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Visitor
July 20, 2026
Question

Expected temperature for LD39100PU33R

  • July 20, 2026
  • 1 reply
  • 24 views

In a larger design I’m using a LD39100PU33R for a 3.3V output. The input voltage is 5V and the device has decoupling capacitors as per the datasheet. The 3.3V circuit is consuming about 0.5A and the device is capable of delivering 1A. The circuitry connected is no inductive loads, but rather a steady consumption from sensors (air pressure & temperature).

I am unable to find any information in the datasheet (Section 5. Typical performance characteristics) on what temperature the device will typically be at this load, but it’s running at a constant 75C. This seems to be very high, but how can I know if this is within spec when there is no graph in the datasheet showing current vs temperature?

ref: datasheet https://www.st.com/content/ccc/resource/technical/document/datasheet/72/02/e5/ee/df/36/40/5e/CD00233788.pdf/files/CD00233788.pdf/jcr:content/translations/en.CD00233788.pdf

1 reply

TDK
July 20, 2026

So dissipating 1.7 V at 0.5 A, which is 0.85 W. Multiply that by the thermal data given in the datasheet.

75 C sounds about right. It will depend heavily on the thermal design of the system. It’s ultimately a system parameter, not a chip parameter.

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