Cascading Devices

Cascading the LM2665s is an easy way to produce a greater

voltage (A two-stage cascade circuit is shown in Figure 4).

The effective output resistance is equal to the weighted sum

of each individual device:

R

Note that, the increasing of the number of cascading stages

is pracitically limited since it significantly reduces the effi-

ciency, increases the output resistance and output voltage

ripple.

Regulating V

OUT

It is possible to regulate the output of the LM2665 by use of

a low dropout regulator (such as LP2980-5.0). The whole

converter is depicted in Figure 5.

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 simulta-

neously for worst case design:

2V

in_min

2V

DS100049-19

FIGURE 3. Lowering Output Resistance by Paralleling Devices

DS100049-20

FIGURE 4. Increasing Output Voltage by Cascading Devices

DS100049-21

FIGURE 5. Generate a Regulated +5V from +3V Input Voltage

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