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Original question:

LM73606-Q1: thermal test results

LM73606-Q1: thermal evaluation

Arie Li
Expert 3390 points
Part Number: LM73606-Q1
Other Parts Discussed in Thread: LM61460-Q1, LM62460-Q1

Hi team,

 

Could you please help to analyze whether LM73606-Q1 will have thermal issue under below application?

 

Vin: 6-16V

Vout: 5V

Iout: 6A

Frequency: 2.2MHz

Ambient temperature: 85C

 

I have a rough calculation and feel concerned about the thermal performance. So I would like to check with you whether there would have thermal problem in this application. Could you please help to analyze? BTW, how you usually do to evaluate the thermal performance of this device, do you have any tools or test results? Thank you.

 

BR,

Arie

  • 0
    TI__Expert 3835 points

    Hi Arie,

    Thermal performance is heavily reliant on board layout and size. If you look at figure 96 of the datasheet you see an RTJA across copper area and board layers. 

    After you determine the RTJA estimate the junction temperature with equation 30. Based on eff curves, we should expect around 90% efficiency. With only 40 degree for junction rise, the board TJA needs to be around 15 TJA. 

    Regards,

    Ethan

  • 0 in reply to Ethan T
    TI__Expert 3390 points

    Hi Ethan,

    Thank you for your reply. I noticed the figure from datasheet, to achieved 15 board TJA, customer should use at least 4 layer board with 70*70 copper area, right? The copper area means the total area of ground copper, right? Will it be a challenge for layout design? Besides this device, do you have any other recommendation for this application? Should customer switch to a Buck controller? Thank you.

  • 0 in reply to Arie Li
    TI__Expert 3835 points

    Hi Arie,

    Yes, I would assume atleast the 2nd layer and bottom layer are mostly ground copper. This would be a more difficult layout design than usual.

    I recommend taking a look at LM61460-Q1 or LM62460-Q1(http://www.ti.com/lit/ds/symlink/lm61495-q1.pdf ) .Both devices are characterized up to 150C so there is more margin for  the junction temperature. Please email me personally for more information on LM62460-Q1.

    If these devices do not fit, then going into controllers may be the solution.

    Regards,

    Ethan