Datasheet

Chapter 9 Liquid Crystal Display Driver (S08LCDV1)
MC9S08LC60 Series Data Sheet: Technical Data, Rev. 4
Freescale Semiconductor 153
9.4.4.2 LCD Power Supply and Voltage Buffer Configuration
The LCD power supply can be internally derived from V
DD
or it can be externally derived from a voltage
source in the range between 0.9 to 1.8 Volts that is applied to the V
LCD
pin. The Table below provides a
more detailed description of the power state of the LCD module which depends on the configuration of the
VSUPPLY[1:0], LCDCPMS, BBYPASS, and LCDCPEN bits.
Figure 9-18 shows that if VSUPPLY[1:0] = 10 or 11, the LCD module is configured for an external power
source. If VSUPPLY[1:0] = 00 or 01, the LCD power supply is configured to be internally derived from
V
DD
.
9.4.4.2.1 LCD External Power Supply, VSPUPPLY[1:0] = 10
When VSPUPPLY[1:0] = 10, only the powersw3 signal is asserted and the LCD module is configured to
be powered via an external voltage input on V
LCD
(Recall V
LCD
is specified to be in the range from 0.9 V
to 1.8 V). The figure above shows that V
LCD
is an input to the voltage divider block and is related to V
LL1.
The voltage divider block uses the states of LCDCPMS, BBYPASS, and powersw3 to derive a state for
V
LL1
.
Table 9-18. V
DD
Switch Option
VSUPPLY[1:0]
LCDCPMS
BBYPASS
LCDCPEN
LCD Power Supply Configuration
LCD Operational State
00 X X
0 Initial V
LL2
voltage to V
DD
level. LCD disabled
1
Internal power supply.
V
LL2
is generated from V
DD
.
LCD operational
01
XX
0 Initial V
LL3
voltage to V
DD
level. LCD disabled
1
Internal power supply.
V
LL3
is generated from V
DD
.
LCD operational
Minimum current consumption
10
x x 0 Bias voltages not generated. LCD disabled
001
External power supply for V
LCD
.
Buffered doubler mode.
LCD operational
Maximum current consumption
011
External power supply for V
LCD
.
Un-buffered doubler mode.
LCD operational
101
External power supply for V
LCD
.
Buffered tripler mode.
LCD operational
111
External power supply for V
LCD
.
Un-buffered tripler mode.
LCD operational
Minimum current consumption
11 X X
0
External power supply for V
LL1
,V
LL2
, and VLL3 required.
V
LCD
pin floating.
LCD Operational
1V
LCD
pin floating. Invalid LCD power configuration