Functional descriptions, Epson, Voltage multiplier – Epson Power Supply S1F70000 User Manual
Page 24
S1F76600 Series
S1F70000 Series
EPSON
1–7
Technical Manual
S1F76600
Series
FUNCTIONAL DESCRIPTIONS
CR Oscillator
S1F76600 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
100
90
80
70
60
50
40
30
20
10
0
40
36
32
28
24
20
16
12
8
4
0
0
1
2
3
4
5
6
7
8
9
10
P
eff [%]
I
I
[mA]
I
O
[mA]
Ta = 25
°
C
V
I
= –2.0V
I
I
Peff
(13) Multiplication efficiency/input current
vs. Output current
Voltage Multiplier
The voltage multiplier uses the clock signal from the
oscillator to double the input voltage. This requires two
external capacitors—a charge-pump capacitor, C1, be-
tween CAP1+ and CAP1–, and a smoothing capacitor,
C2, between V
I
and V
O
.
5 V
C1
10
µ
F
C2
10
µ
F
V
O1
= –10V (2V
I
)
V
DD
= 0 V
V
I
= –5 V
1M
Ω
+
+
8
7
6
5
1
2
3
4
Doubled potential levels
V
CC
(+5V)
(–5V)
GND
V
O
= (2V
I
)
= –10 V
V
I
= –5 V
V
DD
= 0 V
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