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TPS40057: TPS40057 OTP isssue

Part Number: TPS40057
Other Parts Discussed in Thread: TPS40055EVM-002, LM25145, LM5145, LM73605

Hi Sir

I have a design use TPS40057 for DC/DC module vin18~30 vout: 15/3A.

When vin:30V IC temperature is 140C  Efficiency 94% but ic was not protection.

Does TPS40057 has OTP function?

  • Joey,

    TPS40057 does have over temperature protection. The activation point is 165 C nominal. Since TPS40057 is a controller, most of the power dissipation should be in the external FETs. It would be unusual for the IC temperature rise to be that high at room temp ambient.
  • John,

    Because it module so PCB size is very small ,I will try TPS40055EVM-002 OTP function.
  • If this is a new design, we'd recommend a newer controller: LM25145, or LM5145 for higher Vin range.

    If the PCB size needs to be small, you can also consider a synchronous buck LM73605. It is a 36V max input voltage, 5A part. The efficiency with 12V output voltage is given on the datasheet. Powerloss is similar with 15V output voltage for quick estimation. Synchronous buck has both FETs integrated inside the IC, so the total solution size is smaller. The drawback is that heat is also generated from one IC and carefully design PCB is needed to provide good heat dissipation path. Please follow the directions at the PCB layout session for good thermal design.

    Regards,

    Yang
  • Hi Yang:

    I use TPS40055EVM-002 try OTP function, but temp over 160C OTP function have not started.
  • How many units have your tried? The OTP threshold is not a very precise parameter, there will be part to part variations.

    How did you measure the junction temperature? Can you let the junction temperature continue to rise higher to check when the OTP will be activited?

    Regards,

    -Yang
  • Hi Yang:

    I use Heat Gun then measure IC face temp .

    If I rise higher else component will fail this test meaningless.
  • This is not an accurate way to measure the die temperature. The surface temperature would be higher than the die. Yes, you might de-solder some components before the die is heated high enough.

    The TPS40057 is a controller, the temperature rise on it due to heavy loading wouldn't be as much as the power switches. What is the max ambient temperature you need?