REGULATING V

out

It is possible to regulate the output of the LM2660/LM2661 by use of a low dropout regulator (such as LP2951). The whole con-

verter is depicted in

Figure 8. This converter can give a regulated output from −1.5V to −5.5V by choosing the proper resistor ratio:

The error flag on pin 5 of the LP2951 goes low when the regulated output at pin 4 drops by about 5%. The LP2951 can be shut-

down by taking pin 3 high.

Also, as shown in

Figure 9 by operating LM2660/LM2661 in voltage doubling mode and adding a linear regulator (such as

LP2981) at the output, we can get +5V output from an input as low as +3V.

DS012911-27

FIGURE 8. Combining LM2660/LM2661 with LP2951 to Make a Negative Adjustable Regulator

DS012911-28

FIGURE 9. Generating +5V from +3V Input Voltage

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