I use two dc/dc regulator to generate 12V and 5V output from 40V input.
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.
Are you certain that your 40 to 12 converter will handle the additional current? If the 12 to 5 volt converter is 85% efficient, it will add about (5*1.5)/(0.8*12)=0.78 amps load , average, to the 12 volt output.
This one is about a dollar cheaper:
Here are a couple more possibilities:
-- Regards,
John Popelish
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
Dave.
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