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4 POWeR SuPPlY
internal logic voltage regulator
The internal logic voltage regulator generates the V
lators. The V
voltage value can be switched in the program; set it to 1.8 V for normal operation and 2.5 V for
D1
Flash programming.
lCD system voltage regulator
The LCD system voltage regulator generates the 1/3-bias LCD drive voltages V
S1C17624/604/622/602/621, the LCD drive voltage is supplied to the built-in LCD driver that drives the LCD
panel connected to the SEG and COM pins. The reference voltage (V
reducer should be selected using VCSEL/LCD_VREG register according to the power supply voltage V
compared to the V
reference voltage, the V
C1
to V
voltage values, see the "Electrical Characteristics" chapter.
C3
note: The V
to V
C1
C3
less.
4.4
Controlling the Power Supply Circuit
In order to generate the internal operating voltage properly according to the power supply voltage and operating
mode, or to reduce current consumption, the power supply circuit is designed to be controlled with software.
Switching the operating mode
The S1C17624/604/622/602/621 has two kinds of operating modes.
1. Normal operating mode
This mode is provided for running the application program.
V
= 1.8 to 3.6 V, internal operating voltage V
DD
2. Flash erase/programming mode
This mode is provided for erasing and programming the Flash memory.
V
= 2.7 to 3.6 V, internal operating voltage V
DD
The V
voltage value must be switched according to the operating mode as shown above using VD1MD/VD1_
D1
CTL register. Normally set VD1MD to 0 (V
gramming the Flash memory.
note: When the V
voltage is switched, the V
D1
programming should be started after the stabilization time has elapsed.
Controlling the lCD power source
The LCD drive voltages V
register to a value other than 0x0 (display off).
When the internal LCD driver is not used, the LCD system voltage regulator should be turned off (DSPC[1:0] =
0) to reduce current consumption.
Power control bit settings
Table 4.4.1 lists the power control bit settings in different operating conditions.
Operating mode
Normal
operating mode
4-2
C2
Table 4.
3.2 Power Supply Voltage V
Power supply voltage V
DD
1.8 to 3.6 V
2.5 to 3.6 V
voltages cannot be obtained correctly if VCSEL is set to 1 when V
D1
to V
will be supplied to the LCD driver by setting the DSPC[1:0]/LCD_DCTL
C1
C3
Table 4.
4.1 Power Control Bit Settings
Condition
V
lCD driver
DD
1.8 to 3.6 V
2.5 to 3.6 V
1.8 to 3.6 V
Not used
Seiko epson Corporation
operating voltage for the internal logic circuits and oscil-
D1
C1
reference voltage is lower in current consumption. For the V
and VCSEL Settings
DD
VCSEL setting Reference voltage
0
1
= 1.8 V
D1
= 2.5 V
D1
= 1.8 V, default setting). It should be set to 1 before erasing/pro-
voltage requires 5 ms (max.) to stabilize. Flash memory
D1
VD1MD
Used
0
Used
0
0
S1C17624/604/622/602/621 TeChniCal Manual
, V
, and V
C1
C2
or V
) for the LCD voltage booster/
C2
V
C1
V
C2
(Default: 0)
DD
Control bits
VCSel
DSPC[1:0]
0
Other than 0x0
1
Other than 0x0
0
0x0
. In the
C3
. As
DD
C1
is 2.5 V or
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