I have a turn-on sequence problem for my dual power (3.3/1.2V) IC.
1.2V must started before 3.3V. Does anyone have good idea to reach that?

I know there are some reset ICs can do that ,but the price is first priority.

3.3V and 1.2V comes from regulation of 5V.
The max amp. of 3.3V and 1.2V is 400mA.

 

You can use a 555 timer IC and small relay to delay the 3.3 voltage to get into the circuit. Or, you can you the technique provided in the LM317 voltage regulator for slow rise of the regulated output.

 

Thanks your reply. And I think the second method is better for me due to economic reason.
I will appreciate you if you tell me how to adjust the regulator rising time?

Thanks.
Joseph Hsu

 

You can use different capacitor values.