WEBENCH® Tools/LMS3655-Q1: Vin Min is high

Hi Kim,

This device has a maximum duty cycle limit of 98%. For the above condition, the maximum duty cycle is being hit (minimum off time 65ns). The duty cycle on WEBENCH is calculated considering the voltage drop across the inductor DCR and Rdson of the high side and low side MOSFETs.Please either reduce the Vout or increase the input Voltage.

Thanks & Regards,
Praveen B

Hi Praveen

Thanks for your answer.

The datasheet suggests running at 5.6V (see highlighted):

7.7 System Characteristics:

When changing my test condition to match (3.5A) it could go down to 6.3V but I am still puzzled about the difference (5.6V in datasheet and 6.3V in WEBENCH). Are datasheet 'test conditions' calculated using ideal components rather than real life tests?

Best regards
Kim

Hi Kim,

The design should be created for Vmin=5.6V as per the datasheet for the given components(Non-ideal) and test conditions. We have fixed this issue. You will able to create the design for Vmin-=5.7V since different components are selected on WEBENCH( Variation of Rdson and DCR values). The fix will be available on ti.com by mid of the next week. We will keep you updated on the same.

Thanks & Regards,

Praveen B