5 POWeR SuPPlY
S1C63003/004/008/016 TeChniCal Manual
Seiko epson Corporation
5-3
(Rev. 1.1)
Notes: • Do not use the V
D1
, V
OSC
, and V
C1
to V
C3
terminal output voltages to drive external circuits.
• When 1/2 bias is selected, the V
C1
and V
C2
pins are connected inside the IC.
Controlling lCD Power Supply
5.3
The LCD system voltage regulator generates the reference voltage V
C1
or V
C2
and generates two other voltages (V
C2
= V
C1
×
2, V
C3
= V
C1
×
3, or V
C1
= V
C2
×
1/2, V
C3
= V
C2
×
3/2) by boosting or reducing V
C1
/V
C2
.
The reference voltage to be generated should be selected from V
C1
and V
C2
according to the supply voltage V
DD
.
In the S1C63004/008/016, use the VCREF register to select the reference voltage with consideration given to the
contrast of display in addition to the supply voltage. In the S1C63003, it can be selected by mask option. Also refer
to the LCD drive voltage - supply voltage characteristics (in the “Electrical Characteristics - Characteristics Curves”
section) and select the appropriate reference voltage according to the system.
To generate the LCD drive voltages by the LCD system voltage regulator (to start LCD display), turn the LCD system
voltage regulator on using the LPWR register. When "1" is written to LPWR, the LCD system voltage regulator goes
on and generates the LCD drive voltages. At initial reset, LPWR is set to "0" (Off).
When LCD display is not needed, turn the LCD system voltage regulator off to reduce power consumption.
Notes: • The LCD system voltage regulator takes about 100 msec for stabilizing the LCD drive voltages
after writing "1" to LPWR.
• Do not select the reference voltage V
C2
for the S1C63003 1.5 V low-voltage type.
Furthermore, the LCD system voltage regulator uses the boost clock supplied from the clock manager for boosting/
reducing the voltage. The clock supply is controlled by the VCCKS[1:0] register. Set VCCKS[1:0] to "1" before
writing "1" to LPWR. When LCD display is not necessary, stop the clock supply by setting VCCKS[1:0] to "0" to
reduce power consumption.
3.1 Controlling boost clock
Table 5.
VCCKS[1:0]
Boost clock control
3 or 2
Prohibited
1
On (2 kHz)
0
Off
heavy load Protection Function
5.4
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 internal operating voltage regulator and the LCD system voltage regulator have a heavy
load protection function.
The internal operating voltage regulator enters heavy load protection mode by writing "1" to the VDHLMOD register
and it ensures stable V
D1
output. Use the heavy load protection function when a heavy load such as a lamp or buzzer
is driven with a port output.
The LCD system voltage regulator enters heavy load protection mode by writing "1" to the VCHLMOD register and
it ensures stable V
C1
–V
C3
outputs. Use the heavy load protection function when the LCD display has inconsistencies
in density.
Note: Current consumption increases in heavy load protection mode, therefore do not set heavy load
protection mode with software if unnecessary.