• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 297 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS40170: please help comment reserve how much buffer for max operating temperature

Frank(EP) Liu
Expert 5310 points

Part Number: TPS40170

Hi Sir.,

my customer has below configuration for TPS40170. The operating temperature is a little close to max temperature spec, 125C.

Vin : 50V

Vout: 12.25V /8.5A

Max. Temp we measured: top of IC is 107 degree c, bottom of IC is 104 degree C

can I know normally we should reserve how much buffer for operating temperature?

BR,

frank

  • 0
    TI__Mastermind 34875 points

    Hi Frank,

    How about Ta or board temperature? Did customer evaluate power loss of TPS40170? Normally the controller should not be so hot.

    For TPS40170 in normal application, the design is acceptable if the Tj is below 125C in worst case condition, for high reliability application, there maybe derating on Tj at 10C or 20C in worst case condition. 

    B R

    Andy

  • 0 in reply to Andy Chen
    TI__Expert 5310 points

    Andy,

    IC power consumption is ~1W.

    We have measured in two conditions, at Ta 25C and 40C respectively. Their results are all close to 100C, because the fan flow will vary with environment temp changing.

    It is a little margin by the derating rule, -20C. And we want to know does this affects the IC’s lifetime?

    BR,

    frank

  • 0 in reply to Frank(EP) Liu
    TI__Expert 5310 points

    hi Andy,

    Let me put more information for system.

    -   The ambient temp : 45C (inner system)

    -   IC power consumption: 1Ws

    -   PCB layout: 2-layer, bottom area for heat dissipation is 85mm2 about (refer to below picture)

    do you see anything wrong or risky in design?

    BR,

    frank

  • 0 in reply to Frank(EP) Liu
    TI__Mastermind 34875 points

    Hi Frank,

    This 2 layer board is quite small, the ground plane is not well optimized for TPS40170 heat sinking,  20C derating is acceptable if it's tested at Vin-max, highest Ta and load conditions. 

    B R

    Andy