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Date: 3/6/06

SP6656, 400mA Synchronous Buck Regulator with Dynamically Adjustable Voltage Output

© Copyright 2006 Sipex Corporation

The output voltage is programmed by the external divider, as shown in the typical

application circuit on Page 1. Depending on the topology used, 1 or 2 voltages ,V

OUT

is set as follows:

APPLICATION INFORMATION

1) Single V

OUT

First pick a value for RI that is no larger than

300KΩ. Too large a value of RI will reduce the

AC voltage seen by the loop comparator since

the internal FB pin capacitance can form a low

pass filter with RF in parallel with RI. The

formula for RF with a given RI and output

voltage is:

2) Dual V

First pick the lowest voltage that will be used

and utilize the same method as above.

Then use the following equation to determine

VO

FB

OVSO

CF

22pF

VO

FB

CF

22pF

.

1 -

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