S1C63358 TECHNICAL MANUAL
EPSON
23
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Setting of Power Supply and Operating Mode)
4.2 Setting of Power Supply and Operating Mode
This section explains how to control the operating mode according to the supply voltage. Refer to Section
2.1, "Power Supply" for the configuration of the power supply circuit.
4.2.1 Control of supply voltage
When the voltage value necessary to drive the oscillation system voltage regulator is not provided from
the power supply voltage supplied externally, the S1C63358 drives the power supply circuit using the
voltage V
C2
generated by the LCD booster circuit. The supply voltage V
C2
is controlled using the register
LPWR.
• For normal operation:
Set LPWR = "0" or LPWR = "1", if LCD is used
• To use V
C2
supply voltage:
Set LPWR = "1"
The supply voltage V
C2
is common to the oscillation system voltage regulator and the A/D converter
voltage circuit. Therefore when using the V
C2
voltage for either of these circuits, turn on the LCD booster
circuit. The V
C2
voltage is output from the LCD booster circuit.
The oscillation system voltage regulator and the A/D converter voltage circuit can independently select
the drive voltage among V
DD
and V
C2
. This operation mode is controlled using the register VDSEL for
the oscillation system voltage regulator and the register VADSEL for the A/D converter voltage circuit.
By writing "1" to the register, V
C2
is selected as the drive voltage and writing "0" selects V
DD
. Approxi-
mately 100 msec is necessary until the V
C2
voltage stables after turning the LCD booster ON by the
LPWR. Therefore, the operating mode should be switched as in the following sequence.
Normal mode
→
V
C2
mode
1. Turn the LCD booster ON (set LPWR = "1").
2. Maintain 100 msec or more.
3. Set "1" in the VDSEL (for the oscillation system voltage regulator) or VADSEL (for the A/D converter
voltage circuit).
V
C2
mode
→
Normal mode
1. Set "0" in the VDSEL or VADSEL.
2. Turn the LCD booster OFF (set LPWR = "0" , if LCD is unused).
Note: • If the power supply voltage is out of the specified voltage range for an operating mode, do not
switch into the operating mode. It may cause malfunction or increase current consumption.
• When operating the S1C63358 with a 0.9–1.4 V power supply voltage, software control is
necessary. Set the oscillation system voltage regulator into the V
C2
mode. When 1.4 V or more
power supply voltage is used, don't set the oscillation system voltage regulator into the V
C2
mode. At initial reset the normal mode is set.
• When using the A/D converter circuit with a 0.9–1.6 V power supply voltage, software control is
necessary. Set the A/D converter circuit into the V
C2
mode. When 1.6 V or more power supply
voltage is used, don't set the A/D converter circuit into the V
C2
mode. At initial reset the normal
mode is set.
4.2.2 Operating mode for the oscillation system voltage regulator
and the internal operating voltage
The oscillation system voltage regulator generates the operating voltage V
D1
for the oscillation circuit and
internal logic circuits. This V
D1
voltage must be switched according to the oscillation circuit to be used.
Further the operating mode for the oscillation system voltage regulator must be switched depending on
the power supply voltage.
Control of V
D1
and the oscillation circuit will be explained in Section 4.4, "Oscillation Circuit". This
section explains the operating mode for the oscillation system voltage regulator that must be set before
controlling them. The following shows the setting contents according to the power supply voltage and
the oscillation circuit.
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