Datasheet

LM2765
SNVS070C –MARCH 2000–REVISED MAY 2013 www.ti.com
CASCADING DEVICES
Cascading the LM2765s is an easy way to produce a greater voltage (A two-stage cascade circuit is shown in
Figure 15).
The effective output resistance is equal to the weighted sum of each individual device:
R
out
= 1.5R
out_1
+ R
out_2
(5)
Note that increasing the number of cascading stages is pracitically limited since it significantly reduces the
efficiency, increases the output resistance and output voltage ripple.
Figure 15. Increasing Output Voltage by Cascading Devices
REGULATING V
OUT
It is possible to regulate the output of the LM2765 by use of a low dropout regulator (such as LP2980-5.0). The
whole converter is depicted in Figure 16.
A different output voltage is possible by use of LP2980-3.3, LP2980-3.0, or LP2980-adj.
Note that the following conditions must be satisfied simultaneously for worst case design:
2V
in_min
>V
out_min
+V
drop_max
(LP2980) + I
out_max
× R
out_max
(LM2765) (6)
2V
in_max
< V
out_max
+V
drop_min
(LP2980) + I
out_min
× R
out_min
(LM2765) (7)
Figure 16. Generate a Regulated +5V from +3V Input Voltage
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