
4 POWER SUPPLY
S1C17705 TECHNICAL MANUAL
Seiko Epson Corporation
4-1
Power Supply
4
Power Supply Voltage (V
4.1
DD
)
The operating voltage range of the S1C17705 is as follows:
For normal operation:
VDD = 1.8 V to 3.6 V (Normal operating mode)
For Flash programming: VDD = 2.7 V to 3.6 V (Flash erase/programming mode 1)
VDD = 2.5 V to 2.7 V (Flash erase/programming mode 2)
Supply a voltage within the range to the VDD pins with the VSS pins as the GND level. The S1C17705 provides two
or more VDD and VSS pins. Do not leave any power supply pins open and be sure to connect them to + power source
and GND.
Note: Do not use Flash erase/programming modes 1 and 2 for normal operation that does not perform
Flash erasing/programming.
Analog Power Supply Voltage (AV
4.2
DD
)
The analog power supply pin (AVDD) is provided separately from the VDD pin in order that the digital circuits do
not affect the analog circuits (A/D converter). The AVDD pin is used to supply an analog power voltage and the VSS
pin is used as the analog ground. The following voltage is enabled for AVDD:
AVDD = VDD = 1.8 V to 3.6 V (VSS = GND)
Note: Be sure to supply the same voltage as VDD to the AVDD pin even if the analog circuit is not used.
Noise on the analog power lines decrease the A/D converting precision, so use a stabilized power supply and make
the board pattern with consideration given to that.
Internal Power Supply Circuit
4.3
The S1C17705 has a built-in power supply circuit shown in Figure 4.3.1 to generate all the power voltages required
for the internal circuits. The power supply module consists of three circuits.
3.1 Power Supply Circuit
Table 4.
Circuit
Power supply circuit
Output voltage
Oscillator and internal logic circuits Internal logic voltage regulator
VDD or VD1
LCD system voltage regulator
Power voltage booster
VDD or VD2
LCD driver
LCD system voltage regulator
VC1 to VC5
Internal logic voltage regulator
The internal logic voltage regulator generates the VD1 operating voltage for the internal logic circuits and oscil-
lators. The VD1 voltage value can be switched in the program; set it to 1.8 V for normal operation and 2.5 V for
Flash programming.
Power voltage booster
The power voltage booster generates the VD2 operating voltage for the LCD system voltage regulator. Either
VDD or VD2 can be selected as the power source for the LCD system voltage regulator according to the VDD sup-
ply voltage value.
3.2 Power Source for LCD System Voltage Regulator
Table 4.
Power supply voltage VDD
Power source for the LCD system voltage regulator
1.8 to 2.5 V
VD2 (
@ VDD × 2)
2.5 to 3.6 V
VDD