Datasheet

LM2664
www.ti.com SNVS005D –NOVEMBER 1999–REVISED MAY 2013
Other Applications
PARALLELING DEVICES
Any number of LM2664s can be paralleled to reduce the output resistance. Each device must have its own
pumping capacitor C
1
, while only one output capacitor C
out
is needed as shown in Figure 16. The composite
output resistance is:
Figure 16. Lowering Output Resistance by Paralleling Devices
CASCADING DEVICES
Cascading the LM2664s is an easy way to produce a greater negative voltage (e.g. A two-stage cascade circuit
is shown in Figure 17).
If n is the integer representing the number of devices cascaded, the unloaded output voltage V
out
is (-nV
in
). The
effective output resistance is equal to the weighted sum of each individual device:
R
out
= nR
out_1
+ n/2 R
out_2
+ ... + R
out_n
(1)
Note that, the number of n is practically limited since the increasing of n significantly reduces the efficiency, and
increases the output resistance and output voltage ripple.
Figure 17. Increasing Output Voltage by Cascading Devices
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