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LT3080 Thermal Shutdown

Hi LT, can you please describe the thermal shutdown mode of the LT3080 LDO. I see on the datasheet 2 figures that describe the SOA and current limits relative to the input - output differential and the current limit over temperature. 

My question is how does the thermal shutdown differ from the current limit? and what is the resulting operational effect on the device? Does the device current limit or is the output turned off until the junction temperature is within the datasheet range?

Thanks,
Adam

  • Hello,

    thermal shutdown is a protection function and acts as the last line of defense to protect part from destruction. Do NEVER EVER CALCULATE your operating conditions with overtemperature protection as valid operation state.

    Current limit is measured during operation and LT3080 reacts accordingly when exceeded.

    But, depending on the operation conditions (Vdrop, Iout, ambient temperature), thermal shutdown might be triggered before current limit is achieved and vice versa.

    Current limit will be adjusted by the LT3080 according to the Vin-Vout difference:

    If LT3080 junction temperature is below overtemperature threshold current limit will act accordingly to its name, it will limit the output current and tries in parallel to keep the output voltage as close as possible to the given setpoint.

    Overtemperature protection will disable the output (and most of the LT3080 circuitry). The overtemperature threshold temperature is beyond the specified temperature range.