'The only I can tell you without this information is, that reset pin must be driven properly for Vcc down to 0V. In many datasheets or erratas you can read, that when powering up micro reset pin must follow Vcc from 0V on! So, in most cases 74HCMOS gate will be most advantegous, here.'

Kai, I disagree. The ONLY thing that reliably work for driving the reset pin is a supervisor chip.


Hallo Erik,

since many months (or even years) we both recommend in forums always to use a proper supervisory chip. And I many times stated, that a MAX1232 is very good choice.

May be I was not concrete enough: I would never build a discrete reset circuit, as long as those nice reset controllers are available. But I responded to Fahmy, who wanted to know which of digital families is the more suited one. And as 74HCMOS operates down to about Vcc=1V, this would be a more suited candidate than 4000CMOS series e.g., if he so wants to build a discrete solution.

In any case, some additional measures would be necessary, when fabricating a discrete reset circuit. E.g. BS250 and BS170 enhancement VMOS transistors in combination with some adequate pull-ups can be used to guarantee reliable function down to Vcc=0. But, again, why doing this, when MAX1232 and others are available?

Kai