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UA78M: no output in - 50°C

Part Number: UA78M
Other Parts Discussed in Thread: TLV2217, , UA78

Hi team,

  1. UA78M33C is used for two Main boards.

  2. After the two main boards are placed at - 50°C for 5 minutes, it is powered on. Both UA78M33C have input but no output. When it is gradually heated to - 15°C , it has 3.3V output.

  3. Replace the UA78M33C with TLV2217-33 in these two boards, Two boards can output normally at - 50°C .

  4. Could you please analysis why this happen?

    What is the difference between UA78M33C and TLV2217-33?

Best Regards

Wesley Huang

  • Hi Wesley,

    The UA78M has a recommended operating temperature range of -40 to 125C. I suspect that below -40C the bandgap reference circuit is having an issue with starting up. The TLV2217 is a newer device (1992 vs the UA78 being released in 1976) so it may have a more robust bandgap circuit but its datasheet only recommends operation down to 0C. 

    Our next-generation linear regulator the TLV767 is even more robust. 

    I hope this answers your question.