User manual

...the world's most energy friendly microcontrollers
2012-04-24 - Giant Gecko Family - d0053_Rev0.96 788
www.energymicro.com
Table 33.6. LCD Principle of Contrast Adjustment for Different Bias Settings.
Contrast adjustment
relative to V
DD
(V
LCD
)
(CONCONF = 0)
Contrast adjustment
relative to GND
(CONCONF = 1)
No contrast adjustment
(CONLEV = 11111)
1/4 bias
V
LC0
V
LC1
V
LC2
V
LC3
R0
R1
R2
Rx
V
LCD_OUT
V
LCD
R3
V
LC4
V
LC0
V
LC1
V
LC2
V
LC3
R0
R1
R2
V
LCD
Rx
V
LCD_OUT
R3
V
LC4
V
LC0
V
LC1
V
LC2
V
LC3
R0
R1
R2
V
LCD
V
LCD_OUT
R3
V
LC4
1/3 bias
V
LC0
V
LC1
V
LC2
V
LC3
R0
R1
R2
Rx
V
LCD_OUT
V
LCD
V
LC0
V
LC1
V
LC2
V
LC3
R0
R1
R2
V
LCD
Rx
V
LCD_OUT
V
LC0
V
LC1
V
LC2
V
LC3
R0
R1
R2
V
LCD
V
LCD_OUT
1/2 bias
V
LC0
V
LC1
V
LC3
V
LCD
R0
R1
Rx
V
LCD_OUT
V
LC0
V
LC1
V
LC3
V
LCD
R0
R1
Rx
V
LCD_OUT
V
LC0
V
LC1
V
LC3
V
LCD
R0
R1
V
LCD_OUT
Static
V
LC0
V
LC3
V
LCD
R0
Rx
V
LCD_OUT
V
LC0
V
LC3
R0
V
LCD
Rx
V
LCD_OUT
V
LC0
V
LC3
V
LCD
V
LCD_OUT
R0 = R1 = R2 = R3 in the figure, while Rx is adjusted by changing the CONLEV bits.
33.3.5 V
LCD
Selection
By default, the LCD driver runs on main external power (V
LCD
= V
DD
), see Table 33.7 (p. 789) .
An internal boost circuit can be enabled by setting VBOOSTEN in CMU_LCDCTRL and selecting the
boosted voltage by setting VLCDSEL in LCD_DISPCTRL. This will boosts V
LCD
to V
BOOST
. V
BOOST
can
be selected in the range of 3.0 V – 3.6 V by configuring VBLEV in LCD_DISPCTRL. Note that the boost
circuit is not designed to operate with the selected boost voltage, V
BOOST
, smaller than V
DD
. The boost
circuit can boost the V
LCD
up to 3.6 V when V
DD
is as low as 2.0 V.
When using the voltage booster, the LCD_BEXT pin must be connected through a 1 µF capacitor to
VSS, and the LCD_BCAP_P and LCD_BCAP_N pins must be connected to each other through a 22
nF capacitor.