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LMQ61460-Q1: Efficiency to temp relationship and Junction temp(max) derating(10year)

Roy Chou1
Genius 14385 points
Part Number: LMQ61460-Q1

Hi Team,

Ford request my customer provide the simulation of efficiency with same load, but different ambient temp. For example,

Vin = 13.5V

Vout = 3.3V

Fsw = 400kHz

Iout = 1.8A

Tamb(-40C~85C)

They would like to have the chart of efficiency to ambient relationship. May we provide it by using simulation?

In addition, they would like to know if our Tj-max(150C) whether has derating effect after ten years? Maybe Tj(max) become 150C@80%

Regards,

Roy

  • 0
    TI__Guru 50120 points

    Hello Roy,

    I need to check with the validation team to get some dataset of the efficiency over temperature.

    I plan to get back to you by Friday (2/2/2024) PST timeframe. 

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    TI__Guru 50120 points

    Hello Roy,

    Please refer to the efficiency result up to 4A over temperature. 

    I've boxed the efficiency at 1.8A for your reference.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    TI__Genius 14385 points

    Hi Jimmy,

    For the simulation tool, can I access it? 

    Excuse me, we also need 7Vin and 18Vin chart. Is it possible the list the value for us? Thank you.

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Genius 14385 points

    Hi Jimmy,

    In addition, they would like to know if our Tj-max(150C) whether has derating effect after ten years? Maybe Tj(max) become 150C@80%

    Do we have the spec?

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Guru 50120 points

    Hello Roy,

    The results previously shown are actual validation data taken on 2 units and not simulated results. 

    You can use WEBENCH Designer tool to get the simulated data at room and then assume that worse case is at hot. This is because at hot the internal mosfet resistance increases which results in more power losses through the FETs.

    For the derating effect I will need to ask a product engineer that question and if there is any data/report on this. Will get back to you once I get more information from them.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    TI__Genius 14385 points

    Hi Jimmy,

    Thanks for information. I tried to use webench to simulate the Vin = 7V condition, but failed. May you help check it for me?

    Below is the result that I used webench to simulate so far. I recommend to record the IC Pd and total efficiency because inductor is different from my customer.

    TAMB= -40C

    Vin

    Vout

    FSW

    Loading

    Efficiency？

     

    7

    3.3

    400KHz

    1782mA

     

     

    13.5

    3.3

    400KHz

    1782mA

    234.09mW(93%)

     

    18

    3.3

    400KHz

    1782mA

    270.02mW(92.5%)

    TAMB= 25C

    Vin

    Vout

    FSW

     

     

     

    7

    3.3

    400KHz

    1782mA

     

     

    13.5

    3.3

    400KHz

    1782mA

    291.51mW(92.1%)

     

    18

    3.3

    400KHz

    1782mA

    332.51mW(91.6%)

    TAMB= 85C

    Vin

    Vout

    FSW

     

     

    7

    3.3

    400KHz

    1782mA

     

     

    13.5

    3.3

    400KHz

    1782mA

    291.7mW(92.29%)

     

    18

    3.3

    400KHz

    1782mA

    332.7mW(91.6%)

    TAMB= 110C

    Vin

    Vout

    FSW

     

     

     

    7

    3.3

    400KHz

    1782mA

     

     

    13.5

    3.3

    400KHz

    1782mA

    291.79mW(92.2%)

     

    18

    3.3

    400KHz

    1782mA

    336.64mW(91.6%)

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Guru 50120 points

    Hello Roy,

    To get around this, you should set the Iout Max entry to 6A and change it in the operating values. 

    Then you can change the current of the application back to 1.8A on the "operating values" tab of the "Customize" section.

    Since the inductor used for the application will always be based on the maximum rated current of the device, not the max current of application, the inductor will always be rated for 6A. 

    https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=13AC5E93EA11D0E3

    jimmy