i want to design a internal time reference, with no qurzt.
now i am considering to have a temperature independent current source, and then
charge the capacitor. how accurate can this time reference be??
What you want already has been built within a 555 timer. All you need is to put a stable voltage On it, it has all other circuits including comparator and flip-flop. But again all it depends what accuracy we are talking about, surely a crystal oscillator will be much more accurate.