Page 1
1.
DC/DC Converter
Page 2
SCI7660 Series
DESCRIPTION
The SCI7660 Series is a highly efficient CMOS DC/DC
converter for doubling an input voltage. This powersaving IC allows portable computers and similar handheld equipment to operate from a single power supply,
even when they incorporate LSIs that operate at voltages different from those of logic circuits, for example,
LCD drivers and analog LSIs.
The SCI7660C
the SCI7660M
0B is available in 8-pin plastic DIPs, and
0B, in 8-pin plastic SOPs.
FEATURES
• 95% (typ.) conversion efficiency
• Two output voltages, VO, relative to VDD and VI
• 30mA maximum output current at 5V
• Two-in-series configuration doubles negative output
voltage.
• Low operating voltage
• On-chip RC oscillator
• 8-pin plastic DIP and 8-pin plastic SOP
APPLICATIONS
• Fixed-voltage power supplies for battery-operated
equipment
• Power supplies for pagers, memory cards, calculators
and similar hand-held equipment
• Fixed-voltage power supplies for medical equipment
• Fixed-voltage power supplies for communications
equipment
• Uninterruptable power supplies
BLOCK DIAGRAM
V
DD
OSC1
OSC2
V
I
RC oscillator
Voltage converter
PIN CONFIGURATION
1
NC
2
OSC2
OSC1
DD
V
SCI7660C
3
4
DC/DC
Converter
CAP1+
CAP1–
V
O
8
V
I
V
O
7
0B
CAP1–
6
CAP1+
5
PIN DESCRIPTION
Number Name Description
1 NC No connection
2 OSC2 Resistor connection. Open when using external clock
3 OSC1 Resistor connection. Clock input when using external clock
4VDD Positive supply (system VCC)
5 CAP1+ Positive charge-pump connection
6 CAP1– Negative charge-pump connection
7VO ×2 multiplier output
8VI Negative supply (system ground)
SCI7000 Series EPSON 1–1
Technical Manual
Page 3
SCI7660 Series
SPECIFICATIONS
Absolute Maximum Ratings
Parameter Symbol Rating Unit
Input voltage range VI –10.0 to 0.5 V
Output voltage range VO Min. –20.0 V
Power dissipation PD
300 (DIP)
150 (SOP)
Operating temperature range Topr –40 to 85 ˚C
Storage temperature range
Soldering temperature(for 10s). See note.
Tstg –65 to 150 ˚C
Tsol 260 ˚C
Note:
Temperatures during reflow soldering must remain within the limits set out in LSI Device Precautions.
Never use solder dip to mount SCI7000 series power supply devices.
Recommended Operating Conditions
DD = 0V, Ta = –40 to 85˚C unless otherwise noted
V
Rating
Parameter Symbol Condition
Min. Typ. Max.
ROSC = 1MΩ,
C1/C2≤1/20, C2≥10µF, — — –1.5
Oscillator startup voltage V
STA Ta = –40 to 85˚C V
See note 1.
ROSC = 1MΩ — — –2.2
Oscillator shutdown voltage
Load resistance RL
VSTP ROSC = 1MΩ –1.5 — — V
RL min
See note 2.
——Ω
Output current IO — — 30.0 mA
Clock frequency fOSC 10.0 — 30.0 kHz
RC oscillator network
resistance
R
OSC 680 — 2,000 kΩ
Capacitance C1, C2 3.3 — — µF
Notes:
1. The recommended circuit configuration for low-voltage operation (when V
I is between –1.2V and
–2.2V) is shown in the following figure. Note that diode D1 should have a maximum forward voltage of
0.6V with 1.0mA forward current.
L min can be varied depending on the input voltage.
2. R
mW
Unit
1–2 EPSON SCI7000 Series
Technical Manual
Page 4
SCI7660 Series
1MΩ
Battery
1
2
3
4
8
+
C2
22µF
7
6
C1
+
10µF
5
R
C
L
L
D1
3. RL min is a function of VI.
5
4
V
STA1
3
2
1
Minimum load resistance (kΩ)
0
1.0
1.5 2.0
STA2
V
Input voltage (V)
3.0
4.0 5.0 6.0
Electrical Characteristics
VDD = 0V, Ta = –40 to 85˚C unless otherwise noted
Rating
Parameter Symbol Condition
Min. Typ. Max.
Input voltage VI –8.0 — –1.5 V
Output voltage VO –16.0 — — V
Multiplier current Iopr
RL = ∞, ROSC = 1MΩ
I = –5V
V
—2030µA
Quiescent current IQ RL =∞, VI = –8V — — 2.0 µA
Clock frequency fOSC
ROSC = 1MΩ, VI = –5V
16 20 24 kHz
Output impedance RO IO = 10mA, VI = –5V — 75 100 Ω
Multiplication efficiency Peff IO = 5mA, VI = –5V 90 95 — %
OSC1 Input leakage current
ILKI VI = –8V — — 2.0 µA
Unit
DC/DC
Converter
SCI7000 Series EPSON 1–3
Technical Manual
Page 5
SCI7660 Series
Typical Performance Characteristics
1000
Ta = 25°C
26
25
24
23
22
21
20
19
18
[KHz]
17
16
OSC
f
15
14
13
VI = –5.0V
I
= –3.0V
V
I
= –2.0V
V
100
[KHz]
OSC
f
10
I
= –5V
V
VI = –3V
VI = –2V
12
11
10
9
1
10 100 1000 10000
R
OSC
[kΩ]
8
–40 –20 0 20 40
Ta [°C]
60 80 100
Clock frequency vs. External resistance Clock frequency vs. Ambient temperature
50
f
OSC
OSC
f
20kHz
f
OSC
10kHz
= 40kHz
Ta = 25°C
=
=
45
40
35
30
[µA]
25
@lopr
20
15
10
5
0
–7 –6 –5 –4 –3 –2 –1 0
VI [V]
0
Ta = 25
I
= –5.0V
V
–5
[V]
O
V
–10
–15
0 1020304050
IO [mA]
Multiplier current vs. Input voltage Output voltage vs. Output current
1–4 EPSON SCI7000 Series
Technical Manual
Page 6
SCI7660 Series
0
Ta = 25°C
I
= –3.0V
V
0
–1
Ta = 25°C
V
I
= –2.0V
–2
[V]
–3
[V]
O
V
–5
O
V
–4
–5
–10
0102030
IO [mA]
–6
0 23456789101
IO [mA]
Output voltage vs. Output current Output voltage vs. Output current
300
Ta = 25°C
I
O = 7mA
200
RO [Ω]
300
Ta = 25°C
I
o
= 10mA
200
[Ω]
O
R
DC/DC
Converter
100
0
–7 –6 –5 –4 –3 –2 –1 0
VI [V]
100
0
–7 –6 –5 –4 –3 –2 –1 0
VI [V]
Output impedance vs. Input voltage Output impedance vs. Input voltage
SCI7000 Series EPSON 1–5
Technical Manual
Page 7
SCI7660 Series
100
IO = 2mA
IO = 5mA
90
IO = 10mA
80
70
60
IO = 20mA
IO = 30mA
50
Peff [%]
40
30
20
VI = –5.0V
10
0
1 10 100 1000
f
OSC
[kHz]
100
IO = 0.5mA
IO = 1.0mA
90
IO = 2.0mA
IO = 4.0mA
80
70
60
50
Peff [%]
40
30
20
VI = –3.0V
10
0
1 10 100 1000
fOSC [kHz]
Multiplication efficiency vs. Clock frequency Multiplication efficiency vs. Clock frequency
100
90
80
70
60
50
Peff [%]
40
30
20
10
0
Ta = 25°C
V
I
= –5.0V
0
10 20 30 40 50
IO [mA]
Peff
100
I
I
90
80
70
60
50
40
30
20
10
0
[mA]
I
I
100
90
80
70
Ta = 25°C
60
V
I
= –3.0V
50
40
Peff [%]
30
20
10
0
0 5 10 15 20 25 30
I
I
Peff
100
90
80
70
60
50
40
30
20
10
0
IO [mA]
[mA]
I
I
Multiplication efficiency/input current vs. Multiplication efficiency/input current vs.
Output current Output current
1–6 EPSON SCI7000 Series
Technical Manual
Page 8
SCI7660 Series
100
90
80
70
Ta = 25°C
VI = –2.0V
60
50
Peff [%]
40
30
20
10
0
012345678910
IO [mA]
Peff
40
36
32
28
24
20
II
16
12
8
4
0
Multiplication efficiency/input current vs.
Output current
FUNCTIONAL DESCRIPTION
RC Oscillator
The on-chip RC oscillator network frequency is determined by the external resistor, ROSC, connected between OSC1 and OSC2. This oscillator can be disabled
in favor of an external clock by leaving OSC2 open and
applying an external clock signal to OSC1.
I [mA]
I
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, between CAP1+ and CAP1–, and a smoothing capacitor,
C2, between V
I and VO.
DC/DC
Converter
Oscillator External clock
OSC1
OSC2
OSC1
OSC
R
OSC2
External clock
signal
V
= –5 V
I
1MΩ
= 0 V
V
DD
5 V
1
2
3
4
8
+
C2
10µF
7
V
= –10V (2VI)
O1
6
C1
+
10µF
5
Doubled potential levels
V
CC
(+5V)
GND
(–5V)
SCI7000 Series EPSON 1–7
Technical Manual
DD
= 0 V
V
I
= –5 V
V
VO = (2VI) = –10 V
Page 9
SCI7660 Series
TYPICAL APPLICATIONS
Parallel Connection
Connecting two or more chips in parallel reduces the
output impedance by 1/n, where n is the number of devices used.
V
= 0 V
DD
= –5 V
5 V
V
I
8
+
C2
10µF
7
6
C1
+
10µF
5
1MΩ
1
2
3
4
Serial Connection
Connecting two or more chips in series obtains a higher
output voltage than can be obtained using a parallel
V
= 0 V
DD
5 V
= –5 V
V
I
8
+
C2
10µF
7
6
C1
+
10µF
5
= –10 V = VI'
V
O
1MΩ
1
2
3
4
8
7
6
C1
+
10µF
5
V
= –10 V
O
1MΩ
1
2
3
4
connection, however, this also raises the output impedance.
V
' = VI = –5
DD
8
+
C2
10µF
7
6
C1
+
10µF
5
' = –15 V
V
O
1MΩ
1
2
3
4
Potential levels
V
DD
(0 V)
I
(–5 V)
V
O
(–10 V)
V
Primary stage Secondary stage
V
DD
V
I
VO (–15 V)
1–8 EPSON SCI7000 Series
Technical Manual
Page 10
Positive Voltage Conversion
VO2 = 3.8 V
V
O1 = –10 V
V
DD = 0 V
V
I= –5 V
Diodes can be added to a circuit connected in parallel to
make a negative voltage positive.
V
= 0 V
DD
5 V
= –5 V
V
I
1MΩ
1
2
3
4
8
7
6
5
V
Simultaneous Voltage Conversion
Combining a multiplier circuit with a positive voltage
conversion circuit generates both –10 and 3.8 V outputs
from a single input.
' = 3.8 V
O
C2
+
10µF
C1
+
10µF
Potential levels
SCI7660 Series
DC/DC
Converter
VDD = 0 V
= –5 V
5 V
= 3.8 V
V
O2
C2
10µF
V
O1
C1
10µF
C4
10µF
= –10 V
C3
10µF
++
+
1
2
3
4
8
7
6
+
5
V
I
1MΩ
SCI7000 Series EPSON 1–9
Technical Manual
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