Tool/software: WEBENCH® Design Tools
Hello,
I am confused about what I think are some discrepancies in the design Webench is suggesting and what I believe the datasheet is indicating I should do.
I am using the LMR36015-Q1 to convert 36V to 5V. The max load I'd like the converter to handle is 0.8A, however, nominal load will be pretty light probably between 0.2 - 0.3A.
My concern regards the input capacitors and Cboot.
Webench is suggesting the following:
However the datasheet says the following:
1. Values listed for the application examples are effective, not the rated part spec
2. 1x4.7uF and 2x220nF "effective ceramic caps" are recommenced on the input.
The webench design seems to disagree with the datasheet on two points:
1. A single 4.7uF 50V capacitor is recommended. In my application at 36V VIN, this capacitor will derate to probably ~1uF or less. The datasheet requires 4.7uF of effective capacitance I will need at least 4 of these 4.7uF capacitors to provided the needed capacitance with derating considered (or perhaps a 1-2 larger caps, maybe with higher voltage ratings).
2. Webench is suggesting I use two banks of 3x10nF capacitors. This is not even close to the 2x220nF the datasheet suggests.
Additionally, in looking through the webench BOM, I see Cboot is specified as a 10V ceramic cap. The datasheet claims at least a 16V cap is required for this.
Is webench wrong here and I should just follow the datasheet? Or does webench optimize the design in a way that can produce valid results that differ from the datasheet examples?
I tried to link the webench design but the tool isn't loading right now for some reason.
Thank you,
David Gomez
