Step-up DC-DC converter


LT1110 based design.  
4 to 6 volt input
8 volt output

Design equations are from the datasheet.

[Graphics:Images/dc2dc_r1_gr_1.gif]


Vout setting
(resistor selection)

[Graphics:Images/dc2dc_r1_gr_2.gif]
[Graphics:Images/dc2dc_r1_gr_3.gif]

use 348K + 5.61K in series

Then linear regulate back to 5V.
The linear regulation reduces the switching ripple to a level that is within the receiver's specification.


Inductor selection

Power required from inductor:

[Graphics:Images/dc2dc_r1_gr_4.gif]
[Graphics:Images/dc2dc_r1_gr_5.gif]
[Graphics:Images/dc2dc_r1_gr_6.gif]

Inductor energy

[Graphics:Images/dc2dc_r1_gr_7.gif]
[Graphics:Images/dc2dc_r1_gr_8.gif]

Current in inductor

[Graphics:Images/dc2dc_r1_gr_9.gif]
[Graphics:Images/dc2dc_r1_gr_10.gif]
[Graphics:Images/dc2dc_r1_gr_11.gif]
[Graphics:Images/dc2dc_r1_gr_12.gif]
[Graphics:Images/dc2dc_r1_gr_13.gif]

Energy in inductor

[Graphics:Images/dc2dc_r1_gr_14.gif]
[Graphics:Images/dc2dc_r1_gr_15.gif]

which is more than the 1.6 uJ required, so this is an OK selection


| © 2005 Ken Staton
Converted by Mathematica      January 12, 2002