S1C63666 TECHNICAL MANUAL
EPSON
25
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Power Control)
4.2 Power Control
4.2.1 Configuration of power supply circuit
The S1C63666 has built-in power supply circuits shown in Figure 4.2.1.1 so the voltages to drive the CPU,
internal logic circuits, oscillation circuits and LCD driver can be generated on the chip.
External
power
supply
LCD system
voltage regulator
LCD driver
CC
CD
V
DDA
V
DD
V
D2
V
C1
V
C2
V
C3
CA
CB
V
OSC
V
D1
V
SS
V
SSA
V
C1
V
C1
V
C2
V
C3
V
D1L
V
OSC
V
D3
V
D2
=1/2 V
DD
V
D1
Voltage
halver
Voltage booster
LCD system voltage circuit
LPWR
VDC3
VDC2
VDC0
VDC1
Low-speed operation
voltage regulator
Voltage regulator for
OSC1 oscillation circuit
OSC1
oscillation circuit
CPU,
internal circuits
R/f
converter
High-speed operation
voltage regulator
OSC3
oscillation circuit
+
Fig. 4.2.1.1 Built-in power supply circuit
Voltage regulator for OSC1 oscillation circuit
This voltage regulator always operates to generate the V
OSC
voltage (0.98 V Typ.) for driving the
OSC1 oscillation circuit.
Low-speed operation voltage regulator
The low-speed operation voltage regulator always operates to generate the V
D1L
voltage (1.25 V Typ.)
for driving the internal logic circuits. The V
D1L
voltage is used as the V
D1
operating voltage of the
CPU and internal logic circuits when they are driven with the OSC1 clock (32 kHz). V
D1
should be
switched using software according to the operating clock.
High-speed operation voltage regulator
The high-speed operation voltage regulator generates the V
D3
voltage (2.0 V Typ.) for driving the
OSC3 oscillation circuit and the internal logic circuits in high-speed mode. Since this regulator stops
normally, turn it on using the VDC1 register (VDC1 = "1") and switch the internal logic operating
voltage to V
D3
using the VDC0 register before starting the OSC3 oscillation.
LCD system voltage circuit
The LCD system voltage circuit generates the LCD drive voltage. This circuit can be turned on and off
using the LPWR register. Turn this circuit on (LPWR = "1") before starting display on the LCD.
The LCD system voltage circuit generates V
C1
with the built-in voltage regulator, and generates two
other voltages (V
C2
= 2V
C1
, V
C3
= 3V
C1
) by boosting V
C1
. The V
C1
voltage value can be adjusted using
software in 16 steps (0.95 to 1.40 V). Refer to Section 4.8, "LCD Driver", for control of the V
C1
voltage
(contrast). This circuit does not operate when an external power supply is selected by mask option for
driving the LCD.
