2 POWER SUPPLY, RESET, AND CLOCKS
S1C17M20/M21/M22/M23/M24/M25
Seiko Epson Corporation
2-1
TECHNICAL MANUAL (Rev. 1.0)
2 Power Supply, Reset, and Clocks
The power supply, reset, and clocks in this IC are managed by the embedded power generator, system reset control-
ler, and clock generator, respectively.
2.1 Power Generator (PWG)
2.1.1 Overview
PWG is the power generator that controls the internal power supply system to drive this IC with stability and low
power. The main features of PWG are outlined below.
• Embedded V
D1
regulator
- The V
D1
regulator generates the V
D1
voltage to drive internal circuits, this makes it possible to keep current
consumption constant independent of the V
DD
voltage level.
- The V
D1
regulator supports two operation modes, normal mode and economy mode, and setting the V
D1
regu-
lator into economy mode at light loads helps achieve low-power operations.
Figure 2.1.1.1 shows the PWG configuration.
PWG
Internal circuits
V
D1
regulator
V
DD
V
D1
V
D1
V
SS
C
PW1
C
PW2
+
REGMODE[1:0]
Figure 2.1.1.1 PWG Configuration
2.1.2 Pins
Table 2.1.2.1 lists the PWG pins.
Table 2.1.2.1 List of PWG Pins
Pin name
I/O
Initial status
Function
V
DD
P
–
Power supply (+)
V
SS
P
–
GND
V
D1
A
–
Embedded regulator output pin
For the V
DD
operating voltage range and recommended external parts, refer to “Recommended Operating Condi-
tions, Power supply voltage V
DD
” in the “Electrical Characteristics” chapter and the “Basic External Connection
Diagram” chapter, respectively.
2.1.3 V
D1
Regulator Operation Mode
The V
D1
regulator supports two operation modes, normal mode and economy mode. Setting the V
D1
regulator into
economy mode at light loads helps achieve low-power operations. Table 2.1.3.1 lists examples of light load condi-
tions in which economy mode can be set.
Table 2.1.3.1 Examples of Light Load Conditions in which Economy Mode Can be Set
Light load condition
Exceptions
SLEEP mode (when all oscillators are stopped, or OSC1 only is active) When a clock source except for OSC1 is
active
HALT mode (when OSC1 only is active)
RUN mode (when OSC1 only is active)
The V
D1
regulator also supports automatic mode in which the hardware detects a light load condition and automati-
cally switches between normal mode and economy mode. Use the V
D1
regulator in automatic mode when no special
control is required.