LM5122: LM5122 output capacity

Hi Eric,

LM5122 should be suitable for a 36V/120W output.
Do you know the input voltage range?
Based on this we can calculate the necessary duty cycle to check if it is within the LM5122 capabilities.

Best regards,
Niklas

The input voltage is 12V,

I used the Webench to do a simulation for this, you can see the below picture, is this ok? BTW , do we have a better tool just like the webench for the power simulation 

Sincere thanks 

BTW , 

does the LM5122 support the 100% duty cycle? If not, pls help to explain the reason 

Hi Eric,

I do not see an image attachment.
But I can already confirm LM5122 is the best fit for this application with 12V input voltage.
Using webench for design help is okay as well. For some initial calculations, I can also recommend our power stage designer tool:
https://www.ti.com/tool/POWERSTAGE-DESIGNER
There is also a quickstart calculator tool in the working, but this tool might take another two week to go online on the product page.

Regarding 100% duty cycle, do you mean 100% on-time of the high side gate?
Then the answer is yes.
LM5122 has a bypass mode feature, which turns on the high side FET when Vin rises above the Vout target.
The datasheet lists a section on this feature.

Best regards,
Niklas

Hi Niklas,

sorry for forgetting to attach the image but you have answered my question.

BTW , for the boost circuit,is it easier than the buck circuit to get the 100 % duty cycle,cause the buck need the charge pump when output voltage is close to input voltage 

Hi Eric,

The LM5122 uses a charge charge pump as well to be able to support 100% on-time of the high side FET.
There is only a difference when using an asynchronous boost device, where the high side FET is replace by a diode. Then no charge pump is necessary, but the diode losses are also present at all times.

Best regards,
Niklas