WEBENCH® Tools/LM2841: Why the result of WEBENCH is different with datasheet of LM2841?

Hao,

The inductor and output cap is a function of ripple current, input/output conditions and the frequency of operation of the device. In addition, the tool accounts for stability for the entire range of input voltages which will lead to different solutions from datasheet, typically, larger Cout values compared to datasheet.

You can start with datasheet design if you like but please check the operation of the design across all corners on an evaluation board to ensure you it works as expected. Please make sure you are using the correct version of the IC. For example the LM2841X will be lower frequency version(550kHz) so will result in bigger inductor and cap as compared to LM2841Y which is higher frequency version (1.25MHz).

Regards,
Amod

Hao,

That particular test shows the DC load settings to be:

Slew Rate: ~2A/msec

Frequency: 2kHz

Duty Cycle: 50%

-Sam

Hao,

The bottom (current) waveform traverses 100mA in ~50us. That's 0.1A / 50us which is equivalent to 2A/millisecond. This is slower than the test we typically do now but it still shows the output voltage response for a typical condition.

-Sam

Heo,

This test was done in 2009, 10 years ago. We did not have specific standards for testing.

You can learn what would happen for a 2A/us test by ordering/testing an evaluation module or using our simulation tools. The results will be similar to the 2A/ms chart with slightly higher overshoot/undershoot.

-Sam