5. DESCRIPTION OF BLOCK DIAGRAM
S1F76980 Technical Manual (Rev.1.0)
EPSON
3
5. DESCRIPTION OF BLOCK DIAGRAM
(1) Power voltage monitoring circuit (V
CC
, V
BUS
, V
BAT
)
This circuit monitors input voltage of each power supply pin and detects low voltage. Leaving hysteresis width
prevents output from becoming unstable (oscillating) when low voltage is detected.
Moreover, the IC contains a circuit to guarantee the voltage monitoring result below the operating voltage.
(2) Power switching circuit
This circuit selects a power supply (V
DD
) used in the IC from three power supplies (V
CC
, V
BUS
and V
BAT
).
(3) Reference voltage generator
This circuit generates reference voltage and reference current necessary in this IC.
(4) Power-on reset circuit
This circuit generates IC initialization signal until the internal power supply of the IC (V
DD
) is recharged.
(5) Switching control circuit
This circuit controls output of a signal that selects optimum input power supply according to input conditions of
three power supplies (V
CC
, V
BUS
, and V
BAT
) and in the priority sequence set in the IC. The priority sequence of
V
BUS
and V
BAT
can also be switched during operation, using the external pin BSEL.
