SWITCHED CAPACITOR
VOLTAGE CONVERTER
SC1660
January 30, 1998
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, TA = 25°C, V+ = 5V, OSC = free running
Parameter
Symbol
Conditions
Min
Input Voltage
V+
RL=∞
1.5
Supply Current
Output Resistance
IS
ROUT
RL=∞
IL=20mA, fOSC = 10kHz
Oscillator Frequency
fOSC
Pin 1=V+
RL=∞
Efficiency
η
RL = 5K, fOSC = 10kHz
96
Voltage Conversion
Efficiency
ηVOUT
RL=∞
98
Typ
35
45
10
50
98
99.9
Max
9
70
90
Units
V
µA
Ω
kHz
%
%
TYPICAL APPLICATIONS
• Negative Voltage Converter
Figure 1 shows a typical connection which will
provide a negative supply from an available posi-
tive supply without the need for any external
diodes. The LV pin should be connected to ground
for V+ ≤ 3V; for V+ > 3V it may be left floating.
• Voltage Doubling
Figure 2 shows a method of voltage doubling.
Doubling is achieved by simply rearranging the
connection of the two external capacitors. An
external 500kΩ resistor is required to ensure the
oscillator will start.
• Ultra Precision Voltage Divider
An ultra precision voltage divider is shown in Fig-
ure 3. To achieve the 0.0002% accuracy indicated,
the load current should be kept below 100nA.
However, with a slight loss in accuracy, the load
current can be increased.
• Battery Splitter
A common need in many systems is to obtain
positive and negative supplies from a single battery
or power supply system. Where current require-
ments are small, the circuit shown in Figure 4 is a
simple solution.
© 1997 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320