Datasheet

LM2664
SNVS005D –NOVEMBER 1999–REVISED MAY 2013 www.ti.com
COMBINED DOUBLER AND INVERTER
In Figure 18, the LM2664 is used to provide a positive voltage doubler and a negative voltage converter. Note
that the total current drawn from the two outputs should not exceed 50 mA.
Figure 18. Combined Voltage Doubler and Inverter
REGULATING V
OUT
It is possible to regulate the negative output of the LM2664 by use of a low dropout regulator (such as LP2980).
The whole converter is depicted in Figure 19. This converter can give a regulated output from −1.8V to −5.5V by
choosing the proper resistor ratio:
V
out
= V
ref
(1 + R
1
/R
2
) (2)
where, V
ref
= 1.23V (3)
Note that, the following conditions must be satisfied simultaneously for worst case design:
V
in_min
>V
out_min
+V
drop_max
(LP2980) (4)
+ I
out_max
× R
out_max
(LM2664) (5)
V
in_max
< V
out_max
+V
drop_min
(LP2980) (6)
+ I
out_min
× R
out_min
(LM2664) (7)
Figure 19. Combining LM2664 with LP2980 to Make a Negative Adjustable Regulator
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