cascading two dc/dc regulator

[Chris Lee]

I use two dc/dc regulator to generate 12V and 5V output from 40V
input.

40V --- LM5576 --- 12V

40V --- LM5576 --- 5V

Since LM5576 is too expensive, I wonder if I can use a cheaper dc/dc
converter in cascade with LM5576 to generate 5V from 12V as the
following?
I can not use a LDO for 12V to 5V because the loading is about 1.5A,
the board will get too hot.

40V --- LM5576 --- 12V --- AT1796 --- 5V

 

[[email protected]]

http://search.digikey.com/scripts/DkSearch/dksus.dll?PName?Name=296-19671-5-ND

 

[David L. Jones]

I use two dc/dc regulator to generate 12V and 5V output from 40V
input.

40V --- LM5576 --- 12V

40V --- LM5576 --- 5V

Since LM5576 is too expensive, I wonder if I can use a cheaper dc/dc
converter in cascade with LM5576 to generate 5V from 12V as the
following?
I can not use a LDO for 12V to 5V because the loading is about 1.5A,
the board will get too hot.

40V --- LM5576 --- 12V --- AT1796 --- 5V

Yes, you can do that, provided your LM5576 can handle the new total
load including inefficiencies.

There are squillions of regulators, so there are most likely cheaper
options available.
Pick some parts you like and use http://www.findchips.com/ to compare
prices and availability.

Dave.