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In some power supplies there is OTP functionality mentioned as in the example (from this datasheet) below:

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In this case, what does 80°C mean? Does it mean the PSU output will shut down when the ambient temperature becomes 80°C or when its PCB temperature becomes 80°C?

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  • \$\begingroup\$ That’s up to the manufacturer. Probably heatsink temperature. \$\endgroup\$
    – winny
    Sep 6 at 7:53
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    \$\begingroup\$ It's when the sensor (probably NTC) is at 80C. Without doing a strip down of the power supply, we don't know where the sensor is located. If well designed it'll either be at the hottest part of the PSU, or the most sensitive part of the PSU. \$\endgroup\$
    – Puffafish
    Sep 6 at 8:24
  • \$\begingroup\$ It is most likely measured at the main switcher transistor (both sensor and transistor mounted on a heatsink). When the current demand is too high, it will heat up to a specific level that, when exceeding 80C will shut down the PSU \$\endgroup\$ Sep 10 at 1:00

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