R13
R23
R03
1
0
V1 (V
)
LCD
V2
(2/3 or 3/4 V
)
LCD
V5
0
R03EXT
R
R
R
R
R
Rx
R
1/3 Bias 1/4 Bias
Optional external resistors
Rx = Optional contrast control
LCDMXx = 100b, 101b, 110b, or 111b
5-Mux, 6-Mux, 7-Mux, or 8-Mux Mode
LCD2B LCDEXTBIAS
1
1
1
LCDREXT
V3 (2/4 V
)
LCD
V4
(1/3 or 1/4 V
)
LCD
V
CC
V
CC
V
CC
R
1
LCD_F Controller Architecture and Operation
1005
SLAU356I – March 2015 – Revised June 2019
Copyright © 2015–2019, Texas Instruments Incorporated
LCD_F Controller
Figure 27-6. Bias Generation for 5-Mux to 8-Mux Mode, 1/3-Bias and 1/4-Bias in LCD
The internally generated bias voltages V2 to V4 are output on external pins if LCDREXT = 1.
To source the bias voltages V2 to V4 externally, LCDEXTBIAS is set. This also disables the internal bias
generation. Typically, an equally weighted resistor divider is used with resistors ranging from a few k
Ω
to
1 M
Ω
, depending on the size of the display. In static, 2-mux, 3-mux , 4-mux mode and 1/3-bias setting in
5- to 8-mux modes, V5 can also be sourced externally when R03EXT is set to control the contrast of the
connected display by changing the voltage at the low end of the external resistor divider as shown in the
left part of
In 2-mux, 3-mux, and 4-mux modes, the bias generator supports 1/2 biasing when LCD2B = 1 and 1/3
biasing when LCD2B = 0. In 5-mux to 8-mux modes, the bias generator supports 1/4 biasing when
LCD2B = 1 and 1/3 biasing when LCD2B = 0. In static mode, the internal divider is disabled.