© 1997 SEMTECH CORP.

652 MITCHELL ROAD NEWBURY PARK CA 91320

SWITCHED CAPACITOR

VOLTAGE CONVERTER

SC1660

January 30, 1998

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, T

Parameter

Symbol

Conditions

Min

Typ

Max

Units

Input Voltage

V

+

R

1.5

9

V

Supply Current

I

S

R

35

70

µA

Output Resistance

R

OUT

I

45

90

Ω

Oscillator Frequency

Pin 1=V

+

f

OSC

R

10

50

kHz

Efficiency

η

R

96

98

%

Voltage Conversion

Efficiency

η

R

98

99.9

%

TYPICAL APPLICATIONS

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

+

Figure 2 shows a method of voltage doubling.

Doubling is achieved by simply rearranging the

connection of the two external capacitors. An

external 500k

Ω resistor is required to ensure the

oscillator will start.

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.

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.