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PDF MAX660 Data sheet ( Hoja de datos )
| Número de pieza | MAX660 | |
| Descripción | Switched Capacitor Voltage Converter | |
| Fabricantes | National Semiconductor | |
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November 1999
MAX660
Switched Capacitor Voltage Converter
General Description
The MAX660 CMOS charge-pump voltage converter inverts
a positive voltage in the range of 1.5V to 5.5V to the corre-
sponding negative voltage. The MAX660 uses two low cost
capacitors to provide 100 mA of output current without the
cost, size, and EMI related to inductor based converters.
With an operating current of only 120 µA and operating effi-
ciency greater than 90% at most loads, the MAX660 pro-
vides ideal performance for battery powered systems. The
MAX660 may also be used as a positive voltage doubler.
The oscillator frequency can be lowered by adding an exter-
nal capacitor to the OSC pin. Also, the OSC pin may be used
to drive the MAX660 with an external clock. A frequency con-
trol (FC) pin selects the oscillator frequency of 10 kHz or 80
kHz.
Features
n Inverts or doubles input supply voltage
n Narrow SO-8 Package
n 6.5Ω typical output resistance
n 88% typical conversion efficiency at 100 mA
n Selectable oscillator frequency: 10 kHz/80 kHz
Applications
n Laptop computers
n Cellular phones
n Medical instruments
n Operational amplifier power supplies
n Interface power supplies
n Handheld instruments
Typical Application Circuits
Voltage Inverter
Positive Voltage Doubler
Connection Diagram
DS100898-1
8-Lead SO
DS100898-2
Ordering Information
Order Number
MAX660M
MAX660MX
Top Mark
Date Code
MAX660M
Date Code
MAX660M
DS100898-5
Top View
Package
M08A
M08A
Supplied as
Rail (95 units/rail)
Tape and Reel (2500 units/rail)
© 1999 National Semiconductor Corporation DS100898
www.national.com
1 page  
Pin Description
Pin Name
Function
Voltage Inverter
Voltage Doubler
1 FC Frequency control for internal oscillator:
Same as inverter.
FC = open, fOSC = 10 kHz (typ);
FC = V+, fOSC = 80 kHz (typ);
FC has no effect when OSC pin is driven externally.
2
CAP+
Connect this pin to the positive terminal of
charge-pump capacitor.
Same as inverter.
3
GND
Power supply ground input.
Power supply positive voltage input.
4
CAP−
Connect this pin to the negative terminal of
charge-pump capacitor.
Same as inverter.
5
OUT
Negative voltage output.
Power supply ground input.
6 LV Low-voltage operation input. Tie LV to GND when LV must be tied to OUT.
input voltage is less than 3.5V. Above 3.5V, LV can
be connected to GND or left open. When driving
OSC with an external clock, LV must be connected
to GND.
7
OSC
Oscillator control input. OSC is connected to an
Same as inverter except that OSC cannot be driven
internal 15 pF capacitor. An external capacitor can
by an external clock.
be connected to slow the oscillator. Also, an
external clock can be used to drive OSC.
8 V+ Power supply positive voltage input.
Positive voltage output.
Circuit Description
The MAX660 contains four large CMOS switches which are
switched in a sequence to invert the input supply voltage.
Energy transfer and storage are provided by external capaci-
tors. Figure 2 illustrates the voltage conversion scheme.
When S1 and S3 are closed, C1 charges to the supply volt-
age V+. During this time interval switches S2 and S4 are
open. In the second time interval, S1 and S3 are open and S2
and S4 are closed, C1 is charging C2. After a number of
cycles, the voltage across C2 will be pumped to V+. Since
the anode of C2 is connected to ground, the output at the
cathode of C2 equals −(V+) assuming no load on C2, no loss
in the switches, and no ESR in the capacitors. In reality, the
charge transfer efficiency depends on the switching fre-
quency, the on-resistance of the switches, and the ESR of
the capacitors.
Application Information
SIMPLE NEGATIVE VOLTAGE CONVERTER
The main application of MAX660 is to generate a negative
supply voltage. The voltage inverter circuit uses only two ex-
ternal capacitors as shown in the Typical Application Circuits.
The range of the input supply voltage is 1.5V to 5.5V. For a
supply voltage less than 3.5V, the LV pin must be connected
to ground to bypass the internal regulator circuitry. This gives
the best performance in low voltage applications. If the sup-
ply voltage is greater than 3.5V, LV may be connected to
ground or left open. The choice of leaving LV open simplifies
the direct substitution of the MAX660 for the LMC7660
Switched Capacitor Voltage Converter.
The output characteristics of this circuit can be approximated
by an ideal voltage source in series with a resistor. The volt-
age source equals −(V+). The output resistance Rout is a
function of the ON resistance of the internal MOS switches,
the oscillator frequency, and the capacitance and ESR of C1
and C2. A good approximation is:
DS100898-21
FIGURE 2. Voltage Inverting Principle
where RSW is the sum of the ON resistance of the internal
MOS switches shown in Figure 2.
High value, low ESR capacitors will reduce the output resis-
tance. Instead of increasing the capacitance, the oscillator
frequency can be increased to reduce the 2/(fosc x C1) term.
Once this term is trivial compared with RSW and ESRs, fur-
ther increasing in oscillator frequency and capacitance will
become ineffective.
The peak-to-peak output voltage ripple is determined by the
oscillator frequency, and the capacitance and ESR of the
output capacitor C2:
5 www.national.com
5 Page 
Physical Dimensions inches (millimeters) unless otherwise noted
8-Lead SO (M)
Order Number MAX660M
NS Package Number M08A
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
National Semiconductor
Corporation
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: [email protected]
www.national.com
National Semiconductor
Europe
Fax: +49 (0) 1 80-530 85 86
Email: [email protected]
Deutsch Tel: +49 (0) 1 80-530 85 85
English Tel: +49 (0) 1 80-532 78 32
Français Tel: +49 (0) 1 80-532 93 58
Italiano Tel: +49 (0) 1 80-534 16 80
National Semiconductor
Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
Email: [email protected]
National Semiconductor
Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
11 Page | ||
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| PDF Descargar | [ Datasheet MAX660.PDF ] | |
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