Epson S1F70000 User Manual

S1F70000 Series

2–43

Technical Manual

     S1F76640 has a built-in CR oscillator as the internal oscillator, and an external oscillation resistor R

OSC

 is

connected between the pins OSC1 and OSC2 before operation. (Figure 5.1)

Note 1 :

Since the oscillation frequency varies with wiring capacitance, make the cables between the terminals
OSC1 and OSC2 and R

OSC

 as short as possible.

   When setting the external resistor R

OSC

, find the oscillation frequency f

OSC

 that brings about the maximum effi-

ciency from Figures 6.5.12 and 6.5.13 and find R

OSC

 suitable for the f

OSC

 from Figure 6.5.1   The relations between

R

OSC

 and f

OSC

 in Figure 6.5.1 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

   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 in Figure 5.2 and input the 50% duty of the
external clock from the pin OSC1.

     The voltage conversion circuits (I) and (II) doubles and triples the input voltage V

DD

 respectively by using clock

generated in the CR oscillator.
   In case of 2 times step-up, 2 times step-up output of the input voltage is obtained from the V

O

 pin when a pump up

capacitor is connected between CAP1+ and CAP1–, CAP2+ and CAP3+ are short-circuited to V

O

 and a smoothing

capacitor is connected between V

DD

 and V

O

 outside.

   In case of 3 times step-up, 3 V

DD

 is output from the V

O

 pin when a pump up capacitor is connected between

CAP1+ and CAP1– and between CAP2+ and CAP2– respectively and a smoothing capacitor is connected between
the V

DD

 and V

O

 pins outside.

   In case of 4 times step-up, 4 V

DD

 is output from the V

O

 pin when a pump up capacitor is connected between

CAP1+ and CAP1–, between CAP2+ and CAP2– and between CAP1+ and CAP3– respectively and a smoothing
capacitor is connected between the V

DD

 and V

O

 pins outside.

   When GND is 0 and V

DD

 is 5, the relations between the input voltage and the output voltage are as shown in

Figures 5-3, 5-4 and 5-5.

OSC1

OSC2

OSC1

OSC2

Open

External clock

(Note 1)

R

OSC

A : Constant, When GND is 0V and
V

DD

 is 5V, A is 2.0

×

10

10

 (1/F).)

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