S1C88348/317/316/308 TECHNICAL HARDWARE
EPSON
I-13
2 POWER SUPPLY
2 POWER SUPPLY
In this section, we will explain the operating
voltage and the configuration of the internal power
supply circuit of the S1C883xx.
2.1 Operating Voltage
The S1C883xx operating power voltage is as
follows:
Normal mode:
2.4 V to 5.5 V
Low power mode:
1.8 V to 3.5 V
High speed mode:
3.5 V to 5.5 V
If supply voltage drops below level 0 (see Chapter
7, "ELECTRICAL CHARACTERISTICS"), the
system is automatically reset by a supply voltage
detection (SVD) circuit described in the latter. This
function can be selected by mask option.
2.2 Internal Power Supply Circuit
The S1C883xx incorporate the power supply circuit
shown in Figure 2.2.1. When voltage within the
range described above is supplied to VDD (+) and
VSS (GND), all the voltage needed for the internal
circuit is generated internally in the IC.
Roughly speaking, the power supply circuit is
divided into two sections.
One section is the oscillation system voltage
regulator. The oscillation and internal circuits
operate on the voltage VD1, output by this circuit.
VD1 voltage can be selected from among three
types: 1.3 V (low-power mode), 2.2 V (normal
mode) and 3.3 V (high-speed mode).
It should be selected by a program to switch
according to the supply voltage and oscillation
frequency.
See Section 5.4, "Oscillation Circuits and Operating
Mode", for the switching of operating mode.
Note: Under no circumstances should VD1 terminal
output be used to drive external circuit.
The second circuit section is the power supply
circuit for the LCD system which generates the
drive voltage for the LCD. Drive voltage has five
potentials VC1–VC5 for 1/5 bias: VC1 and VC2 are
generated by the LCD voltage regulator, and are
boosted to generate VC3–VC5. These five potentials
are output externally at each of the terminals and
can be used to supply an external expanded LCD
driver.
See Chapter 7, "ELECTRICAL CHARACTERIS-
TICS" for the voltage values.
In the S1C883xx, the LCD drive voltage is supplied
to the built-in LCD driver which drives the LCD
panel connected to the SEG and COM terminals.
Note: Do not use terminals VC1–VC5 except to
supply voltage to the expanded LCD driver.
A load resistance between terminals VSS–
VC1 is needed when driving an LCD panel
that constitutes a heavy load.
Fig. 2.2.1
Configuration of
power supply circuit
VDD
VD1
VSS
Oscillation system
voltage regulater
LCD system
voltage regulater
LCD system
voltage booster
Oscillation circuit
Internal voltage
setting circuit
LCD driver
VD1
VC1, VC2
VC3–VC5
External
power
supply
Internal circuit
VC1
VC2
VC3
VC4
VC5
CA
CB
CC
CD
CE
OSC1–OSC4
COM0–COM15
COM16–COM31/SEG66–SEG51
SEG0–SEG50
COM0–COM15
COM16–COM31/SEG56–SEG41
SEG0–SEG40
S1C88348/317/316
S1C88308
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