WEBENCH® Tools/LM5007: WEBENCH giving alert, even though I am keying AN-1298 components value

Mohd Faizal Abdul Khalek

Part Number: LM5007

Tool/software: WEBENCH® Design Tools

Hi,

I am trying to simulate my DCDC design and WEBENCH giving alert "U1 Junction temperature is too high". Then, I am trying to use the same components value from AN-1298, unfortunately I am still getting the same alert from WEBENCH.

Just to confirm with you if there is issue on the WEBENCH for LM5007?

Thanks,

over 5 years ago

0 Marshall_Beck over 5 years ago

TI__Mastermind 35210 points

Be share circuit and webench results in the thread.

What is the reported loss in the converter?

What are the power conditions?

0 Mohd Faizal Abdul Khalek over 4 years ago in reply to Marshall_Beck

Prodigy 30 points

Hi Marshall,

I am trying to simulate circuit below which I referred to LM5007 datasheet (Figure 7). Unfortunately, when I set Ron = 200KHz, there is warning alert mentioned that the junction temperature is too high. You can refer to webench chart shows on Figure 1 for junction temperature.

So, my question is, which one I need to refer at? i.e Datasheet Typical Application or Webench Power Designer?

Figure 1 - Junction Temperature

0 Marshall_Beck over 4 years ago in reply to Mohd Faizal Abdul Khalek

TI__Mastermind 35210 points

Hell you can see that for 75V input, max junction temperture is exceeded.

If your were operating at 75V input, continuously, this would be a concern, but not so much for transient, perhaps.

What is typical input voltage? I would base estimated thermal calculations off that.

0 Mohd Faizal Abdul Khalek over 4 years ago in reply to Marshall_Beck

Prodigy 30 points

Hi Marshall,

My application running at 72V input continuously.

Just wonder, why the application notes suggest user to use Ron = 200K for Vin = 75V?

0 Marshall_Beck over 4 years ago in reply to Mohd Faizal Abdul Khalek

TI__Mastermind 35210 points

hello Mohd,

While these converter can support 75V, losses correspond to temperature rise in the IC.

For 75V input, switching losses will be high.

Also, loss in external catch diode will be high for large step down ratio.

Another solution may want to be considered, such as controller with external FETs. External FETs can be optimized.

I am curious, can you please share webench report? I am curious to know report power dissipated in IC. I can do rough calculation and compare.

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WEBENCH® Tools/LM5007: WEBENCH giving alert, even though I am keying AN-1298 components value