Datasheet

Other Applications (Continued)
A three-stage cascade circuit shown in
Figure 7 generates −3V
in
, from V
in
.
Cascading is also possible when devices are operating in doubling mode. In
Figure 8 , two devices are cascaded to generate 3V
in
.
An example of using the circuit in
Figure 7 or Figure 8 is generating +15V or −15V from a +5V input.
Note that the number of n is practically limited since the increasing of n significantly reduces the efficiency and increases the out-
put resistance and output voltage ripple.
REGULATING V
out
It is possible to regulate the output of the MAX660 by use of a low dropout regulator (such as LP2951). The whole converter is
depicted in
Figure 9 . This converter can give a regulated output from −1.5V to −5.5V by choosing the proper resistor ratio:
where V
ref
=
1.235V.
DS100898-8
FIGURE 6. Increasing Output Voltage by Cascading Devices
DS100898-9
FIGURE 7. Generating −3V
in
from +V
in
DS100898-10
FIGURE 8. Generating +3V
in
from +V
in
MAX660
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