HV detect app note circuit issues. – Can you spot some plroblems with this circuit? 2

This morning, I found this T.I. app note and saw issues. They aren’t exactly subtle. For fun, I am posting here. What would you catch about this during a table top design review?

https://imgur.com/a/GUN1w2r



View Reddit by Danner1251View Source

2 Comments

  1. They used a “~” for the “supply” symbol instead of a DC source symbol. Other than that, I can’t find any problems.

  2. Things I am not crazy about:

    1) No bandwidth limiting on the input, leaving open suscepability to false triggering on R.F. or noise.

    2) No C across Z1. This would improve the dynamic (AC) response of this reference.

    3) Zeners may have have significant tempcos. A bandgap reference instead, would be better here.

    4) More subtle, R4 is high enough that when combined with Cgs, T1 turnon/off may be too slow.

    5) A resistor across Z2 would negate their first design note so this comparator 𝒄𝒐𝒖𝒍𝒅 be open collector (/drain). I like setting a parallel resistor across Z2 such that Vgs is not exceeded in the off chance that Z2 would fail open.

    Fun stuff!

    πŸ˜‰

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