Epson S1F70000 User Manual

S1F70000 Series

1–13

Technical Manual

S1F76620 has a built-in CR oscillator as the internal os-
cillator, and an external oscillation resistor R

OSC

 is con-

nected between the pins OSC1 and OSC2 before opera-
tion.

 

OSC1

OSC2

R

OSC

 (Note 1)

Note 1
Since the oscillation frequency varies with wiring ca-
pacitance, make the cables between the terminals OSC1
and OSC2 and R

OSC

 as short as possible.

When setting the external resistor R

OSC

, find R

OSC

 suit-

able for f

OSC

 that brings about the maximum efficiency

from characteristics graph (9) and (10).  The relations
between R

OSC

 and f

OSC

 in characteristics graph (1) are

expressed approximately with the following formula as
far as the
straight portion (500k

Ω

 < R

OSC

 < 2M

Ω

) is concerned:

R

OSC

 = A • (1/f

OSC

)

(A : Constant, When GND is 0V and V

DD

 is 5V, A is

approximately 2.0 

×

 10

10

 (I/F).)

So, the R

OSC

 value can be obtained from this formula.

(Recommended oscillation frequency : 10kHz to 30kHz
(R

OSC

 : 2M

Ω

 to 680k

Ω

))

When the external clock operates, make the pin OSC2
open as shown below and input the 50% duty of the ex-

ternal clock from the pin OSC1.

OSC1

OSC2

External clock

Open

The voltage conversion circuit uses clocks generated in
the CR oscillator to double the input supply voltage
V

DD

.

In case of 2 times step-up, 2 times voltage  (2V

DD

) of

the input voltage is obtained from the V

O

 pin when a

pump up capacitor is connected between CAP1+ and
CAP2– and a smoothing capacitor is connected be-
tween V

DD

 and V

O

 outside.

When GND is 0 and V

DD

 is 5, the relations between

input/output and voltage are as shown below:

CAP1=2V

DD

=10V

V

DD

=5V

G

ND

=0V