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S1F76640 Series
2–60 EPSON S1F70000 Series
Technical Manual
Negative Voltage Conversion
S1F76640 can boost input voltage to negative power on the negative potential side by using the circuit shown in
Figure 8.6. (In case of 3 times step-up, remove the capacitor C
3 and the diode D4 and short-circuit the both ends of
D
4. In case of 2 times step-up, remove the capacitor C2 and the diode D3 and short-circuit the both ends of D3.) But
the output voltage drops by the forward voltage V
F of the diode. When GND is 0V, VDD is 5V and VF is 0.6V as
shown in Figure 8.6 for example, V
O is calculated as follows: VO = –15V–4 × 0.6V = –12.6V(In case of 3 times
step-up, V
O is calculated to –10V–3×0.6V = –8.2V, and in case of 2 times step-up, VO is calculated to –5V–2 × 0.6V
= –3.8V.)
Figure 8.6 Negative Voltage Conversion (Example of 3 times step-up circuit)
Negative Voltage Conversion + Positive Voltage Conversion
When the 3 times step-up operation shown in Figure 8.1 and the positive voltage conversion in Figure 8.6 are
combined, the circuit shown in Figure 8.7 can be formed and 20V and –12.6V can be obtained from the input 5V.
However, the output impedance is higher than in case of connection of either one only (the negative voltage conver-
sion or the positive voltage conversion).
Figure 8.7 Negative Voltage Conversion + Positive Voltage Conversion
RV
V
REG
TC1
TC2
P
OFF
V
SS
OSC1
OSC2
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
RI
V
O
CAP3+
CAP2+
CAP2–
CAP1+
CAP1–
V
DD
D
3
D
2
D
1
V
O
'
C
0
C
1
C
2
+
+
–
+
–
–
RV
V
REG
TC1
TC2
P
OFF
V
SS
OSC1
OSC2
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
RI
V
O
CAP3+
CAP2+
CAP2–
CAP1+
CAP1–
V
DD
V
O
'
V
O
'
+
–
+
+
–
+
–
+
–
–
+
–