4 POWeR SuPPlY
4-2
Seiko epson Corporation
S1C17153 TeChniCal Manual
(Rev. 1.0)
2.2.1 V
Table 4.
C
Regulator Output Selection
Power supply voltage V
DD
VCSel setting
Reference voltage
2.0 to 2.2 (3.6) V
0
V
C1
2.2 to 3.6 V
1
V
C2
(Default: 0)
notes
: • The V
C1
to V
C3
voltages cannot be obtained correctly if VCSEL is set to 1 when V
DD
is 2.2 V or
less.
• Although the reference voltage can be set to V
C1
even if V
DD
is 2.2 V or higher, current
consumption will be increased in comparison with V
C2
.
Voltage booster/halver
When V
C1
is selected for the boosting/halving reference voltage, the voltage booster/halver generates V
C2
and
V
C3
by boosting V
C1
output from the V
C
regulator. When V
C2
is selected for the reference voltage, the voltage
booster/halver generates V
C1
by halving V
C2
and V
C3
by boosting V
C2
. The boosting operation uses a clock, so
it must be supplied to the LCD power supply circuit before LCD can start display.
Booster clock source selection
Select the clock source for the voltage booster/halver from OSC3B and OSC1A using LCDBCLKSRC[1:0]/
LCD_BCLK register.
2.2.2 Clock Source Selection
Table 4.
lCDBClKSRC[1:0]
Clock source
0x3, 0x2
Reserved
0x1
OSC1A
0x0
OSC3B
(Default: 0x0)
Booster clock division ratio selection
Select the division ratio using LCDBCLKD[2:0]/LCD_BCLK register. Set it so that the clock frequency
will be within the range from 512 Hz to 4 kHz.
2.2.3 Clock Division Ratio Selection
Table 4.
lCDBClKD[2:0]
Division ratio
Clock source = OSC3B
Clock source = OSC1a
0x7
Reserved
Reserved
0x6
1/4096
0x5
1/2048
0x4
1/1024
0x3
1/512
1/64
0x2
1/256
1/32
0x1
1/128
1/16
0x0
1/64
1/8
(Default: 0x0)
Booster clock enable
The booster clock supply is enabled with LCDBCLKE/LCD_BCLK register. The LCDBCLKE default
setting is 0, which stops the clock. Setting LCDBCLKE to 1 feeds the clock generated as above to the LCD
power supply circuit. If no LCD display is required, stop the clock to reduce current consumption.
heavy load Protection Mode
4.2.3
In order to ensure a stable circuit behavior and LCD display quality even if the power supply voltage fluctuates due
to driving an external load, the regulators have a heavy load protection function.
The table below lists the control bits used for setting heavy load protection mode.
