S1F78100Y2A Epson Electronics America, Inc., S1F78100Y2A Datasheet - Page 172

• Manufacturer Part Number: S1F78100Y2A
• Description: High Precision Voltage Regulators
• Manufacturer: Epson Electronics America, Inc.

FUNCTIONAL DESCRIPTIONS
Basic Voltage Booster Operation
Tr1 switches ON and OFF at the frequency of the clock
pulses from the crystal oscillator. When the transistor is
ON, the circuit stores energy in L. When it is OFF, this
energy flows through D to charge C.
Internal Circuits
Crystal oscillator
The S1F76330 series incorporate a crystal oscillator cir-
cuit. An external crystal and drain resistor are used to
generate the booster circuit clock. The crystal oscillator
is connected to C
figure.
In the S1F76330 series, the crystal oscillator output is
sent to CL
lator circuit is activated by V
level is shifted and the output is connected to CL
oscillator output cannot be obtained without a voltage at
V
input voltage is applied, oscillation continues even in
standby mode.
Reference voltage generator and output
voltage regulator
The reference voltage generator regulates V
ate a voltage for the voltage regulator circuit.
S1F70000 Series
Technical Manual
O
. Since the crystal oscillator is activated when an
GND
V
I1
C
O
G
as the V
Crystal
C
D
I
and C
O
system signal. The crystal oscil-
L
R
D
O
as shown in the following
Tr1
C
I
C
O
but, because the output
I
D
S1F76330
C
I1
V
GND
to gener-
O
O
, the
EPSON
The output voltage regulator regulates the boosted out-
put voltage. This voltage is determined by the level at
point A between the two resistors connecting V
GND. These series use an on-chip resistor to set the
output at a specified voltage.
Note
In step-up voltage operation, the ripple voltage created
by the switching operation is large relative to the output
voltage described above. This ripple voltage is affected
by external components and load conditions. The user
is advised to check this voltage carefully.
Standby mode
Connecting PS to GND places the chip in standby
mode. In this mode, the crystal oscillator is disabled,
switching off the inductor drive transistor and the volt-
age booster circuit. Typically, PS is connected to RST.
If standby mode is not required, leave PS open as it has
a pull-up resistor.
Output voltage response compensation
The S1F76340 series incorporates a response compen-
sation input. A response compensation capacitor is
connected between V
voltage generated by the boosted output voltage to be
suppressed to a minimum.
Reference
generator
voltage
C
D
+
–
oscillator
CONT
Crystal
Crystal
and V
C
G
voltage regulator
S1F76300 Series
O
, allowing the ripple
A
Output
V
V
V
GND
I1
SW
O
O
4–27
and