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Surely it will: When VDD is switched on (even if it rises slowly), C initially provides the necessary startUp current. The limiting R isn't necessary, IMHO, because the pmos limits the current anyway.PaloAlto said:... If all the nodes are zero, it will never startup
erikl said:Surely it will: When VDD is switched on (even if it rises slowly), C initially provides the necessary startUp current. The limiting R isn't necessary, IMHO, because the pmos limits the current anyway.PaloAlto said:... If all the nodes are zero, it will never startup
erikl said:Surely it will: When VDD is switched on (even if it rises slowly), C initially provides the necessary startUp current. The limiting R isn't necessary, IMHO, because the pmos limits the current anyway.
Right: If you want to switch on the circuit several seconds after switching off, you should spend a (very) hi-ohmic resistor in parallel to the cap to discharge it.frankliner said:I would not use this. The cap can store charge so relying on it always being low at startup is a bad idea.
Thanks a lot.keith1200rs said:I think the value depends on the possible leakage you need to overcome and the rate of rise of the power supply. Normally when designing such circuits I deliberately add in an excessive amount of leakage & check the circuit doesn't work. Then add the startup circuit with the slowest power supply rise you expect and make sure it then works.
Keith
Hi Keith,could you explain it in detail?Why we should pay special attention to the highest OP temperature?keith1200rs said:Remember to check at the highest operating temperature.
Keith