Power Supply User Manual

S1F78100Y Series
S1F70000 Series EPSON 3–3
Technical Manual
S1F78100Y
Series
FUNCTIONAL DESCRIPTIONS
S1F78100Y Series is a fixed positive output type volt-
age regulator of series regulator system and is fitted
with an output control MOS transistor between the in-
put and output pins as shown in the figure below. The
voltage regulator feeds back voltages (V
REG) divided
with the built-in resistors R
1 and R2 connected between
V DD
(2pin)
V
SS
(1pin)
V
O
(3pin)
R2
R1
V
REF
+
–
(V
REG )
(Output control transistor)
(Operational amplifier)
the output pin (VO pin) and the VSS pin to compare
them with the reference voltage (V
REF) and outputs the
stable output voltage (V
0) not depending on input volt-
age by controlling the gate voltage of the output control
transistor. The output voltage is fixed inside and is de-
cided with the following formula:
V
O =
R1+R2
·VREF
R1