Tool/software: WEBENCH® Design Tools
Dear all.
Please teach me about difference from WEBENCH and the calculation.
In the case of IN=24V, OUT=3.3V/0.7A, it becomes 29uH when I calculate in Equation 8 of the datasheet.
But, it becomes 7.8uH by the result of WEBENCH.
This is the minimum value of the output inductor (LMIN).
Why will it become the value smaller than LMIN in WEBENCH?
Whitch is best?
Regards,
PAN-M
Hi PAN,
Inductor calculation in data sheet considers 35% of ripple current and that’s why the value is 29uH.This leads to lesser peak current as shown in below image.
Operating values with 29 uH inductor( peak current, ripple, efficiency, duty, etc)
In Webench inductor is designed by using 140% of ripple current for this condition that’s why the value is 7.8uH. This leads to higher peak current as shown in below image.
Operating values with 7.8 uH inductor( peak current, ripple, efficiency, duty, etc)
Since the load current is smaller i.e 0.7A it can be ok to choose Webench design which will give little higher peak current(~1.2 A) with 7.8 uH inductor as compared to using 29 uH inductor with lower peak current(~0.8 A).
Best Regards,
Mahantesh
