LCD
= V
CC
). The table also lists the
resulting contrast ratios between the on and off states.
(1)
Recommended setting to achieve best contrast
Table 27-3. LCD Voltage and Biasing Characteristics
Mode
Bias
LCDMx
LCD2B
COM
Lines
Voltage Levels
V
RMS,OFF
/ V
LCD
V
RMS,ON
/ V
LCD
Contrast
Ratio V
RMS,ON
/
V
RMS,OFF
Static
Static
0000
X
1
V1, V5
0
1
1/0
2-mux
1/2
(1)
0001
1
2
V1, V3, V5
0.354
0.791
2.236
1/3
0001
0
2
V1, V2, V4, V5
0.333
0.745
2.236
3-mux
1/2
0010
1
3
V1, V3, V5
0.408
0.707
1.732
1/3
(1)
0010
0
3
V1, V2, V4, V5
0.333
0.638
1.915
4-mux
1/2
0011
1
4
V1, V3, V5
0.433
0.661
1.528
1/3
(1)
0011
0
4
V1, V2, V4, V5
0.333
0.577
1.732
5-mux
1/3
(1)
0100
0
5
V1, V2, V4, V5
0.333
0.537
1.612
1/4
0100
1
5
V1, V2, V3, V4, V5
0.316
0.500
1.581
6-mux
1/3
(1)
0101
0
6
V1, V2, V4, V5
0.333
0.509
1.528
1/4
0101
1
6
V1, V2, V3, V4, V5
0.306
0.468
1.528