WEBENCH® Tools/LM2731: LM2731 efficiency calculation in WEBENCH

Zack Liu

Part Number: LM2731

Tool/software: WEBENCH® Design Tools

Hi Team,

When simulating the LM2731 in WEBENCH, the working condition is: Vin= 4-8V, Vout=11V, Iout=30mA, the simulation result shows the efficiency is 91.9%.

However, if using LM27313, the simulation result shows efficiency is less than LM2731. It is only 75%. Why there is so big difference?

over 3 years ago

0 Bhushan Waghmare over 3 years ago

TI__Expert 3320 points

Hi Zack,

At first glance it looks like we have different external diodes selected for LM2731X and LM27313. As component is different, there should be difference in efficiency. We will investigate the huge difference and get back to you.

Best Regards,

Bhushan

0 Zack Liu over 3 years ago in reply to Bhushan Waghmare

TI__Mastermind 34201 points

Hi Bhushan,

Thanks for the quick reply.

In the LM2731 datasheet, there is efficiency curve figure 16 for X option and figure 23 for Y option. The 30mA efficiency is much less than 91.9% if fsw = 1.6MHz. The 30mA efficiency will higher if using fsw=600kHz option. So please check in the formula the fsw is 1.6MHz, not 600kHz.

0 Bhushan Waghmare over 3 years ago in reply to Zack Liu

TI__Expert 3320 points

Hi Zack,

Thanks for your patience here. We have looked into the issue and found the root cause. Team is working on the fix. We will let you know once the fix is available on ti.com

Best Regards,

Bhushan

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WEBENCH® Tools/LM2731: LM2731 efficiency calculation in WEBENCH